Repeating (one more time) from the May 17th posting, our latest weather-climate discussion for the ESRL/PSD MJO international web site has been posted dated May 17, 2006. Please see
http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html
to view it.
Also, the following is a link to our recently accepted paper by MWR which discusses the GSDM (Weickmann and Berry 2006).
http://www.cdc.noaa.gov/MJO/Predictions/wb2006.pdf
To get the most from these postings, I kindly recommend that at least some perusal of our paper be given. The gist is from taking into consideration the interactions of 4 different subseasonal time scales, a sequence depicting a coherent set of repeatable events has been derived. This set is broken up into 4 stages, referred to as GSDM (for Global Synoptic-Dynamic Model) Stages 1-4 in the text of my Blog. Figure 13 in our paper presents a schematic of the GSDM.
With the exception of a cool region just off the coast of South America, SSTs across most of the central and east equatorial Pacific remain slightly above average, with anomalies ~ plus .5C to even 1.0C around the date line. SSTs range from ~22C at the South American coast (anomalies roughly minus 3C) to around 31C just south of the equator at 160E (recall that we use SSTs of 29C as a threshold for supporting persistent tropical convection). SSTs of 29C and higher also extend from the southwest Pacific into the IO. At depth, as was true about 2-3 weeks ago, anomalies around plus 1-2C extend from 50-250m east-west along the equatorial cold tongue, meaning a slightly deeper than normal oceanic thermocline. SSTAs from the IO into the west Pacific are at least plus .5-1C, with the South Pacific horseshoe experiencing ~ plus 1-2C. The Caribbean into much of the north tropical and equatorial Atlantic Ocean basin also has SSTAs ~ plus 1-2C. Finally, plus 1-2C SSTAs are also present along the southwest coast of Africa and from the east coast of Africa into much of the South IO. Latest prediction from CPC expects ENSO-neutral conditions to prevail during the next 3-6 months (see latest TAO data here, ESRL/PSD data here ). The following are links to ENSO discussions.
http://www.cdc.noaa.gov/people/klaus.wolter/MEI/
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.html
The signal from the MJO remains weak. In general, the global character of the tropical convective forcing has become somewhat unclear during the last few days. Per time-filtered Hovmoller plots of OLR and OLRA (see http://www.cdc.noaa.gov/map/clim/olr_modes/), other variations of tropical forcing have been important during the last few weeks. For instance, while recent enhanced convection along both the East Pacific and Atlantic Ocean ITCZs appears to be linked to a convectively coupled Kw, a convectively coupled Rossby mode has lead to above average rainfall across most of the Arabian Sea (weekly averaged OLRAs ~minus 70-90 W/m**2 in the latter area). This Rossby mode not only may have contributed to the formation Typhoon Chanchu a few weeks ago, but perhaps to the early onset of the active phases for the Indian and Southeast Asian Monsoons. Monitoring tools such as Hovmollers of velocity potential (CHI) and animations of CHI and OLRA weakly support the notion of the tropical convective forcing still being in the EH (see
http://www.cpc.ncep.noaa.gov/products/intraseasonal/vpot_tlon.html and
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ir_anim_monthly.shtml )
Real-time satellite imagery does suggest convection is beginning to increase across portions of western Indonesia and even the central Pacific Ocean especially just north of the Polynesian Islands (due to warm SSTs). Tropical convection remains quite intense from Southeast Asia into the Bay of Bengal and the Arabian Sea. Interestingly, much of interior India as well as the equatorial Indian Ocean remain suppressed. Satellite imagery and other information can be found from the following links: eastern hemisphere, full-disk west Pacific, mtsat, IO, Africa; other imagery here; tropical cyclone statements http://www.nhc.noaa.gov/; the latest 3-day averages of OLR total and anomalies, and other data can be found here.
Statistical and numerical models of the MJO (see ESRL/PSD MJO tools , BMRC MJO tools, CPC MJO tools) are generally inconclusive given the weak MJO signal. However, empirical forecasts from the time filtered coherent modes technique do suggest an eastward propagating signal from the North IO through much of Indonesia through week 2.
My feeling is that we are seeing, in some sense, the tropical convective forcing reorganizing in the presence of the seasonal cycle (including the onset of the EH monsoon systems). I think it is only a matter of short time before the very warm SSTs from Indonesia into the southwest Pacific force tropical convection which will have consequences for the global circulation. Should the equatorial regions from the Maritime Continent (MC) into the western Pacific become the dominant area of tropical convective forcing during week 2, that would represent an eastward (and southward) shift from what is now present. That is, we may see a shift from the loose area currently centered ~15N/90E to an intense concentrated region centered ~5N/130E, lending some truth to the empirical method. The west Pacific convection may combine with the Indonesian thunderstorm clusters while the Southeast Asian Monsoon continues. A MJO signal may evolve out of this possible enhanced region of ~MC tropical forcing.
The interplay between SSTs, tropical forcing and circulation response-feedbacks is ongoing. Zonal mean upper tropospheric anomalous westerly flow has propagated off the equator (mainly into the Southern Hemisphere (SH) due to the seasonal cycle) and is being replaced by easterlies as I type. Per time-latitude sections of 200mb zonal mean zonal wind anomalies, westerly anomalies ~15m/s have propagated into the SH extratropics with ~5 m/s or so moving into the NH. Roughly 5-10 m/s zonal mean easterly anomalies are now present throughout the global tropical and subtropical atmospheres. Plots of recent daily mean 150mb and 250mb vector wind anomalies still present a signal of twin subtropical anticyclones centered ~ 40 deg. east longitude, where twin cyclones were a few weeks ago. These IO twin anticyclones have been linked to rapid wave energy dispersions affecting the PNA sector for about a week. One consequence has been an anticyclonic wave breaking event of a large blocking structure near Alaska, helping to flux AAM out of the subtropics. For the USA, this complexity lead to the western states trough of the past several days.
AAM anomalies are ~ minus 1 standard deviation below the 1968-1997 climatology, with anomalous zonal mean easterly flow across the subtropics and midlatitudes of both hemispheres (particularly the SH). AAM tendency has returned to near zero based on the reanalysis data, which lags 3 days from the current time. The operational data plot shows that AAM has decreased to 2 standard deviations below the 1979-1998 climatology (see http://www.cdc.noaa.gov/map/images/aam/glaam.gif), and I would expect the current AAM tendency to once again be negative (see reanalysis AAM tendency plot ).
In addition to the tropical forcing getting better established across the EH, other components within our GSDM framework contributing to the decline in AAM include the mountain and frictional torques (see plot for mountain torque and plot for the frictional torque; see http://www.cdc.noaa.gov/map/clim/aam.rean.shtml for all AAM plots). A general global mountain/friction torque index cycle has been going on since early April (loosely with mountain torque going up and frictional torque going down) while global mountain torque has been undergoing ~ 25 day variations. The latter include contributions from north-south mountain ranges such as the Andes and those present across East Asia. I would expect the East Asia mountain torque to soon become negative given the anomalously low mean sea level pressure in that region. The point is there is still westerly flow being removed from the atmosphere by the earth both in the zonal mean and global sense.
GSDM Stage 1 still best describes the global circulation at this time. The tropical convective forcing returning into the EH and consolidating ~ 0/100E (see http://www.bom.gov.au/bmrc/clfor/cfstaff/matw/maproom/OLR/map.prevweek.gif) around a week ago helped with establishing Stage 1. Now, I think the circulation working with the warm SSTs is going to re-establish more robust EH tropical convective forcing (as discussed above). Again, one must always think in terms of forcing, response and feedbacks with some understanding of the dynamics.
I also think there is a possibility for the Indonesian convection to start shifting toward the western Pacific during later week 2 into week 3, possibly as a MJO. Within the GSDM framework, a transition to Stage 2 would be probable if this occurs. I have discussed this possibility during at least my last 2 Blogs, and I am going to stay with it. Most ensemble prediction systems (EPS) do not show this since models cannot predict tropical convection very well after about 4-5 days. As I stated in my previous posting, forecast uncertainty is higher than has been true recently. Sources include tropical convective flare-ups from other ocean basins such as the North Atlantic and the roughly 25-day variations of the global mountain torque, especially from the Andes Mountains this time of year.
In the outlooks that follow, I am keying on a possible intensification of the tropical convection ~ the MC during week 2, possibly shifting toward the west Pacific warm SSTs as a MJO during week 3. I am also considering the mountain/frictional torque index cycle and ~ 25 day variations of at least the east Asian mountain torque. All of these components may be increasing by week 3 (seasonal cycle and other considerations understood).
Week 1 (1-7 June 2006): GSDM Stage 1 is most probable. I think we are seeing a summer time rendition of this Stage given shorter wavelengths. As all models generally show with low ensemble spreads, the pattern of an east Pacific trough, Rockies to Great Plains ridge and East Coast trough is likely. There will be at least a couple of short-wave troughs moving along the relatively strong westerly flow just north of the ridge. This pattern translates to above normal temperatures and below normal precipitation for about the western 2/3 rds of the country with the opposite for the East. Excessive heat may become a concern for portions of the Intermountain West and Plains (understanding dewpoints will be generally low) with heavy rainfall for portions of the East and Northeast. Finally, some severe local storm and MCS activity is likely for especially the northern Great Plains into the Great Lakes/Ohio Valley states.
Week 2 (8-15 June 2006): The beginning of this period may be similar to week 1. However, as discussed above, a transition to GSDM Stage 2 may be probable. Like was observed during especially the summer of 2004, that situation tends to favor cool/wet across the central part of the country with warmth/dryness along the west coast and southeastern USA (please see
http://www.cdc.noaa.gov/people/klaus.weickmann/disc073004/wx_climate_disc.final.html for example).
This type of pattern can be a prolific producer of heavy rainfall and severe local storms from roughly the eastern Rocky Mountain States of Colorado-Montana through the Central/Northern Plains, Mid/Upper Mississippi Valley into the Great Lakes and Ohio Valley regions.
Week 3 (16-22 June 2006): GSDM Stage 2 continuing and/or emerging would be most probable.
Specifically for Southwest Kansas, we had better hope that there is some truth to my outlook for weeks 2-3, or we may remain “hot and dry forever”. Well above average temperatures and little precipitation is a good bet through most of next week. Yes, hopefully there will be an opportunity for rainfall tonight (5/31) and other things can occur this time of year to get a few storms. If we transition to GSDM Stage 2, our rain chances will increase and temperatures will cool down. That transition may start next weekend.
Latest CDC Ensemble Forecast
Latest NCEP Ensemble Forecast
Additional NCEP Ensemble Output
Latest Canadian Ensemble Output
Latest Deterministic ECMWF Forecasts
http://www.cdc.noaa.gov/people/jeffrey.s.whitaker/refcst/week2/
Please see the CPC Drought Monitor for areas of dryness and the latest official outlooks and statements from Storm Prediction Center not only for severe storms, but also fire weather concerns. Finally, the CPC USA Hazards Assessment for offers additional insights not only for possible week 1 high impact weather, but week 2 as well.
I will attempt another posting sometime this upcoming weekend.
Ed Berry
Wednesday, May 31, 2006
Saturday, May 27, 2006
Catching Up With the Atmosphere
Repeating from the May 17th posting, our latest weather-climate discussion for the ESRL/PSD MJO international web site has been posted dated May 17, 2006. Please see
http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.htmlto view it.
Also, the following is a link to our recently accepted paper by MWR which discusses the GSDM.
http://www.cdc.noaa.gov/MJO/Predictions/wb2006.pdf
I have been on a lot of travel since my last posting on May 17th, and am catching up on the current situation. The following is briefly what I have learned so far.
SSTs across most of the central and east equatorial Pacific are slightly above average, with anomalies ~ plus .5C to even 1.0C around the date line. SSTs range from ~25C near the South American coast to around 31C just south of the equator at 160E (recall that we use SSTs of 29C as a threshold for supporting persistent tropical convection). SSTs of 29C and higher also extend from the southwest Pacific into the IO. At depth, as was true about 2 weeks ago, anomalies around plus 1-2C extend from 50-250m east-west along the equatorial cold tongue, meaning a slightly deeper than normal oceanic thermocline. SSTAs from the IO into the west Pacific are at least plus .5-1C, with the South Pacific horseshoe experiencing ~ plus 1-2C. The Caribbean into much of the NTA also has SSTAs ~ plus 1-2C. Latest prediction from CPC expects ENSO-neutral conditions to prevail during the next 3-6 months (see latest TAO data here, ESRL/PSD data here ).
