Atmospheric Insights: June 2006

Wednesday, June 28, 2006

Down in Flames!!!

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

The gist is that from taking into consideration the interactions of 4 different subseasonal time scales, a sequence depicting a coherent set of repeatable events has been derived for the Northern Hemisphere cold season from November-March. 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. Ideally it would be advantageous to post our weather-climate discussions (link at the bottom) with greater frequency to provide additional detail while having a more complete weather-climate record of attribution and prediction. In these discussions I adapt the GSDM for the warm season. Our list of work includes a seasonally adjusted rendition of the GSDM.

An equatorial trade wind surge of ~5-10 m/s led to some cooling of central and east Pacific SSTs during the past week. However anomalies remain slightly above normal west of 120W with ~plus 1-2C warmth down to roughly 200m at the date line. Meanwhile, also during the past week roughly 0.5-1C SST cooling was also observed across the equatorial Indian Ocean. The latter was the result of enhanced rainfall in that region. Still, above average SSTs dominate the global tropics with actual temperatures in excess of 29C from the South Pacific into the Indian Ocean. Additional global SST information can be obtained from latest TAO data here, ESRL/PSD data here, and CPC data

http://www.cpc.ncep.noaa.gov/products/predictions/threats/index_gloss.html.

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

While monsoon enhanced convection continues from Indian Ocean into Southeast Asia, a well defined separate region of tropical convective forcing is moving into the western Pacific as I type. Per satellite imagery and monitoring tools such as Hovmoller plots of OLR and their anomalies, this separate area was centered ~ 0/160E (OLRA ~ minus 70-90 W/m**2), and extended from around the date line to eastern Indonesia. The latter region of tropical forcing projects strongly onto a convectively coupled Kelvin wave, per coherent modes Hovmollers. My own loose phase speed calculations have this Kelvin wave moving east at about 10-12 m/s (~8-9 deg of longitude/day), and will be well into the Western Hemisphere by the end of week 1.

A week ago I was expecting a consolidation of both SST boundary and dynamically forced tropical convection, with a possible MJO to develop from this occurrence. There was a brief consolidation ~ 10N/110E a few days ago. However, as we have seen since about mid April, convectively coupled Kelvin waves have been the dominate mode of tropical convective forcing, and that behavior appears to be continuing per above. I did not reflect this possibility very well with my predictive input; and once again, this emphasizes both the importance of daily weather-climate monitoring and forecast uncertainty. Recent week-two NCEP model performance has also been problematic, likely related to the complexity discussed above (see http://www.cpc.ncep.noaa.gov/schemm/z500ac_wk2_na.html , for example).

Whatever I can offer for predictive insight will be made with very low confidence at this point. My feeling is to go with the continuation of convectively coupled Kelvin waves dominating the dynamic signal for tropical forcing while SST boundary forced and monsoon system convection persists from generally Southeast Asia into India. If it stays coherent, the dynamic signal should be around 90W by about the middle of week 2 then moving back into the Eastern Hemisphere after week 3.

Empirical, statistical and numerical prediction tools are inconclusive for useful information about the future evolution of the tropical convection. Please see ESRL/PSD MJO tools , BMRC MJO tools, CPC MJO tools, and http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/index.primjo.html for the details (and draw your own conclusions).

Zonal mean 200mb easterly wind anomalies of ~5-15 m/s continue to propagate into the midlatitude atmospheres of both hemispheres, being replaced with zonal mean westerly anomalies throughout the tropical and subtropical atmospheres. These westerly anomalies were strongest at about 15N, ~15 m/s. Animations of 150mb and 250mb daily mean vector wind anomalies show these westerlies were linked with the divergent outflow from the Indian Ocean tropical convective flare-up which occurred around June 17th. From about June 22-24th, these westerlies were quite expansive across the tropical and subtropical Western Hemisphere (AAM tendency was strongly positive), with easterly wind anomalies from the Indian Ocean into Africa. In fact, the Wheeler Index (EOFs understood) showed a slightly greater than 1 standard deviation MJO projection at that time. This was around the time the tropical forcing was consolidating. A fast Rossby wave energy dispersion tied to the forcing led to the retrogression of the western USA ridge, and also contributed to the excessive rainfall along the East Coast. This dispersion is currently propagating into the Atlantic, easing the heavy rain hazard there. These interactions led to the transition of the global circulation to GSDM Stage 2.

As already discussed, just when it appeared a nice scenario of coherent tropical convective forcing, circulation response and feedbacks was evolving (particularly with the warm SSTs), we saw nothing more than a transient event linked to the Kelvin wave. Equatorial upper tropospheric westerlies remain robust from the central Pacific into the Atlantic while a separate region of enhanced westerlies persists across the subtropical date line region. The dynamic forcing for the latter region of anomalous westerly flow is unclear (one can always speculate); however, these winds appear directed toward the western USA. Finally, whether or not another oceanic Kelvin wave occurs should the low level westerlies (currently across the Indian Ocean into Indonesia) head into the equatorial date line region remains to be seen.

Tropospheric relative AAM continues to increase and is about 1 standard deviation below the 1968-1997 reanalysis data climatology, which lags 3 days from the current time. The operational data plot shows AAM has ~ 2 standard deviations below the 1979-1998 climatology (see http://www.cdc.noaa.gov/map/images/aam/glaam.gif). With contributions still coming from the mountain and frictional torques, the AAM tendency remains positive (links below), but less than its maximum a few days ago.

Within the framework of the GSDM I think we are still in a summertime rendition of GSDM Stage 2 (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 budget plots, including tendency). Where we go from here is about as uncertain as it gets (not all that “unusual” for boreal summer). We already know there are at least 2 regions of tropical convective forcing (discussed above), and other warm ocean basins such as the North Tropical Atlantic may also have an impact (and not just from the current Kelvin wave). Very loosely I would think a transition to a summertime version of GSDM Stage 3 during week 1 into week 2 is most probable. Afterwards, uncertainty is too high to offer anything useful.