The following are links to ENSO discussions.
http://www.cdc.noaa.gov/people/klaus.wolter/MEI/
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.html
The signal from the MJO remains weak. However, tropical convective forcing has returned into the EH. This behavior was expected 2 weeks ago, along with the current response of the global circulation. Satellite imagery (eastern hemisphere, full-disk west Pacific, mtsat, IO, Africa; other imagery here ) indicates attempted organization with the most robust region of enhanced rainfall extending from the Arabian Sea into western Indonesia, about 5-10 deg north of the equator. The latter reflects the northward shift due to seasonal transition, including the onset of the Indian and South Asia monsoons. A secondary area of tropical thunderstorm enhancement was centered ~0/150E in the region of the very warm west Pacific Ocean SSTs. Finally, some enhanced activity remains from the east Pacific ITCZ into at least northern South America, linked to a convectively coupled Kw. The first named tropical cyclone (Aletta) for the 2006 East Pacific Hurricane season has formed just south of Mexico (see http://www.nhc.noaa.gov/). If interested, the latest 3-day averages of OLR total and anomalies, and other data can be found here.
Statistical and numerical models of the MJO (see ESRL/PSD MJO tools , BMRC MJO tools, CPC MJO tools) are inconclusive given the weak MJO signal. My own suspicion would be for some consolidation of the 2 areas of enhancement discussed above during the next week or so, with some eastward shift afterwards. The seasonal cycle including the Indian and Asian monsoon systems will play a role to whatever evolutionary route the tropical convective forcing takes during the next few weeks.
Since ~ May 14th the interplay between SSTs, tropical forcing and circulation response-feedbacks have lead to a substantial change in the global circulation. For instance, zonal mean upper tropospheric anomalous westerly flow has propagated off the equator (mainly into the Southern Hemisphere (SH)) and is being replaced by easterlies. Anomalous zonal mean easterly flow persists across the subtropics and mid latitudes of both hemispheres. Plots of recent 150mb and 250mb daily mean vector wind anomalies clearly present a signal of twin subtropical anticyclones centered ~ 40 deg. east longitude, where twin cyclones were a couple of weeks ago. These IO twin anticyclones are linked to a rapid wave energy dispersion that is approaching the USA west coast. Finally, also hooked up with the EH tropical convection and baroclinic wave energy dispersion, a large anomalous anticyclonic gyre located around Alaska is breaking anticyclonically helping to flux AAM out of the subtropics.
AAM anomalies are now ~ minus 1 standard deviation below the 1968-1997 climatology, with anomalous zonal mean easterly flow across the subtropics of both hemispheres. AAM tendency is just above a negative minimum (~ 3 standard deviations below the reanalysis climatology; see plot ), with much of that due to the SH frictional torque and north-south mountain ranges including recently the Andes and those across the tropics (see plot for mountain torque and plot for the frictional torque; see http://www.cdc.noaa.gov/map/clim/aam.rean.shtml for all AAM plots). GSDM Stage 1 best describes the global circulation at this time.
As mentioned above, a baroclinic wave packet tied to the EH tropical convection is dispersing across the North Pacific Ocean basin as I type. As most models now show, the most probable response appears to be amplification and progression of the current PNA wave train week 1. During week 2 (well into June), uncertainty becomes higher than has been the case recently for forecasts for ~ weeks 2-3. Sources include the future of the tropical convective forcing not only from the EH, but flare-ups from other basins such as the North Atlantic and western Pacific. Also adding uncertainty are the roughly 20-day variations of the global mountain torque, especially from the Andes Mountains this time of year. My own thought is to key on the tropical forcing from the IO and Indonesia, suggesting GSDM Stage 1 to be most probable during week 2. During week 3 GSDM Stage 2 may evolve. The following outlooks have low confidence for mainly weeks 2-3.
Week 1 (28 May – 3 June 2006): GSDM Stage 1 is most probable, with transient synoptic variations. Initially, the western part of the country will be cooler than normal and unsettled while the central and eastern states have well above normal temperatures (possible excessive heat problems). Severe local storms are a good bet for especially the Central and Northern Plains and Upper Mississippi Valley. As the trough-ridge pattern across the USA moves east, while the western states warm the rest of the country should gradually cool down. The severe local storm hazard is probable to shift into parts of the Southern Plains into at least the Ohio Valley.
Week 2 (4-10 June 2006): GSDM Stage 1 continuing would be most probable. At the start, much of the Intermountain west and Central Plains may see well above average warmth while the rest of the country has near or somewhat cooler than normal temperatures. A situation similar to the present may return for days 10-14 (7-10 June). The wettest areas of the country may include the Pacific Northwest-Northern Plains/Upper Mississippi Valley on into the mid Atlantic and Northeast States.
Week 3 (11-17 June 2006): Given the above average west Pacific SSTs, robust tropical convection may emerge into that region, allowing a transition to GSDM Stage 2. Like was observed during especially the summer of 2004, that situation tends to favor cool/wet across the central part of the country with warmth/dryness along the west coast and southeastern USA (please see
http://www.cdc.noaa.gov/people/klaus.weickmann/disc073004/wx_climate_disc.final.html
for example).
Specifically for southwest Kansas, decent opportunities of rainfall exist through at least the first half of week 1. Overnights Monday night and Tuesday night may feature good MCS activity and locally heavy rainfall (along with the usual severe local storm hazard). By late next week into next weekend, dryer weather should return. Much cooler temperatures are probable by the middle of next week, with maximums perhaps remaining in the 70s for at least a day, only to warm quickly by next weekend. I suspect next weekend will be quite warm and dry, possibly turning windy and hot (with maxes above 100F) again for much of week 2. By that time the westerlies with their troughs are likely to pass well north of us and the Southern Plains may be under a subtropical ridge. Of course, what STJ there is may initiate relatively isolated high based storms along the dryline and higher terrain in general. Let's see if GSDM Stage 2 returns week 3, as discussed above. That circulation pattern is favorable for rainfall across southwest Kansas during the summer.
Latest CDC Ensemble Forecast
Latest NCEP Ensemble Forecast
Additional NCEP Ensemble Output
Latest Canadian Ensemble Output
Latest Deterministic ECMWF Forecasts
http://www.cdc.noaa.gov/people/jeffrey.s.whitaker/refcst/week2/
Please see the CPC Drought Monitor for areas of dryness and the latest official outlooks and statements from Storm Prediction Center not only for severe storms, but also fire weather concerns. Finally, the CPC USA Hazards Assessment for offers additional insights not only for possible week 1 high impact weather, but week 2 as well.
I will try to do an update around Wednesday, 5/31.
Ed Berry
http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.htmlto view it.
Also, the following is a link to our recently accepted paper by MWR which discusses the GSDM.
http://www.cdc.noaa.gov/MJO/Predictions/wb2006.pdf
I have been on a lot of travel since my last posting on May 17th, and am catching up on the current situation. The following is briefly what I have learned so far.
SSTs across most of the central and east equatorial Pacific are slightly above average, with anomalies ~ plus .5C to even 1.0C around the date line. SSTs range from ~25C near the South American coast to around 31C just south of the equator at 160E (recall that we use SSTs of 29C as a threshold for supporting persistent tropical convection). SSTs of 29C and higher also extend from the southwest Pacific into the IO. At depth, as was true about 2 weeks ago, anomalies around plus 1-2C extend from 50-250m east-west along the equatorial cold tongue, meaning a slightly deeper than normal oceanic thermocline. SSTAs from the IO into the west Pacific are at least plus .5-1C, with the South Pacific horseshoe experiencing ~ plus 1-2C. The Caribbean into much of the NTA also has SSTAs ~ plus 1-2C. Latest prediction from CPC expects ENSO-neutral conditions to prevail during the next 3-6 months (see latest TAO data here, ESRL/PSD data here ).
The following are links to ENSO discussions.
http://www.cdc.noaa.gov/people/klaus.wolter/MEI/
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.html
The signal from the MJO remains weak. However, tropical convective forcing has returned into the EH. This behavior was expected 2 weeks ago, along with the current response of the global circulation. Satellite imagery (eastern hemisphere, full-disk west Pacific, mtsat, IO, Africa; other imagery here ) indicates attempted organization with the most robust region of enhanced rainfall extending from the Arabian Sea into western Indonesia, about 5-10 deg north of the equator. The latter reflects the northward shift due to seasonal transition, including the onset of the Indian and South Asia monsoons. A secondary area of tropical thunderstorm enhancement was centered ~0/150E in the region of the very warm west Pacific Ocean SSTs. Finally, some enhanced activity remains from the east Pacific ITCZ into at least northern South America, linked to a convectively coupled Kw. The first named tropical cyclone (Aletta) for the 2006 East Pacific Hurricane season has formed just south of Mexico (see http://www.nhc.noaa.gov/). If interested, the latest 3-day averages of OLR total and anomalies, and other data can be found here.
Statistical and numerical models of the MJO (see ESRL/PSD MJO tools , BMRC MJO tools, CPC MJO tools) are inconclusive given the weak MJO signal. My own suspicion would be for some consolidation of the 2 areas of enhancement discussed above during the next week or so, with some eastward shift afterwards. The seasonal cycle including the Indian and Asian monsoon systems will play a role to whatever evolutionary route the tropical convective forcing takes during the next few weeks.
Since ~ May 14th the interplay between SSTs, tropical forcing and circulation response-feedbacks have lead to a substantial change in the global circulation. For instance, zonal mean upper tropospheric anomalous westerly flow has propagated off the equator (mainly into the Southern Hemisphere (SH)) and is being replaced by easterlies. Anomalous zonal mean easterly flow persists across the subtropics and mid latitudes of both hemispheres. Plots of recent 150mb and 250mb daily mean vector wind anomalies clearly present a signal of twin subtropical anticyclones centered ~ 40 deg. east longitude, where twin cyclones were a couple of weeks ago. These IO twin anticyclones are linked to a rapid wave energy dispersion that is approaching the USA west coast. Finally, also hooked up with the EH tropical convection and baroclinic wave energy dispersion, a large anomalous anticyclonic gyre located around Alaska is breaking anticyclonically helping to flux AAM out of the subtropics.
AAM anomalies are now ~ minus 1 standard deviation below the 1968-1997 climatology, with anomalous zonal mean easterly flow across the subtropics of both hemispheres. AAM tendency is just above a negative minimum (~ 3 standard deviations below the reanalysis climatology; see plot ), with much of that due to the SH frictional torque and north-south mountain ranges including recently the Andes and those across the tropics (see plot for mountain torque and plot for the frictional torque; see http://www.cdc.noaa.gov/map/clim/aam.rean.shtml for all AAM plots). GSDM Stage 1 best describes the global circulation at this time.
As mentioned above, a baroclinic wave packet tied to the EH tropical convection is dispersing across the North Pacific Ocean basin as I type. As most models now show, the most probable response appears to be amplification and progression of the current PNA wave train week 1. During week 2 (well into June), uncertainty becomes higher than has been the case recently for forecasts for ~ weeks 2-3. Sources include the future of the tropical convective forcing not only from the EH, but flare-ups from other basins such as the North Atlantic and western Pacific. Also adding uncertainty are the roughly 20-day variations of the global mountain torque, especially from the Andes Mountains this time of year. My own thought is to key on the tropical forcing from the IO and Indonesia, suggesting GSDM Stage 1 to be most probable during week 2. During week 3 GSDM Stage 2 may evolve. The following outlooks have low confidence for mainly weeks 2-3.
Week 1 (28 May – 3 June 2006): GSDM Stage 1 is most probable, with transient synoptic variations. Initially, the western part of the country will be cooler than normal and unsettled while the central and eastern states have well above normal temperatures (possible excessive heat problems). Severe local storms are a good bet for especially the Central and Northern Plains and Upper Mississippi Valley. As the trough-ridge pattern across the USA moves east, while the western states warm the rest of the country should gradually cool down. The severe local storm hazard is probable to shift into parts of the Southern Plains into at least the Ohio Valley.
Week 2 (4-10 June 2006): GSDM Stage 1 continuing would be most probable. At the start, much of the Intermountain west and Central Plains may see well above average warmth while the rest of the country has near or somewhat cooler than normal temperatures. A situation similar to the present may return for days 10-14 (7-10 June). The wettest areas of the country may include the Pacific Northwest-Northern Plains/Upper Mississippi Valley on into the mid Atlantic and Northeast States.
Week 3 (11-17 June 2006): Given the above average west Pacific SSTs, robust tropical convection may emerge into that region, allowing a transition to GSDM Stage 2. Like was observed during especially the summer of 2004, that situation tends to favor cool/wet across the central part of the country with warmth/dryness along the west coast and southeastern USA (please see
http://www.cdc.noaa.gov/people/klaus.weickmann/disc073004/wx_climate_disc.final.html
for example).
Specifically for southwest Kansas, decent opportunities of rainfall exist through at least the first half of week 1. Overnights Monday night and Tuesday night may feature good MCS activity and locally heavy rainfall (along with the usual severe local storm hazard). By late next week into next weekend, dryer weather should return. Much cooler temperatures are probable by the middle of next week, with maximums perhaps remaining in the 70s for at least a day, only to warm quickly by next weekend. I suspect next weekend will be quite warm and dry, possibly turning windy and hot (with maxes above 100F) again for much of week 2. By that time the westerlies with their troughs are likely to pass well north of us and the Southern Plains may be under a subtropical ridge. Of course, what STJ there is may initiate relatively isolated high based storms along the dryline and higher terrain in general. Let's see if GSDM Stage 2 returns week 3, as discussed above. That circulation pattern is favorable for rainfall across southwest Kansas during the summer.
Latest CDC Ensemble Forecast
Latest NCEP Ensemble Forecast
Additional NCEP Ensemble Output
Latest Canadian Ensemble Output
Latest Deterministic ECMWF Forecasts
http://www.cdc.noaa.gov/people/jeffrey.s.whitaker/refcst/week2/
Please see the CPC Drought Monitor for areas of dryness and the latest official outlooks and statements from Storm Prediction Center not only for severe storms, but also fire weather concerns. Finally, the CPC USA Hazards Assessment for offers additional insights not only for possible week 1 high impact weather, but week 2 as well.
I will try to do an update around Wednesday, 5/31.
Ed Berry
Wednesday, May 17, 2006
Indian Ocean/Indonesian Convection -- Great Plains Severe Convection Relationship?
Our latest weather-climate discussion for the ESRL/PSD MJO international web site has been posted dated May 17, 2006. Please see
http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html
to view it.
The following is taken from Section 2 of this discussion called “Predictive Insights”, with some wording changes to reflect the most updated information. Also, the following is a link to our recently accepted paper by MWR which discusses the GSDM.
http://www.cdc.noaa.gov/MJO/Predictions/wb2006.pdf
SSTAs across most of the central and east equatorial Pacific are within .5 deg C of normal, with SSTs ranging from ~26C near 100W to 29C and warmer just west and southwest of the date line. SSTs of 29C and higher also extend from the southwest Pacific into the IO. At depth, anomalies around plus 1-2C extend from 50-250m east-west along the equatorial cold tongue, meaning a slightly deeper than normal oceanic thermocline. SSTAs from the IO into the west Pacific are at least plus .5-1C, with the Pacific horseshoe experiencing ~ plus 1-2C. The Caribbean into much of the NTA also has SSTAs ~ plus 1-2C. Latest prediction from CPC expects ENSO-neutral conditions to prevail during the next 3-6 months (see latest TAO data here, ESRL/PSD data here ). The following are links to ENSO discussions.
http://www.cdc.noaa.gov/people/klaus.wolter/MEI/
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.html
At this time the signal from the MJO is weak with the WH upper tropospheric divergence signal re-emerging into the IO. Satellite imagery (eastern hemisphere, full-disk west Pacific, mtsat, IO, Africa; other imagery here ) still has enhanced convection extending from the east Pacific ITCZ across tropical South America and into especially central Africa. However, during the last few days there has been a rapid increase in the tropical convection across the very warm SSTs of the central IO particularly near the Bay of Bengal. Tropical convection is less organized from the west Pacific toward Southeast Asia (with the important exception of Typhoon Chanchu; see here). Convection has also become a little better organized along the SPCZ over the warm South Pacific SSTs east of Australia. Suppression, which has been over the IO for a few weeks, has abruptly shifted into the northwest Pacific Ocean (latest 3-day averages of OLR total and anomalies, and other data here ).
Statistical and numerical models of the MJO (see ESRL/PSD MJO tools , BMRC MJO tools, CPC MJO tools) generally support the notion of enhanced convection continuing to organize across the IO from tropical Africa by about early week 2, with suppression generally north of Indonesia. SSTs have also remained slightly above average across portions of the central and southern Indian Ocean (~ plus 1-2C), which can be a precursor to a re-emerging MJO into the EH. Finally, SSTs are ~ plus 1-2C above normal across the tropical southwest Pacific, as well as the subtropical North and South Pacific and Atlantic Oceans. These regions will also contribute tropical convective forcing at times. The seasonal cycle will play a role to whatever evolutionary route the tropical convective forcing takes during the next few weeks.
Since April 28th the interplay between SSTs, tropical forcing and circulation response-feedbacks have produced a situation best described by GSDM Stage 3. Recently, with the intense tropical convection returning to the IO, the global circulation is believed to be transitioning to GSDM Stage 4. Plots of recent daily mean 150mb and 250mb daily mean vector wind anomalies clearly present a signal of twin subtropical centered anticyclones ~ 0 deg. longitude as well as the lingering pair just east of the date line. Twin anticyclones, as part of the lower latitude wave trains which characterize GSDM Stage 4, are also developing ~120E (Typhoon Chanchu is also a contributor). The EH subtropical cyclones have all but disappeared. The North Pacific Jet has retracted (with amplification) during the last several days.
AAM anomalies are ~.5 standard deviations above the 1968-1997 climatology, with anomalous zonal mean westerly flow across particularly the SH tropical and subtropical atmospheres, and the midlatitudes of both hemispheres. Anomalous zonal mean easterly flow exists along ~30N and 30S, as well as the NH polar latitudes. The latter are actually a residual of the "bursting anticyclones" that started in March 2006.
AAM tendency has again become positive (~ 2 standard deviations; see plot ), with much of that due to positive torques from north-south mountain ranges including those in East Asia and the Andes (see plot). The frictional torque remains negative, and will remove the added zonal mean westerly due to the mountains (see plot ). In the context of the GSDM, right now we are seeing a submonthly component helping to maintain existing anomalies. However, with the IO convection intensifying, we believe Stage 4 is most probable by the end of week 1, with a transition to GSDM Stage 1 during the week 2-3 time scale, particularly should the tropical forcing move into Indonesia. Of course, the details (timing, location and amplitude) are unclear after roughly day 3.
For the PNA sector, and particularly the CONUS, a ~140W trough, ~110W ridge and eastern USA trough still looks like a good bet for much of week 1. However, these synoptic features are expected to progress by the end of this period as the circulation evolves into GSDM Stage 4. Nearly all models and their ensembles have locked onto this prediction, especially the CDC and NCEP ensembles. The current high latitude retrogression of anticyclonic circulation wind anomalies extending from the North Atlantic Ocean (leading to a negative NAO) into eastern Canada will be a contributor to the weather across the CONUS not only for week 1, but afterwards as well.
As the North Pacific Jet retracts and interacts with the retrograding anticyclone, a ridge across the central Pacific possibly extending well into the Arctic is probable as week 2 approaches. A downstream stronger trough should begin evolving just off the USA west coast, linking with a STJ extending into the southwest and south central states. A ridge is probable across the central USA as a trough lingers across the east and northeast states. During the week 2-3 time-scale, an active GSDM Stage 1 pattern may return although farther north than March due to the seasonal cycle. Experience tells us that the numerical models will likely struggle again as the tropical convective forcing comes back into the EH, particularly should a GSDM Stage 4-1 transition occur. In fact, inconsistencies between model forecasts have already been increasing during the last 3-5 days.
The following is a breakdown for weeks 1-3. Links to additional model output is given at the end. My confidence in the following overall scenario is about average to even slightly above average; however, forget that with timing, etc., details. As I will continue to say, statements of probability are needed to maximize skill for weeks 1-3 and beyond.
Week 1 (18-24 May 2006): Overall, still not a very active pattern for much of the USA, at least early on. GSDM Stage 4 is most probable during this time. Roughly the eastern third of the country looks to have below normal temperatures while record maximum temperatures are possible for locations such as the Intermountain west and the Front Range extending into the Southern Plains. Most shower and thunderstorm activity will be east of the Mississippi River, with little precipitation to the west. While the Northeast states gradually dry out, rainfall should increase across the Pacific Northwest. Gulf of Mexico moisture transport will improve by early next week, and the possibility for one or two episodes of strong/severe west-northwest flow thunderstorms for the Northern Plains/Upper Mississippi Valley into the Great Lakes/Ohio Valley is a concern. Relatively isolated high-based severe storms may be possible along the dryline from western Nebraska-Texas Panhandle due to the STJ. Finally, record low minimums and late season frost may also be a concern for at least the upper Great Lakes States.
Week 2 (25-31 May 2006): GSDM Stage 4 would be probable by the start of this period, possibly transitioning to GSDM Stage 1 by the end. As Gulf of Mexico moisture transport continues to improve (SSTs are above average there, ~ plus .5-1C), widespread severe local storms may become an issue for much of the central USA, particularly centered on locations such as Nebraska-Iowa on to the north and northeast. Dryline storms may become quite intense across the western High Plains. Warmth should also spread eastward from the Central and Southern Plains into the Tennessee Valley/Deep South. In fact, portions of the South may see record highs with temperatures in excess of 100F along with surface dewpoints at least into the 60s (vertical mixing may limit magnitudes). Near normal to slightly cool conditions may persist across the east and particularly for the Northeast while below normal temperatures spread across the Pacific Northwest.
Week 3 (1-7 June 2006): A transition from GSDM Stage 4-1 and possibly to Stage 2 is a concern for this period and may continue into week 4. That would mean an active southwest flow storm track pattern for the Plains as troughs come into the western states and then move northeast into the Upper Mississippi Valley. Tropical moisture transport from the Gulf of Mexico should be plentiful by this time (if not much sooner). The weather would be similar to what was observed during March, only farther north and west. A focus for severe local storms may occur from the Northern/Central Plains into the western Great Lakes States. If GSDM Stage 2 (with the tropical convection moving into the west Pacific) does evolve by, say, late week 3 into week 4, troughs digging into the central Rockies and High Plains would be more probable. That would allow the storm track to shift farther southward across the Plains, perhaps leading to a situation we saw ~May 5-9.
Specifically for southwest Kansas, the dry pattern is back (was only interrupted). Much warmer temperatures are likely starting ~ May 18, with highs well into the 90s. Starting this weekend into the following week, there may be a strong STJ to contribute to at least isolated high based thunderstorms across the elevated terrain to our west. As these storms move by, lightning and high wind may be more probable than decent rainfall; however, we will see. The main storm track will be shifted north of us, as climatology alone says. Temperatures are likely to remain well above average, with days in the 90s with even a few locations above 100F. By week 2, should GSDM Stage 1 return, that would suggest troughs coming into the Rockies and then moving northeast into the Upper Mississippi Valley. Severe local storms would likely accompany these. However, with the storm track to our north, that could mean “hot, windy and dry” at times. However, with less momentum to mix down I would think at least dryline storms and attendant rainfall would be possible (as discussed above).
Lets see if GSDM Stage 2 returns sometime during early June, as discussed above. For those really hopeful of getting decent widespread rainfall across southwest Kansas for this upcoming warm season, SSTs have been warming across the west central Pacific during the last couple of weeks. That would favor tropical convective forcing to propagate farther east, possibly favoring more persistent GSDM Stage 2 patterns.