Week 1 (29 June -5 July 2006): I think there will be more westerly flow coming into the western USA, suggesting a deamplification and downstream progression of the current western CONUS ridge. Most models are trending toward this solution. This should allow some tropical moisture transport from the Gulf of Mexico into the central states during this period (due to at least weak lee-side Rocky Mountain troughs). The East Coast should get a respite from the very heavy rainfall and the Southwest USA monsoon is likely to remain suppressed. Broadly, synoptically we may observe split flow along or just off the North American West Coast (with a ridge in Alaska) and confluent flow across the eastern half of the country. Intense heat may start to build across portions of the Southern and Central Plains.

Active and possibly severe MCSs/Derechoes (along with areas of heavy rainfall) from the Northern and Central Plains into the Great Lakes and Ohio Valley will be a concern as moisture transport improves. Increasing upper tropospheric anomalous westerly flow across the Tropical North Atlantic may lead to an unfavorable environment for tropical cyclogenesis in that region. Please see http://www.nhc.noaa.gov/ for the latest tropical cyclone information.

Week 2 (06–12 July 2006): This is the period when the dynamic tropical convective signal may become robust across the Western Hemisphere. While I can type many scenarios and anyone can take their pick, it is too unclear to offer a predictive solution that is useful, including having a “decent” probability of occurring.

Week 3 (13-19 July 2006): Same as week 2. However, should a dynamic tropical forcing signal (the Kelvin wave) propagate through the Western Hemisphere like we observed during late May and early June, tropical cyclogenesis may be a concern for both the east Pacific and Tropical North Atlantic Oceans.

My last outlook for Southwest Kansas issued a week ago is going down in flames. There is likely to be a synoptic-scale boundary across the Plains that will eventually act as a focus for thunderstorm development, especially as moisture transport from the Gulf of Mexico improves, during week 1. Much of that MCS activity may stay west (linked to the higher terrain) and north/northeast of us as we remain in the warm air (with near-above normal temperatures). However, I would think there should be one or two rounds of storms during the upcoming Independence Day weekend. Afterwards, I am going to leave it unclear.

The time -filtered coherent modes Hovmoller plots of OLR and OLRA are at
http://www.cdc.noaa.gov/map/clim/olr_modes/), velocity potential Hovmollers at http://www.cpc.ncep.noaa.gov/products/intraseasonal/vpot_tlon.html , and an animation of velocity potential overlayed on OLRAs are at http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ir_anim_monthly.shtml.

Satellite imagery and other information can be found from the following links: eastern hemisphere, full-disk west Pacific, mtsat, IO, Africa, http://www.jma.go.jp/en/gms/ ; other imagery here. Latest tropical cyclone statements can be found from http://www.nhc.noaa.gov/, while the latest 3-day averages of OLR totals and anomalies and other data can be found here
http://www.cdc.noaa.gov/map/clim/glbcir.anim.shtml (animations of various fields from the operational data)

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml (Global Tropical Hazards Assessment available from this site, along with other useful information)

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/

http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html (link to our Weather-Climate discussions)

Please see the CPC Drought Monitor for areas of dryness and the latest official outlooks and statements from the 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 this upcoming weekend.
Ed Berry

Sunday, June 25, 2006

The Tune Continues

Thursday, June 22, 2006

Playing a Different Tune

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

The gist is that from taking into consideration the interactions of 4 different subseasonal time scales, a sequence depicting a coherent set of repeatable events has been derived for the Northern Hemisphere cold season from November-March. 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. Ideally it would be advantageous to post our weather-climate discussions (link at the bottom) with greater frequency to provide additional detail while having a more complete weather-climate record of attribution and prediction. In these discussions I adapt the GSDM for the warm season. Our list of work includes a seasonally adjusted rendition of the GSDM.

SSTs have changed little since my last posting on June 17th. Global SST information can be obtained from latest TAO data here, ESRL/PSD data here, and CPC data

http://www.cpc.ncep.noaa.gov/products/predictions/threats/index_gloss.html.

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

Linked to the convectively coupled Kelvin wave that moved from the Western into the Eastern hemisphere a couple of weeks ago, tropical convective forcing has significantly increased across the Indian Ocean (IO) during the last 5-7 days. Per satellite imagery the centroid was at ~5N/90E, and may the largest positive anomalies of tropical forcing observed in that area for at least a year. With widespread negative anomalies of outgoing longwave radiation (OLR) ~minus 70-90 W/m**2 and lower, this region of convection extended from the equatorial IO and Arabian Sea through the Bay of Bengal and western Indonesia and finally into Southeast Asia. A much less intense region of tropical convection was located across the West Pacific, centered at roughly 10N/145E. The latter region was the most dominate until about a week ago.

My thoughts are a true MJO may be developing out of the IO convection, understanding the role of the monsoon systems and seasonal cycle (which does not favor MJOs this time of year). We may be starting to get a SST, tropical convective forcing and global circulation response feedback process going. If this is the case, there will be seasonal forecast implications; for example, the development of a warm event across the central and eastern equatorial Pacific (a.k.a. El-Nino) may become a possibility.

In my last posting I favored a consolidation of the two above mentioned areas of tropical convection, with the West Pacific being the stronger. Instead, the IO convection is taking over, and I may still get my consolidation with a different evolution. Linear (and obvious) thinking would have suggested the latter; that is, going with the dynamical signal instead of the boundary forcing (which my research colleague did favor – the lead author on our paper). So, I am going to play the tune of the IO convection expanding eastward and “absorb” the convection farther east, while propagating east and north as possibly a MJO. By the end of week 2, we may see a spatially tilted structure of tropical convective forcing extending from roughly India east and southeast across Indonesia into the West Pacific, centered ~5-10N/110-120E. How far east this all propagates is a very good question.

A few of the empirical/statistical tools and numerical models support the above; for example, the empirical extrapolated predictions from the time-filtered coherent modes technique and even the NCEP GFS model. However, they are generally inconclusive. Please see ESRL/PSD MJO tools , BMRC MJO tools, CPC MJO tools, and

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/index.primjo.html

for the details.