Latest CDC Ensemble Forecast
Latest NCEP Ensemble Forecast
Additional NCEP Ensemble Output
Latest Canadian Ensemble Output
Latest Deterministic ECMWF Forecasts
http://www.cdc.noaa.gov/people/jeffrey.s.whitaker/refcst/week2/
Please see the CPC Drought Monitor for areas of dryness and the latest official outlooks and statements from Storm Prediction Center not only for severe storms, but also fire weather concerns. Finally, the CPC USA Hazards Assessment for offers additional insights not only for possible week 1 high impact weather, but week 2 as well.
I will be on quite a bit of travel through Friday, May 26. Thus I may not be able to do another writing on this Blog until Memorial Day weekend (which may be quite stormy for a good portion of the USA).
Ed Berry
http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html
to view it.
The following is taken from Section 2 of this discussion called “Predictive Insights”, with some wording changes to reflect the most updated information. Also, the following is a link to our recently accepted paper by MWR which discusses the GSDM.
http://www.cdc.noaa.gov/MJO/Predictions/wb2006.pdf
SSTAs across most of the central and east equatorial Pacific are within .5 deg C of normal, with SSTs ranging from ~26C near 100W to 29C and warmer just west and southwest of the date line. SSTs of 29C and higher also extend from the southwest Pacific into the IO. At depth, anomalies around plus 1-2C extend from 50-250m east-west along the equatorial cold tongue, meaning a slightly deeper than normal oceanic thermocline. SSTAs from the IO into the west Pacific are at least plus .5-1C, with the Pacific horseshoe experiencing ~ plus 1-2C. The Caribbean into much of the NTA also has SSTAs ~ plus 1-2C. Latest prediction from CPC expects ENSO-neutral conditions to prevail during the next 3-6 months (see latest TAO data here, ESRL/PSD data here ). The following are links to ENSO discussions.
http://www.cdc.noaa.gov/people/klaus.wolter/MEI/
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.html
At this time the signal from the MJO is weak with the WH upper tropospheric divergence signal re-emerging into the IO. Satellite imagery (eastern hemisphere, full-disk west Pacific, mtsat, IO, Africa; other imagery here ) still has enhanced convection extending from the east Pacific ITCZ across tropical South America and into especially central Africa. However, during the last few days there has been a rapid increase in the tropical convection across the very warm SSTs of the central IO particularly near the Bay of Bengal. Tropical convection is less organized from the west Pacific toward Southeast Asia (with the important exception of Typhoon Chanchu; see here). Convection has also become a little better organized along the SPCZ over the warm South Pacific SSTs east of Australia. Suppression, which has been over the IO for a few weeks, has abruptly shifted into the northwest Pacific Ocean (latest 3-day averages of OLR total and anomalies, and other data here ).
Statistical and numerical models of the MJO (see ESRL/PSD MJO tools , BMRC MJO tools, CPC MJO tools) generally support the notion of enhanced convection continuing to organize across the IO from tropical Africa by about early week 2, with suppression generally north of Indonesia. SSTs have also remained slightly above average across portions of the central and southern Indian Ocean (~ plus 1-2C), which can be a precursor to a re-emerging MJO into the EH. Finally, SSTs are ~ plus 1-2C above normal across the tropical southwest Pacific, as well as the subtropical North and South Pacific and Atlantic Oceans. These regions will also contribute tropical convective forcing at times. The seasonal cycle will play a role to whatever evolutionary route the tropical convective forcing takes during the next few weeks.
Since April 28th the interplay between SSTs, tropical forcing and circulation response-feedbacks have produced a situation best described by GSDM Stage 3. Recently, with the intense tropical convection returning to the IO, the global circulation is believed to be transitioning to GSDM Stage 4. Plots of recent daily mean 150mb and 250mb daily mean vector wind anomalies clearly present a signal of twin subtropical centered anticyclones ~ 0 deg. longitude as well as the lingering pair just east of the date line. Twin anticyclones, as part of the lower latitude wave trains which characterize GSDM Stage 4, are also developing ~120E (Typhoon Chanchu is also a contributor). The EH subtropical cyclones have all but disappeared. The North Pacific Jet has retracted (with amplification) during the last several days.
AAM anomalies are ~.5 standard deviations above the 1968-1997 climatology, with anomalous zonal mean westerly flow across particularly the SH tropical and subtropical atmospheres, and the midlatitudes of both hemispheres. Anomalous zonal mean easterly flow exists along ~30N and 30S, as well as the NH polar latitudes. The latter are actually a residual of the "bursting anticyclones" that started in March 2006.
AAM tendency has again become positive (~ 2 standard deviations; see plot ), with much of that due to positive torques from north-south mountain ranges including those in East Asia and the Andes (see plot). The frictional torque remains negative, and will remove the added zonal mean westerly due to the mountains (see plot ). In the context of the GSDM, right now we are seeing a submonthly component helping to maintain existing anomalies. However, with the IO convection intensifying, we believe Stage 4 is most probable by the end of week 1, with a transition to GSDM Stage 1 during the week 2-3 time scale, particularly should the tropical forcing move into Indonesia. Of course, the details (timing, location and amplitude) are unclear after roughly day 3.
For the PNA sector, and particularly the CONUS, a ~140W trough, ~110W ridge and eastern USA trough still looks like a good bet for much of week 1. However, these synoptic features are expected to progress by the end of this period as the circulation evolves into GSDM Stage 4. Nearly all models and their ensembles have locked onto this prediction, especially the CDC and NCEP ensembles. The current high latitude retrogression of anticyclonic circulation wind anomalies extending from the North Atlantic Ocean (leading to a negative NAO) into eastern Canada will be a contributor to the weather across the CONUS not only for week 1, but afterwards as well.
As the North Pacific Jet retracts and interacts with the retrograding anticyclone, a ridge across the central Pacific possibly extending well into the Arctic is probable as week 2 approaches. A downstream stronger trough should begin evolving just off the USA west coast, linking with a STJ extending into the southwest and south central states. A ridge is probable across the central USA as a trough lingers across the east and northeast states. During the week 2-3 time-scale, an active GSDM Stage 1 pattern may return although farther north than March due to the seasonal cycle. Experience tells us that the numerical models will likely struggle again as the tropical convective forcing comes back into the EH, particularly should a GSDM Stage 4-1 transition occur. In fact, inconsistencies between model forecasts have already been increasing during the last 3-5 days.
The following is a breakdown for weeks 1-3. Links to additional model output is given at the end. My confidence in the following overall scenario is about average to even slightly above average; however, forget that with timing, etc., details. As I will continue to say, statements of probability are needed to maximize skill for weeks 1-3 and beyond.
Week 1 (18-24 May 2006): Overall, still not a very active pattern for much of the USA, at least early on. GSDM Stage 4 is most probable during this time. Roughly the eastern third of the country looks to have below normal temperatures while record maximum temperatures are possible for locations such as the Intermountain west and the Front Range extending into the Southern Plains. Most shower and thunderstorm activity will be east of the Mississippi River, with little precipitation to the west. While the Northeast states gradually dry out, rainfall should increase across the Pacific Northwest. Gulf of Mexico moisture transport will improve by early next week, and the possibility for one or two episodes of strong/severe west-northwest flow thunderstorms for the Northern Plains/Upper Mississippi Valley into the Great Lakes/Ohio Valley is a concern. Relatively isolated high-based severe storms may be possible along the dryline from western Nebraska-Texas Panhandle due to the STJ. Finally, record low minimums and late season frost may also be a concern for at least the upper Great Lakes States.
Week 2 (25-31 May 2006): GSDM Stage 4 would be probable by the start of this period, possibly transitioning to GSDM Stage 1 by the end. As Gulf of Mexico moisture transport continues to improve (SSTs are above average there, ~ plus .5-1C), widespread severe local storms may become an issue for much of the central USA, particularly centered on locations such as Nebraska-Iowa on to the north and northeast. Dryline storms may become quite intense across the western High Plains. Warmth should also spread eastward from the Central and Southern Plains into the Tennessee Valley/Deep South. In fact, portions of the South may see record highs with temperatures in excess of 100F along with surface dewpoints at least into the 60s (vertical mixing may limit magnitudes). Near normal to slightly cool conditions may persist across the east and particularly for the Northeast while below normal temperatures spread across the Pacific Northwest.
Week 3 (1-7 June 2006): A transition from GSDM Stage 4-1 and possibly to Stage 2 is a concern for this period and may continue into week 4. That would mean an active southwest flow storm track pattern for the Plains as troughs come into the western states and then move northeast into the Upper Mississippi Valley. Tropical moisture transport from the Gulf of Mexico should be plentiful by this time (if not much sooner). The weather would be similar to what was observed during March, only farther north and west. A focus for severe local storms may occur from the Northern/Central Plains into the western Great Lakes States. If GSDM Stage 2 (with the tropical convection moving into the west Pacific) does evolve by, say, late week 3 into week 4, troughs digging into the central Rockies and High Plains would be more probable. That would allow the storm track to shift farther southward across the Plains, perhaps leading to a situation we saw ~May 5-9.
Specifically for southwest Kansas, the dry pattern is back (was only interrupted). Much warmer temperatures are likely starting ~ May 18, with highs well into the 90s. Starting this weekend into the following week, there may be a strong STJ to contribute to at least isolated high based thunderstorms across the elevated terrain to our west. As these storms move by, lightning and high wind may be more probable than decent rainfall; however, we will see. The main storm track will be shifted north of us, as climatology alone says. Temperatures are likely to remain well above average, with days in the 90s with even a few locations above 100F. By week 2, should GSDM Stage 1 return, that would suggest troughs coming into the Rockies and then moving northeast into the Upper Mississippi Valley. Severe local storms would likely accompany these. However, with the storm track to our north, that could mean “hot, windy and dry” at times. However, with less momentum to mix down I would think at least dryline storms and attendant rainfall would be possible (as discussed above).
Lets see if GSDM Stage 2 returns sometime during early June, as discussed above. For those really hopeful of getting decent widespread rainfall across southwest Kansas for this upcoming warm season, SSTs have been warming across the west central Pacific during the last couple of weeks. That would favor tropical convective forcing to propagate farther east, possibly favoring more persistent GSDM Stage 2 patterns.
Latest CDC Ensemble Forecast
Latest NCEP Ensemble Forecast
Additional NCEP Ensemble Output
Latest Canadian Ensemble Output
Latest Deterministic ECMWF Forecasts
http://www.cdc.noaa.gov/people/jeffrey.s.whitaker/refcst/week2/
Please see the CPC Drought Monitor for areas of dryness and the latest official outlooks and statements from Storm Prediction Center not only for severe storms, but also fire weather concerns. Finally, the CPC USA Hazards Assessment for offers additional insights not only for possible week 1 high impact weather, but week 2 as well.
I will be on quite a bit of travel through Friday, May 26. Thus I may not be able to do another writing on this Blog until Memorial Day weekend (which may be quite stormy for a good portion of the USA).
Ed Berry
Saturday, May 13, 2006
Convection Going Home
We continue to work on our next weather-climate discussion for the ESRL/PSD MJO international web site, at
http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html
The following is taken from a draft of Section 2 of these discussions called “Predictive Insights”, with some wording changes to reflect the most updated information. We hope to have our latest discussion posted this upcoming week.