Zonal mean 200mb wind anomalies of ~ minus 10-20 m/s continue to propagate into the subtropical and lower midlatitude atmospheres of both hemispheres, with zonal mean westerly anomalies ~5-10m/s appearing along and just north of the equator. These poleward propagating zonal mean easterly anomalies will favor stronger than normal subtropical ridges across both hemispheres for at least the next couple of weeks. Strong zonal mean westerly wind anomalies (~15-30 m/s; largest in the Southern Hemisphere) still prevail across the Northern and Southern hemisphere extratropics, indicative of inter-hemispheric symmetry due to tropical forcing.

AAM anomalies (largest across the Southern Hemisphere) still remain ~ minus 2 standard deviations below the 1968-1997 climatology, based on the reanalysis data which lags 3 days from the current time. The operational data plot shows AAM has ~ 3 standard deviations below the 1979-1998 climatology (see http://www.cdc.noaa.gov/map/images/aam/glaam.gif). With contributions coming from particularly the frictional torque and even the Earth component of the budget, the AAM tendency has been positive (links below).

Animations of daily mean 150mb and 250mb vector wind anomalies show that a strong signal of anomalous divergence due to the convection has appeared across the Arabian Sea and much of the IO during the last 3-5 days. Loosely, there are twin subtropical anticyclones in that region (with twin low level cyclones and surface westerlies on the equator – baroclinic mode). About 7-10 days ago twin anticyclones were located across the west Pacific, in response to the tropical SST boundary forced convection. Interacting with the baroclinic wave packets moving through Asia (one of the fast components of the GSDM), there is already a phase reversal of circulation anomalies starting to appear across the extratropical North Pacific ~ 45N/180. About a week ago there was a cyclonic circulation anomaly in that area. In the last few days an anticyclonic circulation anomaly has now appeared there. This is all directly linked to Rossby wave energy dispersion emanating from the IO convection as well as the poleward propagating zonal mean easterly anomalies (discussed above).

Equatorial westerly wind anomalies are becoming more robust globally, with their zonal mean anomalies ~ 5-10 m/s at 200mb. I would like to argue these westerly anomalies are appearing as the result of wave breaking of extratropical baroclinic wave trains/packets interacting with the eastern hemisphere (first the West Pacific, now Indian Ocean) tropical convective forcing, leading to “expected AAM fluxes”. Indeed, there is now a zonal mean momentum sink at ~30N with flux convergence ~ 45N. However, that is an outstanding research issue, and needs attention for both theoretical and prediction concerns. In any case, the appearance of these upper tropospheric equatorial westerly wind anomalies is another one of the components leading to the observed positive tendency in global relative AAM. In very general terms, I would expect the equatorial westerly wind anomalies and AAM to continue increasing during the next couple of weeks particularly if a MJO does evolve.

Within the framework of the GSDM I think we are transitioning to a summertime rendition of GSDM Stage 2, particularly since the frictional torque is positive while the global mountain torque is trending toward positive (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 budget plots, including tendency). The phase reversal of circulation anomalies across the extratropical North Pacific and increasing equatorial westerlies also support that notion. My thought is that the tropical West and Northwest Pacific convection started this change, and now the very intense convection evolving into perhaps a MJO across the central IO may continue this process.

During August of 2004 and 2005 we observed summertime versions of GSDM Stage 2, and that response was a “prolific” heavy rain and severe local storms producer for the middle of the country (along with cooler than normal temperatures). Please see our past weather-climate discussions for details. Given the recent SST behaviors and possible development of a MJO out of the IO convection, perhaps the GSDM Stage 2 response may persist for a few weeks. In the outlooks that follow, while I feel comfortable about transitioning to GSDM Stage 2, my confidence in the synoptic evolution is very low given the appearance of the extremely intense IO convection and its future. As discussed below, whatever the details area, we should see a west and northward shift of the current circulation structure across the Asia-Pacific-North American sector.

Week 1 (23-29 June 2006): Tropical moisture transport from the deep tropics through the Gulf of Mexico into the eastern half of the CONUS is well established. A transition to GSDM Stage 2 is most probable, meaning ridge development from the eastern Pacific into the Alaska with a downstream trough across western Canada and the Pacific Northwest/Northern Rockies by the end of this period. A belt of strong cyclonic westerly flow along and south of the USA/Canada border from perhaps the Pacific Northwest/Northern Rockies topping a ridge extending from the Atlantic into the eastern and southeastern USA would then be expected. Finally, I would also expect a ridge across Desert Southwest, with a cyclonic shear axis/trough in between the two intense subtropical highs. The above described evolution may appear as a slow retrogression and amplification from the current synoptic regime (and anomalies) across the PNA sector. Latest available numerical models indicate an improving trend toward this week 1 prediction (see links below).

Active and possibly severe MCSs/Derechoes (along with areas of heavy rainfall) from the Northern and Central Rockies to most of the Plains and Central states into the Great Lakes and Ohio Valley will be a concern. Additionally, locations from southeast Texas too much of the East Coast may receive locally excessive rainfall. Finally, with the zonal mean anomalous easterly flow propagating into the midlatitudes, that environment would be more favorable for active easterly waves across the Tropical North Atlantic which could undergo tropical cyclogenesis. Please see http://www.nhc.noaa.gov/ for the latest tropical cyclone information.

Week 2 (30 June-06 July 2006): GSDM Stage 2 persisting is probable, with Hazards similar to week 1. In this situation areas for excessive heat and humidity may be confined to the Deep South but with synoptic northward excursions. The Desert Southwest monsoon may remain suppressed due to the Pacific Northwest trough.

Week 3 (07-13 July 2006): GSDM Stage 2, possibly transitioning to Stage 3 (need to leave this possibility open), would be my best offering. Should we see Stage 3, it is probable the Upper Mississippi Valley and Great Lakes would have below normal temperatures with warmth across the Pacific Northwest and Inter-Mountain West. Roughly the eastern half of the country would be wet.

Loosely, Southwest Kansas may see several rounds of MCSs/clusters of thunderstorms for at least the next couple of weeks. Temperatures should average out near normal. Maximum temperatures may vary from around 100F on the dry days to upper 60s and 70s during post frontal/MCS days. Hopefully this situation will persist into week 3 given the past extended period of dryness. This outlook and all the discussion above only support my following assertion, already stated in past postings. I do not think our weather-climate situation supports an extended period of tremendously excessive scorching apocalyptic heat with no rainfall, for at least the next month (and maybe the rest of this summer).

The time -filtered coherent modes Hovmoller plots of OLR and OLRA are at http://www.cdc.noaa.gov/map/clim/olr_modes/), velocity potential Hovmollers at http://www.cpc.ncep.noaa.gov/products/intraseasonal/vpot_tlon.html , and an animation of velocity potential overlayed on OLRAs are at http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ir_anim_monthly.shtml.

Satellite imagery and other information can be found from the following links: eastern hemisphere, full-disk west Pacific, mtsat, IO, Africa, http://www.jma.go.jp/en/gms/ ; other imagery here. Latest tropical cyclone statements can be found from http://www.nhc.noaa.gov/, while the latest 3-day averages of OLR totals and anomalies and other data can be found here

http://www.cdc.noaa.gov/map/clim/glbcir.anim.shtml (animations of various fields from the operational data)

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml (Global Tropical Hazards Assessment available from this site, along with other useful information)

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/

http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html (link to our Weather-Climate discussions)

Please see the CPC Drought Monitor for areas of dryness and the latest official outlooks and statements from the 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 this upcoming weekend.
Ed Berry

Saturday, June 17, 2006

Tropical Convection is Back East

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

The gist is that from taking into consideration the interactions of 4 different subseasonal time scales, a sequence depicting a coherent set of repeatable events has been derived for the Northern Hemisphere cold season from November-March. 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. Ideally it would be advantageous to post our weather-climate discussions (link at the bottom) with greater frequency to provide additional detail while having a more complete weather-climate record of attribution and prediction.

With the exception of the extreme East Pacific, SSTs are above average throughout most of the global tropics. The largest anomalies extend from the South Pacific into the Indian Ocean, with actual SSTs of at least 29-30C. The oceanic thermocline along the equatorial cold tongue remains depressed more than normal, with anomalies ~plus 1-2C at depths from 100-250m. Global SST information can be obtained from latest TAO data here, ESRL/PSD data here, and CPC data

http://www.cpc.ncep.noaa.gov/products/predictions/threats/index_gloss.html.

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

Latest satellite imagery shows an extensive area of near-equatorial tropical convection from the west central Indian Ocean to the west Pacific, with strong positive anomalies around 80E and a lesser region north of Australia. The convection across the Indian Ocean has been drifting north as well as east, which should strengthen the Indian Monsoon during the next couple of weeks. I would expect a solid consolidation of this forcing to take place north of the equator ~120E during the next couple of weeks. Afterwards, going with the obvious says to expect an eastward movement, possibility as a MJO, into the west Pacific, with a northward shift as it does (seasonal cycle). Compared to a week ago, tropical convection has become relatively suppressed over the western hemisphere ITCZs, particularly around Central America.

There is inconclusive to weak agreement among the statistical and numerical models that the current tropical convective forcing across the eastern hemisphere will behave as discussed above by the end of week 2. Please see ESRL/PSD MJO tools , BMRC MJO tools, CPC MJO tools, and http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/index.primjo.html for the details.

Zonal mean 200mb wind anomalies of ~ minus 5-15 m/s continue to propagate off the equator into the subtropics of both hemispheres, with zonal mean westerly anomalies appearing along and just north of the equator. Strong zonal mean westerly wind anomalies (~15-25 m/s; largest in the Southern Hemisphere) prevail across the northern and southern hemisphere extratropics, indicative of inter-hemispheric symmetry due to tropical forcing.

AAM anomalies have decreased to more than ~ minus 2.5 standard deviations below the 1968-1997 climatology, but with its tendency becoming positive (discussed below), based on the reanalysis data which lags 3 days from the current time. The operational data plot shows that AAM has decreased to more than 3 standard deviations below the 1979-1998 climatology (see http://www.cdc.noaa.gov/map/images/aam/glaam.gif). The largest contributions to the low global AAM continue to be from the Southern Hemisphere subtropical atmosphere, with a general zonal mean AAM distribution featuring anomalous easterlies throughout the subtropics and high latitudes, and anomalous westerly flow in the midlatitude atmospheres. The increase in the zonal mean anomalous westerly flow across ~25-40N and S may be due to eddy feedback and transport processes.

Animations of daily mean 150mb and 250mb vector wind anomalies loosely show twin subtropical anticyclones around 90-150E (one can argue others), with increasing divergence due to the tropical convection in that region. During the last week or so westerly wind anomalies have been increasing along and north of the equator from the Indian Ocean into the East Pacific. I would like to argue these westerly anomalies are appearing as the result of wave breaking of extratropical baroclinic wave trains/packets interacting with the eastern hemisphere tropical convective forcing (leading to “expected AAM fluxes”). However, that is an outstanding research issue, and needs attention for both theoretical and prediction concerns. In any case, the appearance of these upper tropospheric equatorial westerly wind anomalies is one of the components leading to the observed positive tendency in global relative AAM. I would expect the equatorial westerly wind anomalies (and AAM) to continue increasing during the next couple of weeks particularly if the Maritime Continent convection shifts toward the West Pacific.

Within the framework of the GSDM, I think we are in a summertime rendition of GSDM Stage 1, particularly since the frictional torque is positive while the global mountain torque remains (barely) negative (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, including tendency). My thoughts are to remain in Stage 1 for about another week, followed by a transition to Stage 2 during week 2 and perhaps remaining so during week 3. Forecast uncertainty remains very high, particularly given the time of year and especially with timing.