SSTAs across most of the central and east equatorial Pacific are within .5 deg C of normal, with SSTs ranging from ~26C near 100W to 29C and warmer just west and southwest of the date line. SSTs of 29C and higher also extend from the southwest Pacific into the IO. At depth, anomalies around plus 1-2C extend from 50-250m east-west along the equatorial cold tongue, meaning a slightly deeper than normal oceanic thermocline. SSTAs from the IO into the west Pacific are at least plus .5-1C, with the Pacific horseshoe experiencing ~ plus 1-2C. The Caribbean into much of the NTA also has SSTAs ~plus 1-2C. Latest prediction from CPC expects ENSO-neutral conditions to prevail during the next 3-6 months (see latest TAO data here, ESRL/PSD data here). The following are links to ENSO discussions.
http://www.cdc.noaa.gov/people/klaus.wolter/MEI/
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.html
At this time the signal from the MJO is weak with the upper tropospheric divergent response moving through the WH, centered on the Atlantic Ocean. Satellite imagery (eastern hemisphere, full-disk east Pacific, full-disk west Pacific, full-disk Indian Ocean, full-disk Africa; other images available here) has enhanced convection extending from the east Pacific ITCZ across tropical South America and into especially central Africa. Tropical convection is less organized from the west Pacific toward southeast Asia (with the important exception of Typhoon Chanchu; see here). There are sporadic flare-ups across the warm South Pacific SSTs east of the date line in association with Southern Hemisphere (SH) baroclinic wave activity and associated front. Suppression continues to exist across most of the IO and has been extending eastward into most of Australia (latest 3-day averages of OLR total and anomalies here; latest 7-day average here; additional olr plots here). However, satellite imagery does show tropical convection slowly starting to increase across much of the IO during the last couple of days.
Statistical and numerical models of the MJO (see MJO forecasts, Additional MJO tools and forecasts) generally support the notion of enhanced convection returning to the Indian Ocean from tropical Africa by the start of week 2, with suppression across most of Indonesia. SSTs have also remain slightly above average across portions of the central and southern Indian Ocean (~+ 1-2C), which can be a precursor to a re-emerging MJO into the EH. Finally, SSTs also remain ~ plus 1-2C above normal across the tropical southwest Pacific, as well as the subtropical North and South Pacific and Atlantic Oceans. These basins will also contribute tropical convective forcing at times (plot of weekly global SSTAs here). The following are additional MJO monitoring tools:
http://www.cdc.noaa.gov/map/clim/olr_modes/
http://www.bom.gov.au/bmrc/clfor/cfstaff/matw/maproom/RMM/index.htm
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml
Monitoring suggests the WH will come back around into the IO from Africa in about a week, and contribute to possibly intense forcing in that region. Tropical convection may also become quite enhanced across the west Pacific during the next 1-2 weeks, with a possible consolidation ~ 120-140E during week 3. The seasonal cycle will play a role to whatever evolutionary route the tropical convective forcing takes during the next few weeks.
Since April 28th the interplay between SSTs, tropical convective forcing and circulation response-feedbacks has transitioned to a current situation best described by GSDM Stage 3. There has been an increase of zonal mean westerly flow throughout the tropical and subtropical atmospheres with anomalies ~5-10 m/s. While much of the downward and poleward propagation of these westerlies has been into the SH, some of this anomalous flow has gone through Africa into central Asia. Working with processes in the northern extratropics such as baroclinic wave packets interacting with north-south mountain ranges, these anomalous westerlies lead to an extension of the EAJ/North Pacific Jet last week. As blocking retrograded from Europe into the North Atlantic/eastern Canada (which would be expected during GSDM Stage 3), synoptic-scale storm development occurred across the central part of the country. That has led us to the blocked/split flow pattern we are currently at.
Plots of recent daily mean 150mb and 250mb vector wind anomalies clearly present a signal of twin subtropical anticylones ~40- 60W as well as the lingering pair along the date line. Subtropical cyclones are present across the IO with upper tropospheric wind anomalies ~20-30 m/s south of the equator. The North Pacific Jet remains strong for this time of year, with anomalies ~30-40 m/s. However, there has already been retraction during the last few days.
AAM anomalies were ~.5 standard deviations above the 1968-1997 climatology around May 6, and as of May 10 AAM had returned to about normal. The more up to date plot of AAM based on the operational data which uses a 1979-1998 climatology has AAM ~ 1 standard deviation below normal (see http://www.cdc.noaa.gov/map/images/aam/glaam.gif) Anomalous zonal mean westerly flow was present particularly across the SH tropical and subtropical atmospheres (seasonal cycle), and the midlatitudes (~40-60 away from the equator) of both hemispheres. Anomalous zonal mean easterly flow exists along ~30N and 30S, as well as the NH polar latitudes. The latter are actually a residual of the bursting anticylones that started in March 2006 (discussed in previous postings). Interestingly enough, there was also a weak signal of flux convergence of AAM transport into the NH midlatitudes, which may also be a residual characteristic of the recent La-Nina. Any recent signal of AAM transports was equatorward in both hemispheres as of May 10.
AAM tendency is currently negative (~ 1 standard deviation; see plot), with the frictional torque a contributor (see plot). Global mountain remains positive; however, the east Asia component is negative (Andres torque strongly positive; see plot). In the context of the GSDM, given these observations, after another week of Stage 3, Stage 4 would be most probable by the start of week 2 (next weekend), with a transition to GSDM Stage 1 during the week 3-4 time scale. Of course, timing is always unclear after roughly day 3 and predictive information statements must be expressed probabilistically to maximize skill.
For the PNA sector particularly focusing in the CONUS, the ~140-150W trough -120W ridge and eastern USA trough for the next 5 days is a good bet. Nearly all models and their ensembles have locked onto this prediction which is consistent with GSDM Stage 3 (considering the seasonal cycle). We also have to keep in mind that the current high latitude retrogression of anticyclonic circulation wind anomalies extending from the North Atlantic Ocean (leading to a negative NAO) into eastern Canada (the high-latitude AAM sink as seen from the AAM plots) will be a contributor to the weather across the CONUS not only for week 1, but afterwards.
During week 2, I would think that as the North Pacific Jet retracts and interacts with the retrograding anticyclone, a ridge across the central Pacific possibly extending well into the Arctic may be probable as week 3 approaches. That would suggest a trough to begin evolving just off the USA west coast, linking with a STJ extending into the southwest and south central states. A ridge would then probable across the central USA while a trough lingers across the east and northeast states. During the week 3-4 time-scale, an active GSDM Stage 1 pattern for particularly the northern Rockies and Plains may return (farther north than March due to seasonal transition). Most models now generally agree with this notion at least going into week 2. Experience tells us that the numerical models will likely struggle again as the tropical convective forcing comes back into the EH, particularly should a GSDM Stage 4-1 transition occur. The following is a breakdown for weeks 1-3. My confidence remains low, particularly since I have been struggling with predictions during the last few weeks.
Week 1 (14-20 May 2006): Overall, not a very active pattern for much of the USA. Roughly the eastern two-thirds of the country look to have below normal temperatures with record maximum temperatures probable for locations such as the Interior West through about the middle of this period. Starting ~ the 17th-18th very warm air should spread rapidly eastward into at least the Central and Southern Plains, with maximum temperatures in excess of 100F possible at across TX and OK. Most shower and thunderstorm activity will be east of the Mississippi River, with little precipitation to the west. Even though moisture transport from the Gulf of Mexico will be minimal, the possibility of one or two episodes of strong northwest flow thunderstorms for the Northern Plains/Upper Mississippi Valley cannot be dismissed. Finally, record low minimums and late season frost will be a concern from the northern Rockies into at least the Great Lakes States, at least early next week.
Please see the CPC Drought Monitor for areas of dryness and the latest official outlooks and statements from Storm Prediction Center not only for severe storms, but also fire weather concerns. Finally, the CPC USA Hazards Assessment for offers additional insights not only for possible week 1 high impact weather, but week 2 as well.
Week 2 (21-27 May 2006): GSDM Stage 4 would be probable by the start of this period. Rainfall chances should increase above climatology along the west coast and from the Northern Rockies into Northern Plains/Upper Mississippi Valley. The latter region may include severe local storms as Gulf of Mexico moisture transport improves (SSTs are above average there, ~ plus .5-1C). Warmth should also spread eastward across most of country, with cooler temperatures returning to the Pacific Northwest. Portions of the Southern Plains may see record highs with temperatures in excess of 100F. Lingering cool conditions are possible across the east and particularly for the Northeast.
Week 3 (28 May-3 June 2006): We would think a transition from GSDM Stage 4-1 is a concern for this period and the impacts may continue into the following week. That would mean an active southwest flow storm track pattern for the Plains as troughs come into the western states and then move northeast into the Upper Mississippi Valley. Tropical moisture transport from the Gulf of Mexico should be quite robust by this time. The weather would be similar to what was observed during March, only farther north and west. That could focus a severe local storm hazard from the Northern/Central Plains into the western Great Lakes States.
Specifically for southwest Kansas, I am afraid the dry pattern (for “whatever the reasons”) is generally back. After a cool start early this upcoming week, much warmer temperatures seem likely starting ~ May 17, with highs into the 90s. Starting next weekend into the following week, there may be a strong STJ to contribute to at least high based thunderstorms across the elevated terrain to our west. As these storms move by, lightning and high wind may be more probable than decent rainfall; however, we will see. The main storm track will be shifted north of us, as climatology alone says. Temperatures are likely to remain above average, with days in the 90s (perhaps even a few above 100F in some places). By week 3, should GSDM Stage 1 return, that would suggest troughs coming into the Rockies and then moving northeast into the Upper Mississippi Valley. Severe local storms would likely accompany these. However, with the storm track to our north, that could mean “hot, windy and dry” at times. However, with less momentum to mix down I would think at least dryline storms and attendant rainfall would be possible.
Latest CDC Ensemble Forecast
Latest NCEP Ensemble Forecast
Additional NCEP Ensemble output
Latest Canadian Ensemble Output
Latest CDC Week 2 Forecasts from the CDC Ensemble
Latest Deterministic ECMWF Forecasts
I will try to do an update on about the middle of next week.
Ed Berry
http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html
The following is taken from a draft of Section 2 of these discussions called “Predictive Insights”, with some wording changes to reflect the most updated information. We hope to have our latest discussion posted this upcoming week.
SSTAs across most of the central and east equatorial Pacific are within .5 deg C of normal, with SSTs ranging from ~26C near 100W to 29C and warmer just west and southwest of the date line. SSTs of 29C and higher also extend from the southwest Pacific into the IO. At depth, anomalies around plus 1-2C extend from 50-250m east-west along the equatorial cold tongue, meaning a slightly deeper than normal oceanic thermocline. SSTAs from the IO into the west Pacific are at least plus .5-1C, with the Pacific horseshoe experiencing ~ plus 1-2C. The Caribbean into much of the NTA also has SSTAs ~plus 1-2C. Latest prediction from CPC expects ENSO-neutral conditions to prevail during the next 3-6 months (see latest TAO data here, ESRL/PSD data here). The following are links to ENSO discussions.
http://www.cdc.noaa.gov/people/klaus.wolter/MEI/
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.html
At this time the signal from the MJO is weak with the upper tropospheric divergent response moving through the WH, centered on the Atlantic Ocean. Satellite imagery (eastern hemisphere, full-disk east Pacific, full-disk west Pacific, full-disk Indian Ocean, full-disk Africa; other images available here) has enhanced convection extending from the east Pacific ITCZ across tropical South America and into especially central Africa. Tropical convection is less organized from the west Pacific toward southeast Asia (with the important exception of Typhoon Chanchu; see here). There are sporadic flare-ups across the warm South Pacific SSTs east of the date line in association with Southern Hemisphere (SH) baroclinic wave activity and associated front. Suppression continues to exist across most of the IO and has been extending eastward into most of Australia (latest 3-day averages of OLR total and anomalies here; latest 7-day average here; additional olr plots here). However, satellite imagery does show tropical convection slowly starting to increase across much of the IO during the last couple of days.
Statistical and numerical models of the MJO (see MJO forecasts, Additional MJO tools and forecasts) generally support the notion of enhanced convection returning to the Indian Ocean from tropical Africa by the start of week 2, with suppression across most of Indonesia. SSTs have also remain slightly above average across portions of the central and southern Indian Ocean (~+ 1-2C), which can be a precursor to a re-emerging MJO into the EH. Finally, SSTs also remain ~ plus 1-2C above normal across the tropical southwest Pacific, as well as the subtropical North and South Pacific and Atlantic Oceans. These basins will also contribute tropical convective forcing at times (plot of weekly global SSTAs here). The following are additional MJO monitoring tools:
http://www.cdc.noaa.gov/map/clim/olr_modes/
http://www.bom.gov.au/bmrc/clfor/cfstaff/matw/maproom/RMM/index.htm
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml
Monitoring suggests the WH will come back around into the IO from Africa in about a week, and contribute to possibly intense forcing in that region. Tropical convection may also become quite enhanced across the west Pacific during the next 1-2 weeks, with a possible consolidation ~ 120-140E during week 3. The seasonal cycle will play a role to whatever evolutionary route the tropical convective forcing takes during the next few weeks.