I still do think it is probable a decent area of enhanced tropical convection will come into the west Pacific during the next 1-3 weeks, along with a GSDM Stage 2. Should that be the case, this may be good news for a large part of the central USA where severe drought is being experienced. During August of 2004 and 2005 we observed this behavior, and it was a “prolific” heavy rain and severe local storms producer for the middle of the country (along with cooler than normal temperatures). Please see our past weather-climate discussions for details. Given the recent SST behaviors, perhaps the GSDM Stage 2 response may persist for more than a week or two.

Week 1 (18-24 June 2006): Tropical moisture transport from the deep tropics through the Gulf of Mexico into the eastern half of the CONUS is well established. GSDM Stage 1 is most probable, meaning a belt of strong westerlies along and south of the USA/Canada border within a Gulf of Alaska to Pacific Northwest trough-south central states ridge and trough just off the East Coast. Active and possibly severe MCSs/Derechoes (along with areas of heavy rainfall) from the Northern Rockies to the Great Lakes states with above average heat from the Plains into the parts of the East would be expected. Additionally, parts of South Texas may receive locally excessive rainfall due to nearly stationary low latitude “upper level lows” south of the ridge axis. Please see http://www.nhc.noaa.gov for the latest tropical cyclone information.

Week 2 (25-01 July 2006): A transition to GSDM 2 looks more probable to me than it did when I did my last posting. Adding to my confidence is more and more ensemble members of various numerical models are starting to capture this possible circulation change (as already dictated from weather-climate monitoring and the GSDM framework). What may be happening is that the initial conditions of the models are getting a better representation of the current weather-climate situation (consistent with both our work and experience). This suggests ridge amplification off the USA west coast into Alaska with a trough developing across the Rockies and Plains and a ridge across the Southeast. Synoptically this may appear as retrogression with amplification of the wave train discussed for week 1.

Week 3 (02-08 July 2006): GSDM Stage 2, possibly transitioning to Stage 3 (need to leave this possibility open), would be my best offering as we head into the Fourth of July weekend and after. Should we see Stage 3, it is probable the Upper Mississippi Valley and Great Lakes would have below normal temperatures with warmth across the Pacific Northwest and Inter-Mountain West. Roughly the eastern half of the country would be wet.

It appears like Southwest Kansas is going to heat up again by early next week, with maximums possibly ~100-110F around next Tuesday (with a “blow torch” strong south-southwest wind). A trend toward gradually cooler (highs still in the 90s) with increasing opportunities (best to our north) of nocturnal MCSs is probable starting roughly the middle of the week. However, I think a more decided trend toward cooler and wetter appears more likely starting next weekend into the following week. Indeed, there may be a 3-5 day period of above normal rainfall and below normal temperatures (highs only from the mid 70s-80s). Week 3 may not be excessively hot while precipitation chances decrease. Whatever the case may be for the details, I again state I do not think our weather-climate situation supports an extended period of tremendously excessive scorching apocalyptic heat with no rainfall, for at least the next month.

The time -filtered coherent modes Hovmoller plots of OLR and OLRA are at http://www.cdc.noaa.gov/map/clim/olr_modes/), velocity potential Hovmollers at http://www.cpc.ncep.noaa.gov/products/intraseasonal/vpot_tlon.html , and an animation of velocity potential overlayed on OLRAs are at http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ir_anim_monthly.shtml.

Satellite imagery and other information can be found from the following links: eastern hemisphere, full-disk west Pacific, mtsat, IO, Africa, http://www.jma.go.jp/en/gms/ ; other imagery here. Latest tropical cyclone statements can be found from http://www.nhc.noaa.gov/, while the latest 3-day averages of OLR totals and anomalies and other data can be found here

http://www.cdc.noaa.gov/map/clim/glbcir.anim.shtml (animations of various fields from the operational data)

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml (Global Tropical Hazards Assessment available from this site, along with other useful information)

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/

http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html (link to our Weather-Climate discussions)

Please see the CPC Drought Monitor for areas of dryness and the latest official outlooks and statements from the 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 on about the middle of next week.
Ed Berry

Wednesday, June 14, 2006

United Tropical Convection?

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 for the northern hemisphere cold season from November-March. 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.

Also, I am making attempts to shorten these postings for a variety of reasons. Ideally it would be advantageous to post our weather-climate discussions (link at the bottom) with greater frequency to provide additional detail while having a more complete weather-climate record of attribution and prediction.

With the exception of the East Pacific, SSTs are above average throughout most of the global tropics. The largest anomalies extend from the South Pacific into the Indian Ocean, with actual SSTs at least 29-30C. Global SST information can be obtained from latest TAO data here, ESRL/PSD data here, and CPC data

http://www.cpc.ncep.noaa.gov/products/predictions/threats/index_gloss.html.

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

Latest satellite imagery shows an intense cluster of thunderstorms along the equatorial Indian Ocean, with a much larger region extending from the Bay of Bengal east-southeast into the west central equatorial Pacific. A consolidation of eastern hemisphere tropical convection appears to be in progress (as discussed in previous postings), with the centroid at ~10N/110E. In addition, a separate region of enhancement appears to be breaking off and moving fairly rapidly into the western hemisphere, perhaps as a convectively coupled Kelvin wave (see links to coherent modes Hovmollers below). Finally, thunderstorm activity remains very intense from northern South America into western Africa, along the Atlantic ITCZ.

Since December 2005 there have 6 episodes of tropical convection evolving across the eastern hemisphere, with subsequent eastward movement. The periods have been ~30 days, including MJO components. My feeling is we are likely seeing this behavior again, understanding seasonal variations (such as northward propagation during the Boreal summer). It is probable that during the next 2-3 weeks the consolidated region of tropical convection will approach the date line, with one or more convectively Kelvin waves moving rapidly through the western hemisphere. I would also expect other basins such as the tropical Atlantic to be fairly active (due to warm SSTs), especially if there are convectively coupled Kelvin waves.

There is some agreement among the statistical and numerical models that the current tropical convective forcing across the eastern hemisphere will move east during week 2, as discussed above. Please see ESRL/PSD MJO tools , BMRC MJO tools, CPC MJO tools for the details.

A time-latitude section of 200mb zonal mean zonal wind anomalies indicates anomalies of ~ minus 5-15 m/s propagating off the equator into the subtropics of both hemispheres, with zonal mean westerly anomalies just north of the equator. Strong zonal mean westerly wind anomalies (~15-25 m/s; largest in the Southern Hemisphere) prevail across the northern and southern hemisphere extratropics, indicative of inter-hemispheric symmetry due to tropical forcing.

The trades remain relaxed with even actual surface westerly flow along the Atlantic ITCZ (with anomalous convergence); with some enhancement west of the date line (anomalies ~ minus 2-5 m/s). Interestingly, the Somalia Jet (western Arabian Sea) remains much weaker than normal, indicative of enhanced convection well to the east and a suppression of the Indian Monsoon. I would expect to see this situation change during the next couple of weeks as the current enhancement along the equatorial Indian Ocean moves north.

AAM anomalies have decreased to more than ~ minus 2 standard deviations below the 1968-1997 climatology, with its tendency still negative, based on the reanalysis data which lags 3 days from the current time. The operational data plot shows that AAM has decreased to nearly 3 standard deviations below the 1979-1998 climatology (see http://www.cdc.noaa.gov/map/images/aam/glaam.gif). The recent increase in the zonal mean anomalous westerly flow across ~25-40N and S may be due to eddy feedback and transport processes.

Animations of daily mean 150mb and 250mb vector wind anomalies loosely show twin subtropical anticyclones around 100-140E as well as across the Atlantic and Africa, linked to the tropical convection. During the last few days wave breaking from extratropical baroclinic wave packets has been fluxing AAM out of the northern subtropical atmosphere at around 15-20N, and this process has lead to the zonal mean westerly anomalies just north of the equator. Regionally these westerly anomalies have appeared across both the central Pacific and Indian Oceans. I would expect the equatorial westerly wind anomalies to increase across the central and east Pacific during the next couple of weeks particularly if the Maritime Continent convection shifts toward the West Pacific.

Within the framework of the GSDM, I think we are transitioning from Stage 4-1 (summertime rendition), particularly since the frictional torque is becoming positive while the global mountain torque remains negative (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, including tendency). My thoughts are to remain in Stage 1 for about the next 10 days followed by a transition to Stage 2 by week 3. Forecast uncertainty remains very high, particularly given the time of year and especially with timing.

I do think it is probable a decent area of enhanced tropical convection will come into the west Pacific during the next 1-3 weeks, along with a GSDM Stage 2. During August of 2004 and 2005 we observed this behavior, and it was a “prolific” heavy rain and severe local storms producer for the middle of the country (along with cooler than normal temperatures). Please see our past weather-climate discussions for details.

Week 1 (15-21 June 2006): Tropical moisture transport from the deep tropics through the Gulf of Mexico into the CONUS should be well established. GSDM Stage 1 is most probable, meaning a belt of strong westerlies along and south of the USA/Canada border within a Gulf of Alaska to Pacific Northwest trough-south central states ridge and trough just off the East Coast. Active and possibly severe MCSs/Derechoes (along with areas of heavy rainfall) from the Northern Rockies to the Great Lakes states with above average heat from the Plains into the parts of the East would be expected. Additionally, the Central/Southern Plains and especially parts of Texas may receive locally excessive rainfall due to nearly stationary low latitude “upper level lows” south of the ridge axis (residuals of wave breaking events). Please see http://www.nhc.noaa.gov/ for the latest tropical cyclone information.

Week 2 (22-28 June 2006): A transition to GSDM 2 would be probable if the tropical convective forcing moves into the west Pacific. That would suggest ridge amplification off the USA west coast into Alaska with a trough developing across the Rockies and Plains and a ridge across the Southeast. Synoptically this may appear as retrogression with amplification of the wave train discussed for week 1.

Week 3 (29 June-05 July 2006): GSDM Stage 2, perhaps 3, would be my best offering as we head into the Fourth of July weekend. Should we see Stage 3, it is probable the Upper Mississippi Valley and Great Lakes would have below normal temperatures with warmth across the Pacific Northwest and Inter-Mountain West. Roughly the eastern half of the country would be wet.

After a couple of hot days with scattered high based storms, cooler and wetter weather is likely for Southwest Kansas from ~6/16-18. In fact, locally excessive rainfall may be a concern. Next week into the weekend we should warm to above normal readings, with at least a couple of opportunities for scattered diurnal thunderstorm activity. Precipitation opportunities will increase if we evolve to GSDM Stage 2 during week 2, along with much cooler temperatures. Week 3 may not be excessively hot while precipitation chances decrease. Whatever the case may be for the details, I do not think our weather-climate situation supports an extended period of tremendously excessive scorching heat with no rainfall for at least the next month.

The time -filtered coherent modes Hovmoller plots of OLR and OLRA are at http://www.cdc.noaa.gov/map/clim/olr_modes/), velocity potential Hovmollers at http://www.cpc.ncep.noaa.gov/products/intraseasonal/vpot_tlon.html , and an animation of velocity potential overlayed on OLRAs are at http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ir_anim_monthly.shtml.

Satellite imagery and other information can be found from the following links: eastern hemisphere, full-disk west Pacific, mtsat, IO, Africa, http://www.jma.go.jp/en/gms/ ; other imagery here. Latest tropical cyclone statements can be found from http://www.nhc.noaa.gov/, while the latest 3-day averages of OLR totals and anomalies and other data can be found here

http://www.cdc.noaa.gov/map/clim/glbcir.anim.shtml (animations of various fields from the operational data)

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml (Global Tropical Hazards Assessment available from this site, along with other useful information)

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/

http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html (link to our Weather-Climate discussions)

Please see the CPC Drought Monitor for areas of dryness and the latest official outlooks and statements from the 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 this upcoming weekend.
Ed Berry

Saturday, June 10, 2006

Getting the Act Together

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 for the northern hemisphere cold season from November-March. 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.