Since April 28th the interplay between SSTs, tropical convective forcing and circulation response-feedbacks has transitioned to a current situation best described by GSDM Stage 3. There has been an increase of zonal mean westerly flow throughout the tropical and subtropical atmospheres with anomalies ~5-10 m/s. While much of the downward and poleward propagation of these westerlies has been into the SH, some of this anomalous flow has gone through Africa into central Asia. Working with processes in the northern extratropics such as baroclinic wave packets interacting with north-south mountain ranges, these anomalous westerlies lead to an extension of the EAJ/North Pacific Jet last week. As blocking retrograded from Europe into the North Atlantic/eastern Canada (which would be expected during GSDM Stage 3), synoptic-scale storm development occurred across the central part of the country. That has led us to the blocked/split flow pattern we are currently at.
Plots of recent daily mean 150mb and 250mb vector wind anomalies clearly present a signal of twin subtropical anticylones ~40- 60W as well as the lingering pair along the date line. Subtropical cyclones are present across the IO with upper tropospheric wind anomalies ~20-30 m/s south of the equator. The North Pacific Jet remains strong for this time of year, with anomalies ~30-40 m/s. However, there has already been retraction during the last few days.
AAM anomalies were ~.5 standard deviations above the 1968-1997 climatology around May 6, and as of May 10 AAM had returned to about normal. The more up to date plot of AAM based on the operational data which uses a 1979-1998 climatology has AAM ~ 1 standard deviation below normal (see http://www.cdc.noaa.gov/map/images/aam/glaam.gif) Anomalous zonal mean westerly flow was present particularly across the SH tropical and subtropical atmospheres (seasonal cycle), and the midlatitudes (~40-60 away from the equator) of both hemispheres. Anomalous zonal mean easterly flow exists along ~30N and 30S, as well as the NH polar latitudes. The latter are actually a residual of the bursting anticylones that started in March 2006 (discussed in previous postings). Interestingly enough, there was also a weak signal of flux convergence of AAM transport into the NH midlatitudes, which may also be a residual characteristic of the recent La-Nina. Any recent signal of AAM transports was equatorward in both hemispheres as of May 10.
AAM tendency is currently negative (~ 1 standard deviation; see plot), with the frictional torque a contributor (see plot). Global mountain remains positive; however, the east Asia component is negative (Andres torque strongly positive; see plot). In the context of the GSDM, given these observations, after another week of Stage 3, Stage 4 would be most probable by the start of week 2 (next weekend), with a transition to GSDM Stage 1 during the week 3-4 time scale. Of course, timing is always unclear after roughly day 3 and predictive information statements must be expressed probabilistically to maximize skill.
For the PNA sector particularly focusing in the CONUS, the ~140-150W trough -120W ridge and eastern USA trough for the next 5 days is a good bet. Nearly all models and their ensembles have locked onto this prediction which is consistent with GSDM Stage 3 (considering the seasonal cycle). We also have to keep in mind that the current high latitude retrogression of anticyclonic circulation wind anomalies extending from the North Atlantic Ocean (leading to a negative NAO) into eastern Canada (the high-latitude AAM sink as seen from the AAM plots) will be a contributor to the weather across the CONUS not only for week 1, but afterwards.
During week 2, I would think that as the North Pacific Jet retracts and interacts with the retrograding anticyclone, a ridge across the central Pacific possibly extending well into the Arctic may be probable as week 3 approaches. That would suggest a trough to begin evolving just off the USA west coast, linking with a STJ extending into the southwest and south central states. A ridge would then probable across the central USA while a trough lingers across the east and northeast states. During the week 3-4 time-scale, an active GSDM Stage 1 pattern for particularly the northern Rockies and Plains may return (farther north than March due to seasonal transition). Most models now generally agree with this notion at least going into week 2. Experience tells us that the numerical models will likely struggle again as the tropical convective forcing comes back into the EH, particularly should a GSDM Stage 4-1 transition occur. The following is a breakdown for weeks 1-3. My confidence remains low, particularly since I have been struggling with predictions during the last few weeks.
Week 1 (14-20 May 2006): Overall, not a very active pattern for much of the USA. Roughly the eastern two-thirds of the country look to have below normal temperatures with record maximum temperatures probable for locations such as the Interior West through about the middle of this period. Starting ~ the 17th-18th very warm air should spread rapidly eastward into at least the Central and Southern Plains, with maximum temperatures in excess of 100F possible at across TX and OK. Most shower and thunderstorm activity will be east of the Mississippi River, with little precipitation to the west. Even though moisture transport from the Gulf of Mexico will be minimal, the possibility of one or two episodes of strong northwest flow thunderstorms for the Northern Plains/Upper Mississippi Valley cannot be dismissed. Finally, record low minimums and late season frost will be a concern from the northern Rockies into at least the Great Lakes States, at least early next week.
Please see the CPC Drought Monitor for areas of dryness and the latest official outlooks and statements from Storm Prediction Center not only for severe storms, but also fire weather concerns. Finally, the CPC USA Hazards Assessment for offers additional insights not only for possible week 1 high impact weather, but week 2 as well.
Week 2 (21-27 May 2006): GSDM Stage 4 would be probable by the start of this period. Rainfall chances should increase above climatology along the west coast and from the Northern Rockies into Northern Plains/Upper Mississippi Valley. The latter region may include severe local storms as Gulf of Mexico moisture transport improves (SSTs are above average there, ~ plus .5-1C). Warmth should also spread eastward across most of country, with cooler temperatures returning to the Pacific Northwest. Portions of the Southern Plains may see record highs with temperatures in excess of 100F. Lingering cool conditions are possible across the east and particularly for the Northeast.
Week 3 (28 May-3 June 2006): We would think a transition from GSDM Stage 4-1 is a concern for this period and the impacts may continue into the following week. That would mean an active southwest flow storm track pattern for the Plains as troughs come into the western states and then move northeast into the Upper Mississippi Valley. Tropical moisture transport from the Gulf of Mexico should be quite robust by this time. The weather would be similar to what was observed during March, only farther north and west. That could focus a severe local storm hazard from the Northern/Central Plains into the western Great Lakes States.
Specifically for southwest Kansas, I am afraid the dry pattern (for “whatever the reasons”) is generally back. After a cool start early this upcoming week, much warmer temperatures seem likely starting ~ May 17, with highs into the 90s. Starting next weekend into the following week, there may be a strong STJ to contribute to at least high based thunderstorms across the elevated terrain to our west. As these storms move by, lightning and high wind may be more probable than decent rainfall; however, we will see. The main storm track will be shifted north of us, as climatology alone says. Temperatures are likely to remain above average, with days in the 90s (perhaps even a few above 100F in some places). By week 3, should GSDM Stage 1 return, that would suggest troughs coming into the Rockies and then moving northeast into the Upper Mississippi Valley. Severe local storms would likely accompany these. However, with the storm track to our north, that could mean “hot, windy and dry” at times. However, with less momentum to mix down I would think at least dryline storms and attendant rainfall would be possible.
Latest CDC Ensemble Forecast
Latest NCEP Ensemble Forecast
Additional NCEP Ensemble output
Latest Canadian Ensemble Output
Latest CDC Week 2 Forecasts from the CDC Ensemble
Latest Deterministic ECMWF Forecasts
I will try to do an update on about the middle of next week.
Ed Berry
Wednesday, May 10, 2006
Update
Since I am working on our next weather-climate discussion for the ESRL/PSD MJO web site (link below), I will not have time to post a complete writing on this blog until hopefully sometime this weekend.
http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html
A very well defined convectively coupled signal, weakly projecting onto a MJO, is currently moving across the WH. The phase speed is ~8-10 m/s, and is roughly over the tropical Atlantic Ocean (where SSTs are ~1-2C above normal). Enhanced convection with this feature extends from the east Pacific ITCZ to central Africa. Twin upper tropospheric subtropical anticyclonic circulation anomalies linked to this forcing are present ~60W. Tied to the lingering effects of La-Nina, weakly coherent tropical convective forcing remains centered ~0/150E. Typhoon Chanchu has spun off from this convection. See:
http://www.npmoc.navy.mil/jtwc.html
Convection across the IO remains strongly suppressed. However, I do feel fairly confident the WH will come back around into the EH within the next 10 days. SSTs are ~1C above normal across the IO, and it is probable that the tropical convection will increase rapidly in this region with in the next 1-2 weeks. Another consolidation ~120E is possible roughly late week 2 into week 3 (keeping in mind the seasonal cycle).
GSDM Stage 3 best describes the current weather-climate situation. The current split-flow/large amplitude pattern across North America is going to persist ~5-7 days longer than I thought last weekend. This is partly due to feedbacks from the current high-latitude retrogression of the block that started in northern Europe about a couple of weeks ago. From next weekend into week 2, GSDM Stage 4 would be probable, meaning a continued retrogression the large amplitude ridge particularly from western Canada into the central Pacific. Like the CDC and Canadian ensembles hint at, that would allow the eastern Pacific trough to reach the Pacific Northwest coast during week 2 (with a STJ into the southwest USA). A more spring-like pattern may then return to the CONUS. In summary, what I advertised last weekend for a prediction looks to be delayed perhaps a week. Oh well, I guess I am struggling.
Ed Berry
http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html
A very well defined convectively coupled signal, weakly projecting onto a MJO, is currently moving across the WH. The phase speed is ~8-10 m/s, and is roughly over the tropical Atlantic Ocean (where SSTs are ~1-2C above normal). Enhanced convection with this feature extends from the east Pacific ITCZ to central Africa. Twin upper tropospheric subtropical anticyclonic circulation anomalies linked to this forcing are present ~60W. Tied to the lingering effects of La-Nina, weakly coherent tropical convective forcing remains centered ~0/150E. Typhoon Chanchu has spun off from this convection. See:
http://www.npmoc.navy.mil/jtwc.html
Convection across the IO remains strongly suppressed. However, I do feel fairly confident the WH will come back around into the EH within the next 10 days. SSTs are ~1C above normal across the IO, and it is probable that the tropical convection will increase rapidly in this region with in the next 1-2 weeks. Another consolidation ~120E is possible roughly late week 2 into week 3 (keeping in mind the seasonal cycle).
GSDM Stage 3 best describes the current weather-climate situation. The current split-flow/large amplitude pattern across North America is going to persist ~5-7 days longer than I thought last weekend. This is partly due to feedbacks from the current high-latitude retrogression of the block that started in northern Europe about a couple of weeks ago. From next weekend into week 2, GSDM Stage 4 would be probable, meaning a continued retrogression the large amplitude ridge particularly from western Canada into the central Pacific. Like the CDC and Canadian ensembles hint at, that would allow the eastern Pacific trough to reach the Pacific Northwest coast during week 2 (with a STJ into the southwest USA). A more spring-like pattern may then return to the CONUS. In summary, what I advertised last weekend for a prediction looks to be delayed perhaps a week. Oh well, I guess I am struggling.
Ed Berry
Saturday, May 06, 2006
What Goes Around Comes Around
Global SSTs remain little changed since my posting on May 3. Across the equatorial cold tongue anomalies are ~.5C with actual SSTs varying from ~26C at 120W to 29C and warmer around the date line. In general 29C and warmer SSTs extend from the South Pacific back into the IO with pockets across the east Pacific and from the Gulf of Mexico into the tropical Atlantic Ocean. The horshoe pattern of anomalous SST warmth prevails across much of the Pacific Ocean basin, especially for the southern hemisphere. This situation projects more on a La Nina than El-Nino. The future of ENSO remains unclear, especially since we are at the so called “spring barrier of predictability”. A contribution to this so-called predictability barrier comes from the seasonal cycle. Please see the following links.
http://www.pmel.noaa.gov/tao/jsdisplay/http://www.cdc.noaa.gov/map/images/sst/sst.anom.gif
http://www.cdc.noaa.gov/map/images/sst/sst.gif
http://www.cdc.noaa.gov/people/klaus.wolter/MEI/
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.html
The discussion on the MEI was updated on May 5, and I would expect the CPC advisory to be updated within the next week.
The MJO signal (again) remains very weak. However, there have been five ~30-day relatively coherent variations of the tropical convective forcing since December 2005. These have included eastward shifts (with MJO components) from the IO across all of Indonesia, generally along the equator, before stalling. Fast convective signals then generally did propagate into the WH during these events (in concert with other complex variations of the tropical convective forcing), usually in the form of a convectively coupled Kelvin waves (Kws).
Event number five came out roughly 10-14 days ago, then stalled ~5N/150E (it may be starting to move west), while Kws (VERY loosely speaking) propagated into the WH. These Kws have excited tropical convection along both the east Pacific (with the warmer SSTs) and Atlantic ITCZs, the SPCZ, northern South America and central Africa. Some tools to monitor these tropical convective variations can be found from the following.
http://www.cdc.noaa.gov/map/clim/olr_modes/hovEa.html
http://www.ssec.wisc.edu/data/geo/mtsat/
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ir_anim_monthly.shtml
http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif
http://www.bom.gov.au/bmrc/clfor/cfstaff/matw/maproom/index.htm
The combination of the eastward shift of the EH tropical forcing and the WH signal has added a lot of westerly flow to the tropical and subtropical atmospheres during the last 2 weeks. For instance, upper tropospheric zonal mean westerly anomalies are currently ~5-10 m/s from roughly plus/minus 30 degrees of latitude of the equator.
On roughly April 24th the tendency of global relative AAM was a positive maximum of about 20 Hadleys, which signaled a transition of the global circulation to GSDM Stage 2. An observation I should have taken greater notice to is the relatively strong positive pressure torques due the Andes Mountains which may be linked to above Kws, only helping to add more westerly flow to the atmosphere. One positive Andes mountain torque occurred around April 19th and with another one currently in progress (seasonal cycle favors ~20-30 day regularity to these variations). Thus we are again seeing another positive maximum to the AAM tendency which may lead to a longer period of GSDM Stage 2-3 than I thought last week. The following are links to a few reanalysis AAM plots.
http://www.cdc.noaa.gov/map/images/reanalysis/aam_total/glaam.sig1-21.90day.gif
http://www.cdc.noaa.gov/map/images/reanalysis/aam_total/gltend.sig.90day.gif
http://www.cdc.noaa.gov/map/images/reanalysis/aam_total/gltaum.90day.gif
Cutting to the quick of all this, I do think the WH convective signal will come back around into the EH by the end of week 2 (see May 3rd posting). By that time the Andes mountain torque event should have gone though its life cycle. In addition, we cannot ever forget the East Asian topography. There already are lowering mean sea level pressures across East Asia, which may be helping to offset some of the anomalous zonal mean westerly flow present. Convection is also starting to increase across the IO, and the area from the IO into Indonesia may see intense tropical rainfall by the end of week 2.
The global circulation should mature to GSDM Stage 3 during week 1 (through next weekend), which will include retrogression of the anticyclonic circulation wind anomalies currently across northern Europe/Scandinavia. Given there are still feedbacks present from the lingering La-Nina base state, my thoughts would be for a transition to GSDM Stage 4 by the end of week 2. A signal of that would be a negative minimum of global relative AAM. During weeks 3-4 a transition to GSDM Stage 1 would be probable. After my poor assessment 4 days ago, my confidence in this evolution is low, mainly after week 1.
I think the models (please see past postings for links) look reasonable through at least the middle of next week for the CONUS. Typical of GSDM Stage 2, a trough will dig into the Rockies and Plains (with ridges off the west coast and across the Gulf of Mexico), while blocking retrogrades into Canada. The latter will enhance the split flow across North America, leading to a southward displaced storm track across the Rockies and Plains.
By next weekend into the following week, this pattern should de-amplify with the westerlies shifting north. In the presence of a STJ across the southern part of the country, by the end of week 2 into week 3, troughs may start digging along the west coast with ridging across the south central into eastern states. The blocking across Canada may shift into Alaska.
A cool and wet pattern looks like a good bet for much of the USA well into next week. Most robust cool anomalies are likely across the North and Central Plains into the Great Lakes States. Late season frosts and/or freezes may occur. Heaviest precipitation should focus from the Southern Plains into the Ohio Valley, including severe local storms. During week 2, much of the country will likely warm and dry out, perhaps very quickly. Cool and wet weather may shift back to the Pacific Northwest and perhaps linger across the Northeast. Above average heat may return to the Southern Plains by the end of this period. During week 3, perhaps finally that GSDM Stage 1 pattern for the CONUS will return. After all, I should get it right sometime!
For southwest Kansas, with our GSDM Stage 2-3 split flow pattern (with STJs), I am going to be cautiously optimistic about our rain chances well into next week. All things considered, a situation like this in July could lead to night after night of intense MCSs. Our best opportunity for rainfall should be ~Tuesday-Thursday. Temperatures look to stay below normal for about another week. Indeed, late next week at least frost could be a concern. Starting next weekend into the following week, I think temperatures will warm very quickly and rain chances will decrease. However, the STJ may still help with the rainfall opportunities.
I will try to do an update the middle of next week.
Ed Berry
http://www.pmel.noaa.gov/tao/jsdisplay/http://www.cdc.noaa.gov/map/images/sst/sst.anom.gif
http://www.cdc.noaa.gov/map/images/sst/sst.gif
http://www.cdc.noaa.gov/people/klaus.wolter/MEI/
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.html
The discussion on the MEI was updated on May 5, and I would expect the CPC advisory to be updated within the next week.
The MJO signal (again) remains very weak. However, there have been five ~30-day relatively coherent variations of the tropical convective forcing since December 2005. These have included eastward shifts (with MJO components) from the IO across all of Indonesia, generally along the equator, before stalling. Fast convective signals then generally did propagate into the WH during these events (in concert with other complex variations of the tropical convective forcing), usually in the form of a convectively coupled Kelvin waves (Kws).
Event number five came out roughly 10-14 days ago, then stalled ~5N/150E (it may be starting to move west), while Kws (VERY loosely speaking) propagated into the WH. These Kws have excited tropical convection along both the east Pacific (with the warmer SSTs) and Atlantic ITCZs, the SPCZ, northern South America and central Africa. Some tools to monitor these tropical convective variations can be found from the following.
http://www.cdc.noaa.gov/map/clim/olr_modes/hovEa.html
http://www.ssec.wisc.edu/data/geo/mtsat/
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ir_anim_monthly.shtml
http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif
http://www.bom.gov.au/bmrc/clfor/cfstaff/matw/maproom/index.htm
The combination of the eastward shift of the EH tropical forcing and the WH signal has added a lot of westerly flow to the tropical and subtropical atmospheres during the last 2 weeks. For instance, upper tropospheric zonal mean westerly anomalies are currently ~5-10 m/s from roughly plus/minus 30 degrees of latitude of the equator.
On roughly April 24th the tendency of global relative AAM was a positive maximum of about 20 Hadleys, which signaled a transition of the global circulation to GSDM Stage 2. An observation I should have taken greater notice to is the relatively strong positive pressure torques due the Andes Mountains which may be linked to above Kws, only helping to add more westerly flow to the atmosphere. One positive Andes mountain torque occurred around April 19th and with another one currently in progress (seasonal cycle favors ~20-30 day regularity to these variations). Thus we are again seeing another positive maximum to the AAM tendency which may lead to a longer period of GSDM Stage 2-3 than I thought last week. The following are links to a few reanalysis AAM plots.
http://www.cdc.noaa.gov/map/images/reanalysis/aam_total/glaam.sig1-21.90day.gif
http://www.cdc.noaa.gov/map/images/reanalysis/aam_total/gltend.sig.90day.gif
http://www.cdc.noaa.gov/map/images/reanalysis/aam_total/gltaum.90day.gif
Cutting to the quick of all this, I do think the WH convective signal will come back around into the EH by the end of week 2 (see May 3rd posting). By that time the Andes mountain torque event should have gone though its life cycle. In addition, we cannot ever forget the East Asian topography. There already are lowering mean sea level pressures across East Asia, which may be helping to offset some of the anomalous zonal mean westerly flow present. Convection is also starting to increase across the IO, and the area from the IO into Indonesia may see intense tropical rainfall by the end of week 2.
The global circulation should mature to GSDM Stage 3 during week 1 (through next weekend), which will include retrogression of the anticyclonic circulation wind anomalies currently across northern Europe/Scandinavia. Given there are still feedbacks present from the lingering La-Nina base state, my thoughts would be for a transition to GSDM Stage 4 by the end of week 2. A signal of that would be a negative minimum of global relative AAM. During weeks 3-4 a transition to GSDM Stage 1 would be probable. After my poor assessment 4 days ago, my confidence in this evolution is low, mainly after week 1.
I think the models (please see past postings for links) look reasonable through at least the middle of next week for the CONUS. Typical of GSDM Stage 2, a trough will dig into the Rockies and Plains (with ridges off the west coast and across the Gulf of Mexico), while blocking retrogrades into Canada. The latter will enhance the split flow across North America, leading to a southward displaced storm track across the Rockies and Plains.
By next weekend into the following week, this pattern should de-amplify with the westerlies shifting north. In the presence of a STJ across the southern part of the country, by the end of week 2 into week 3, troughs may start digging along the west coast with ridging across the south central into eastern states. The blocking across Canada may shift into Alaska.
A cool and wet pattern looks like a good bet for much of the USA well into next week. Most robust cool anomalies are likely across the North and Central Plains into the Great Lakes States. Late season frosts and/or freezes may occur. Heaviest precipitation should focus from the Southern Plains into the Ohio Valley, including severe local storms. During week 2, much of the country will likely warm and dry out, perhaps very quickly. Cool and wet weather may shift back to the Pacific Northwest and perhaps linger across the Northeast. Above average heat may return to the Southern Plains by the end of this period. During week 3, perhaps finally that GSDM Stage 1 pattern for the CONUS will return. After all, I should get it right sometime!
For southwest Kansas, with our GSDM Stage 2-3 split flow pattern (with STJs), I am going to be cautiously optimistic about our rain chances well into next week. All things considered, a situation like this in July could lead to night after night of intense MCSs. Our best opportunity for rainfall should be ~Tuesday-Thursday. Temperatures look to stay below normal for about another week. Indeed, late next week at least frost could be a concern. Starting next weekend into the following week, I think temperatures will warm very quickly and rain chances will decrease. However, the STJ may still help with the rainfall opportunities.
I will try to do an update the middle of next week.
Ed Berry
Wednesday, May 03, 2006
Where Will the Westerly Anomalies Go?
Tropical Pacific SSTs have changed little since my last posting on April 29th. Anomalies along the equatorial cold tongue are generally within .5C of normal with weak cool conditions across the east Pacific and warmth across the date line region. Actual temperatures vary from ~26C near 120W to at least 29C southwest of the date line. The 29C and warmer SSTs (useful threshold for maintaining deep moist convection) generally extend from the IO into the South Pacific and have also recently appeared just south of Mexico (along the ITCZ). At depth there is some warmth of ~plus 0.5-1.5C down to about 200m around the date line, which suggests a slightly deeper than normal ocean thermocline. The horseshoe pattern of anomalous warmth still prevails across the subtropics and lower midlatitudes of the Pacific Ocean, as well as across much of the northern tropical Atlantic. Details can be found from the following links.
http://www.pmel.noaa.gov/tao/jsdisplay/
http://www.cdc.noaa.gov/map/clim/sst.shtml
http://www.nhc.noaa.gov/aboutsst.shtml
The ENSO situation remains unclear. However, there are monitoring tools which suggest the effects of La-Nina are still lingering. The following discussions should be updated within the next week or so to provide additional information.
http://www.cdc.noaa.gov/people/klaus.wolter/MEI/
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.html
Any MJO signal is still very weak. During roughly the last 10 days an eastward shift of the tropical convective forcing occurred (see April 29th posting), linked to a convectively coupled Kelvin wave (Kw). At this time the centroid of the tropical forcing is at about 5N/150E, and extended from central Indonesia into the west Pacific. Monitoring suggests this enhanced region of tropical rainfall has stalled. Additionally, enhanced rainfall was increasing across both northern South America and central Africa, with strong flare-ups across both the South Pacific (interacting with fronts) and even the eastern Pacific ITCZ.