Also, I am making attempts to shorten these postings for a variety of reasons. Ideally it would be advantageous to post our weather-climate discussions (link at the bottom) with greater frequency to provide additional detail while having a more complete weather-climate record of attribution and prediction.

SSTs have changed little since June 7th. Global SST information can be obtained from latest TAO data here, and 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 WH dynamic convectively coupled signal (initiated by a convectively coupled Kw a few weeks ago) has become less coherent during the last several days. Latest satellite imagery shows a NE-SW cloud band across the Caribbean with additional enhancement across northern South America. This cloud band, the result of interactions between the WH signal and a stalled synoptic-scale front, has significantly disrupted tropical moisture transport through the Gulf of Mexico into central Plains during the past week. A tropical depression (TD#1) has developed west of Cuba out of the enhanced frontal convection.

Tropical convection continues to expand and increase across the EH, extending from the equatorial IO into Indonesia. Convection also remains intense from the Bay of Bengal (BB) into SA, and is consolidating with the clusters farther south. The IO development is likely the result of the WH signal coming back around through central Africa, where tropical convection has also been recently enhanced. I think the consolidation process of dynamically forced and boundary forced (latter due to warm SSTs) tropical convection is in progress. The most dominate tropical forcing is already in the EH, and should remain so (with further intensification) for at least the next 1-3 weeks. A MJO may evolve from the large area of forcing.

The time -filtered coherent modes Hovmoller plots of OLR and OLRA are at http://www.cdc.noaa.gov/map/clim/olr_modes/), velocity potential Hovmollers at http://www.cpc.ncep.noaa.gov/products/intraseasonal/vpot_tlon.html , and an animation of velocity potential overlayed on OLRAs are at http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ir_anim_monthly.shtml.

Satellite imagery and other information can be found from the following links: eastern hemisphere, full-disk west Pacific, mtsat, IO, Africa, http://www.jma.go.jp/en/gms/ ; other imagery here. Latest tropical cyclone statements can be found from http://www.nhc.noaa.gov/, while the latest 3-day averages of OLR totals and anomalies and other data can be found here.

Agreement is better among the statistical and numerical models that the dominate signal of tropical convective forcing will be in the EH during week 2, as discussed above. Please see ESRL/PSD MJO tools , BMRC MJO tools, CPC MJO tools for the details.

A time-latitude section of 200mb zonal mean zonal wind anomalies indicates anomalies of ~ minus 5-15 m/s from 15S-N, with the larger anomalies south of the equator and still across the WH. Other plots show that while the trades are relaxed with even actual surface westerly flow from the East Pacific into the western Atlantic (with anomalous convergence), they are stronger than normal from the date line into the IO (anomalies ~ minus 2-5 m/s). AAM anomalies are ~ minus 1.5 standard deviations below the 1968-1997 climatology, with its tendency at about minus 2 standard deviations, 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). The recent increase in the zonal mean anomalous westerly flow across ~25-40N and S (inter-hemispheric symmetry) may be due to eddy feedback and transport processes.

With convection developing across the IO and becoming robust from the east IO into western Indonesia during week 2, the AAM tendency may become less negative (see reanalysis AAM tendency plot ) and perhaps positive as zonal mean anomalous easterlies propagate off the equator into the subtropics (with downward AAM fluxes). Within the framework of the GSDM, contributions to the tendency may include both 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).

Forecast uncertainty remains much higher than “usual”. Sources include tropical convective flare-ups from other anomalously warm tropical ocean basins such as the North Atlantic and South Pacific, and the roughly 25-day variations of the global mountain torque especially from the Andes Mountains this time of year. While I am more confident about the tropical convective forcing consolidating ~ the western MC during week 2, there is still uncertainty. For instance, should convection literally explode across the equatorial IO during weeks 1-2 and lead to suppression farther east while evolving into a MJO, I may be writing a different tune by my next update. Useful predictions at these ranges within the GSDM framework must be expressed probabilistically with years of solid verification to maximize utility.

Week 1 (11-17 June 2006): A summertime rendition (shorter wavelengths) of GSDM Stage 2-3 best describes the circulation at the start, for at least the PNA sector. A generally split flow pattern should exist along the North American west coast, with a ridge from western Canada into Alaska and a trough along the West Coast into the Rockies. This all translates to a stronger than normal jet stream across the northern and central part of the CONUS, with the possibility of active MCSs/Derechos and other severe local storm exotica (and heavy rainfall) from the central Rockies into the Plains east-southeast to around Virginia/Carolinas for a couple more days. By the end of this period, strong westerly flow is probable from the Pacific Northwest into the Northern Plains, partly the result of baroclinic wave activity currently coming off of East Asia as it interacts with the intensifying EH tropical convection. The storm track would then shift back to the north (with the “old west coast trough”) while excessive heat returns the Southwest and Southern Plains. Please see http://www.nhc.noaa.gov/ for the latest tropical cyclone information.

Week 2 (18-24 June 2006): GSDM Stage 4-1 would be probable if the tropical convective forcing plays out as discussed above. For the PNA sector, that would suggest amplification of a ridge across the central Pacific Ocean leading to a general West Coast trough with a ridge across the central into eastern part of the country. I would expect a trough to linger along the East Coast. That would continue an active MCS track across particularly from the Northern Rockies into Upper Mississippi Valley and the Ohio Valley, while excessive heat continues across the south central states. Other anomalies should be apparent.