The point is while the most significant tropical forcing still remains in the EH, there is a signal currently propagating through the WH tied to the Kw. My feeling is that the strongest forcing will remain across the EH, while the propagating signal comes back around into the regions of Africa and the IO during the next 2 weeks. I would expect to see perhaps a rapid enhancement of the IO convection within the next week or so, with possibly the Indonesian rainfall shifting back to the west. Similar to at least 5 previous events going back to December 2005, another consolidation of the tropical convection may occur late week 2 or 3. Please see the following links for details (as well as additional navigation to relevant links).
http://www.cdc.noaa.gov/map/clim/olr_modes/
http://www.bom.gov.au/bmrc/clfor/cfstaff/matw/maproom/index.htm
http://www.ssec.wisc.edu/data/geo/mtsat/
http://trmm.gsfc.nasa.gov/
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ir_anim_monthly.shtml
GSDM Stage 3 best describes the circulation response to the tropical convective forcing (in addition to other processes). Global relative AAM is still about a half a standard deviation below the 1968-1997 reanalysis data climatology. However, this is an increase from about minus 2 standard deviations from 2 weeks ago (see links below), and I think we are seeing GSDM Stage 3 in the presence of a weak La-Nina base state. Importantly, deep zonal mean anomalous westerly flow of at least 5m/s extends throughout the equatorial and subtropical atmospheres, and downward and poleward movement of these anomalies would be probable. An important question for prediction is just how much are these enhanced zonal mean westerlies going to impact character of the global circulation? Related questions also concern the impact of the both the tropical convective as well as topographic forcing interacting with RWDs within the enhanced westerly flow. These RWDs will be crucial for the synoptic evolution of midlatitude troughs and ridges.
http://www.cdc.noaa.gov/map/images/reanalysis/aam_total/glaam.sig1-21.90day.gif
http://www.cdc.noaa.gov/map/clim/aam.rean.shtml
http://www.cdc.noaa.gov/map/clim/aam.shtml
My own feeling is to continue the thoughts offered on the April 29th writing. The enhanced mid/upper tropospheric westerlies are coming back around through north Africa and are headed toward subtropical Asia. Interacting with the Indonesian tropical convection, an extension of the polar jetstream (East Asian Jet (EAJ)) across the North Pacific ~40-50N is probable. This will be displaced a bit north of what is expected during these kind of situations due to the weak La-Nina base state. Meanwhile, a blocking anticyclone located in the Eurasian sector is probable to retrograde into Canada by the end of week 2. There is a tendency to see retrogression of existing high latitude anticyclonic circulation anomalies from Eurasia into North America during GSDM Stage 3 situations (complicated feedback issues). Starting sometime next week a well defined split flow pattern across North America looks plausible.
Focusing on the CONUS, where will be the most probable location of cyclonic circulation anomalies as the blocking anticyclone retrogrades through Canada? There have been differences in the numerical models (including large ensemble spreads) on resolving this matter. With the tropical forcing remaining well in the EH, I would expect to see closed lows developing across the Rockies and then lifting northeast into the Upper Mississippi Valley. More generally, much of the country may have a southward displaced storm track (regionally due to the Canada blocking; not to be confused with a northward displaced storm track in the zonal mean). With this pattern locations from the Pacific Northwest into the Rockies and Plains may experience the most active weather, including severe storms across the central part of the country. In terms of above average rainfall locations from the Upper Mississippi Valley all the way to possibly even the Mid-Atlantic States may be in line. Portions of the Southern High Plains look to remain dryer than normal.
I think this “GSDM La-Nina springtime version of Stage 3” will mature during week 2, possibly quickly transitioning to GSDM Stage 1 by the end of week 3 (~May 24th). At least for weeks 1 and 2, I do like the solutions offered by the CDC ensemble and ECMWF deterministic run (see links). However, all numerical models are generally starting to converge.
http://www.cdc.noaa.gov/map/images/ens_jsw/ens_jsw.html
http://www.cdc.noaa.gov/people/jeffrey.s.whitaker/refcst/week2/
http://www.ecmwf.int/
For Southwest Kansas, I wish I could offer more optimism for the decent periods of widespread rainfall that most would like to see. I hope that respectable rainfall occurs between now and this weekend. Opportunities for some showers and storms (perhaps linked to the dryline) should exist during the next couple of weeks, particularly with enhanced episodes of the STJ linked to flare-ups across both the South Pacific and eastern Pacific ITCZ. However, above average westerly flow coming across the Rockies starting next week is not at all favorable for repeated widespread rainfall events across southwest Kansas. In addition, should we start to see individual synoptic lows lift northeast toward locations such as Iowa from the Rockies, a couple of days of “hot southwest winds and some blowing dust” is not out of the question. If I were doing a week 2 prediction, it would read “above normal temperatures and below normal precipitation”. Should the circulation transition back to GSDM Stage 1 after this period, that may shift the storm track farther north (which may also not be good for decent rainfall).
For those interested on learning more about our GSDM, the Weickmann and Berry (2006) paper, “A synoptic-dynamic model of subseasonal atmospheric variability”, has just been formally accepted for publication into Monthly Weather Review (MWR). I will try to provide a link to a soft copy of our paper in a future posting on this web site.
I will try to do an update this weekend. We are working on another weather-climate discussion for the PSD MJO web page, which we hope to post within the next week or so (http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html ).
Ed Berry
http://www.pmel.noaa.gov/tao/jsdisplay/
http://www.cdc.noaa.gov/map/clim/sst.shtml
http://www.nhc.noaa.gov/aboutsst.shtml
The ENSO situation remains unclear. However, there are monitoring tools which suggest the effects of La-Nina are still lingering. The following discussions should be updated within the next week or so to provide additional information.
http://www.cdc.noaa.gov/people/klaus.wolter/MEI/
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.html
Any MJO signal is still very weak. During roughly the last 10 days an eastward shift of the tropical convective forcing occurred (see April 29th posting), linked to a convectively coupled Kelvin wave (Kw). At this time the centroid of the tropical forcing is at about 5N/150E, and extended from central Indonesia into the west Pacific. Monitoring suggests this enhanced region of tropical rainfall has stalled. Additionally, enhanced rainfall was increasing across both northern South America and central Africa, with strong flare-ups across both the South Pacific (interacting with fronts) and even the eastern Pacific ITCZ.
The point is while the most significant tropical forcing still remains in the EH, there is a signal currently propagating through the WH tied to the Kw. My feeling is that the strongest forcing will remain across the EH, while the propagating signal comes back around into the regions of Africa and the IO during the next 2 weeks. I would expect to see perhaps a rapid enhancement of the IO convection within the next week or so, with possibly the Indonesian rainfall shifting back to the west. Similar to at least 5 previous events going back to December 2005, another consolidation of the tropical convection may occur late week 2 or 3. Please see the following links for details (as well as additional navigation to relevant links).
http://www.cdc.noaa.gov/map/clim/olr_modes/
http://www.bom.gov.au/bmrc/clfor/cfstaff/matw/maproom/index.htm
http://www.ssec.wisc.edu/data/geo/mtsat/
http://trmm.gsfc.nasa.gov/
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ir_anim_monthly.shtml
GSDM Stage 3 best describes the circulation response to the tropical convective forcing (in addition to other processes). Global relative AAM is still about a half a standard deviation below the 1968-1997 reanalysis data climatology. However, this is an increase from about minus 2 standard deviations from 2 weeks ago (see links below), and I think we are seeing GSDM Stage 3 in the presence of a weak La-Nina base state. Importantly, deep zonal mean anomalous westerly flow of at least 5m/s extends throughout the equatorial and subtropical atmospheres, and downward and poleward movement of these anomalies would be probable. An important question for prediction is just how much are these enhanced zonal mean westerlies going to impact character of the global circulation? Related questions also concern the impact of the both the tropical convective as well as topographic forcing interacting with RWDs within the enhanced westerly flow. These RWDs will be crucial for the synoptic evolution of midlatitude troughs and ridges.
http://www.cdc.noaa.gov/map/images/reanalysis/aam_total/glaam.sig1-21.90day.gif
http://www.cdc.noaa.gov/map/clim/aam.rean.shtml
http://www.cdc.noaa.gov/map/clim/aam.shtml
My own feeling is to continue the thoughts offered on the April 29th writing. The enhanced mid/upper tropospheric westerlies are coming back around through north Africa and are headed toward subtropical Asia. Interacting with the Indonesian tropical convection, an extension of the polar jetstream (East Asian Jet (EAJ)) across the North Pacific ~40-50N is probable. This will be displaced a bit north of what is expected during these kind of situations due to the weak La-Nina base state. Meanwhile, a blocking anticyclone located in the Eurasian sector is probable to retrograde into Canada by the end of week 2. There is a tendency to see retrogression of existing high latitude anticyclonic circulation anomalies from Eurasia into North America during GSDM Stage 3 situations (complicated feedback issues). Starting sometime next week a well defined split flow pattern across North America looks plausible.
Focusing on the CONUS, where will be the most probable location of cyclonic circulation anomalies as the blocking anticyclone retrogrades through Canada? There have been differences in the numerical models (including large ensemble spreads) on resolving this matter. With the tropical forcing remaining well in the EH, I would expect to see closed lows developing across the Rockies and then lifting northeast into the Upper Mississippi Valley. More generally, much of the country may have a southward displaced storm track (regionally due to the Canada blocking; not to be confused with a northward displaced storm track in the zonal mean). With this pattern locations from the Pacific Northwest into the Rockies and Plains may experience the most active weather, including severe storms across the central part of the country. In terms of above average rainfall locations from the Upper Mississippi Valley all the way to possibly even the Mid-Atlantic States may be in line. Portions of the Southern High Plains look to remain dryer than normal.
I think this “GSDM La-Nina springtime version of Stage 3” will mature during week 2, possibly quickly transitioning to GSDM Stage 1 by the end of week 3 (~May 24th). At least for weeks 1 and 2, I do like the solutions offered by the CDC ensemble and ECMWF deterministic run (see links). However, all numerical models are generally starting to converge.
http://www.cdc.noaa.gov/map/images/ens_jsw/ens_jsw.html
http://www.cdc.noaa.gov/people/jeffrey.s.whitaker/refcst/week2/
http://www.ecmwf.int/
For Southwest Kansas, I wish I could offer more optimism for the decent periods of widespread rainfall that most would like to see. I hope that respectable rainfall occurs between now and this weekend. Opportunities for some showers and storms (perhaps linked to the dryline) should exist during the next couple of weeks, particularly with enhanced episodes of the STJ linked to flare-ups across both the South Pacific and eastern Pacific ITCZ. However, above average westerly flow coming across the Rockies starting next week is not at all favorable for repeated widespread rainfall events across southwest Kansas. In addition, should we start to see individual synoptic lows lift northeast toward locations such as Iowa from the Rockies, a couple of days of “hot southwest winds and some blowing dust” is not out of the question. If I were doing a week 2 prediction, it would read “above normal temperatures and below normal precipitation”. Should the circulation transition back to GSDM Stage 1 after this period, that may shift the storm track farther north (which may also not be good for decent rainfall).
For those interested on learning more about our GSDM, the Weickmann and Berry (2006) paper, “A synoptic-dynamic model of subseasonal atmospheric variability”, has just been formally accepted for publication into Monthly Weather Review (MWR). I will try to provide a link to a soft copy of our paper in a future posting on this web site.
I will try to do an update this weekend. We are working on another weather-climate discussion for the PSD MJO web page, which we hope to post within the next week or so (http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html ).
Ed Berry
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