Week 3 (25 June-01 July 2006): GSDM Stage 1 would be most probable, perhaps as a summertime rendition meaning a trough along or just off the USA northwest coast (~125-130W)-eastern Rocky Mountain/Central States ridge and East Coast trough. Above average westerly flow would continue from the northern Rockies into the Northern Plains. Depending on the amplitude of the ridge, tropical moisture transport into the southwest states may increase. This whole pattern may start shifting east late in this period.

Cooler and wetter weather is likely for Southwest Kansas for the next few days. By the end of the upcoming week, ~6/15-16 maximum temperatures ~100-110F with gusty southwest winds may occur. There may be some relief next weekend with a STJ (and the northern Plains trough) leading to clouds and at least high based storms along the lee-side trough. Afterwards, just typical summer heat for week 2 with mainly scattered diurnal storms. Precipitation opportunities may increase week 3.

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/

http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html

Please see the CPC Drought Monitor for areas of dryness and the latest official outlooks and statements from the 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 around the middle of next week.
Ed Berry

Wednesday, June 07, 2006

The Atmosphere is Confused

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.

Also, I am making attempts to shorten these postings for a variety of reasons. Ideally it would be advantageous to post our weather-climate discussions (link at the bottom) with greater frequently to provide additional detail while having a more complete weather-climate record of attribution and prediction.

With the exception of a cool region just off the coast of South America, a relaxation of trades (due to an oceanic Kw) across the central and east equatorial Pacific has resulted in an increase of cold tongue SSTs during the last couple of weeks. SSTAs vary from ~ plus .5C near 120W to even 1.5C west of the date line, with SSTs from ~22C at the South American coast (anomalies roughly minus 3C) to around 31C just south of the equator at 160E. At depth, as has been true for roughly a month, anomalies around plus 1-2C extend from 50-250m east-west along the equatorial cold tongue, meaning a slightly deeper than normal oceanic thermocline. SSTs of 29C and higher also extend from the southwest Pacific into the IO.

Latest prediction from CPC expects ENSO-neutral conditions to prevail during the next 3-6 months. Global SST information can be obtained from latest TAO data here, and 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

There are conflicting signals in regard to the tropical convective forcing. Interactions between behaviors such as the early onset of the Indian and Southeast Asian (SA) Monsoons (moist phases), other tropical convective variability, forcing from the extratropics, etc., are a few of the contributors. Per several monitoring tools such as time-filtered coherent modes and velocity potential Hovmollers, the dynamically forced convectively coupled signal is over the WH centered ~40-60W (which did contribute to the East Pacific oceanic Kw), while a boundary forced component (due to warm SSTs) remains from the Bay of Bengal east-southeast into Indonesia and the Southwest Pacific Ocean.

My feeling is the WH signal will propagate well into the EH and excite tropical convection across the equatorial IO during the next 1-2 weeks. This would be consistent with the ~30 day variability of tropical forcing that has been observed since about early December 2005. I also think the convection particularly from SA into Indonesia will persist, with an eventual consolidation of all this tropical forcing (the dynamic and boundary components) in the region of the Maritime Continent (MC) by ~ weeks 2-3. Afterwards, a MJO may evolve and propagate into the warm SSTs of the west and northwest Pacific Ocean.

The time -filtered coherent modes Hovmoller plots of OLR and OLRA are at http://www.cdc.noaa.gov/map/clim/olr_modes/), velocity potential Hovmollers at http://www.cpc.ncep.noaa.gov/products/intraseasonal/vpot_tlon.html , and an animation of velocity potential overlayed on OLRAs are at http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ir_anim_monthly.shtml.

Real-time satellite imagery presents strong tropical convection along the ITCZ from the East Pacific into western Africa. Deep moist convection also persists from the Southwest Pacific west-northwest across Indonesia into the Bay of Bengal. Suppression exists elsewhere across the tropics and subtropics. Satellite imagery and other information can be found from the following links: eastern hemisphere, full-disk west Pacific, mtsat, IO, Africa, http://www.jma.go.jp/en/gms/ ; other imagery here. Latest tropical cyclone statements can be found from http://www.nhc.noaa.gov/, while the latest 3-day averages of OLR totals and anomalies and other data can be found here.

There is some agreement among the statistical and numerical models that the WH dynamically forced tropical convective signal will emerge in the EH during week 2, as discussed above. Please see ESRL/PSD MJO tools , BMRC MJO tools, CPC MJO tools for the details.

A time-latitude section of 200mb zonal mean zonal wind anomalies indicates anomalies of ~ minus 5-15 m/s from 15S-N, with the larger anomalies south of the equator and across the WH. Other plots show that while the trades are relaxed with even actual surface westerly flow from the East Pacific into the western Atlantic, they are stronger than normal from the date line into the IO (anomalies ~ minus 2-5 m/s). Finally, animations of 150mb and 250mb daily mean vector wind anomalies loosely suggest twin subtropical anticyclones across the Pacific Ocean east of the date line. A strong baroclinic wave energy dispersion coming off of Asia interacting with these anticyclones is leading to amplification across the PNA sector as I type. This will result in the large anticyclonic circulation anomaly across western Canada by this upcoming weekend as predicted by most numerical models (models have been catching up).

AAM anomalies are still ~ minus 1 standard deviation below the 1968-1997 climatology, with its tendency at roughly 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).
With some recent increase in the zonal mean anomalous westerly flow across the extratropics, the current AAM tendency may be slightly positive. However, should convection develop across the IO during week 2 as discussed above, the AAM tendency may become negative (see reanalysis AAM tendency plot ).

Within the framework of the GSDM, contributions to that negative tendency may include both 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). Physically, we would observe the present upper tropospheric tropical and subtropical zonal mean anomalous easterlies to propagate poleward (and downward) and be replaced by westerlies.

About 10 days ago I could comfortably state that GSDM Stage 1 best described the global weather-climate situation with respect to forcing-response considerations involving SSTs, tropical convection and circulation anomalies. With the dynamical signal in the WH and the other observations discussed above, a loose GSDM Stage 2-3 situation may be more accurate. This would not be too surprising given the outlooks I made 2 weeks ago valid for this time. However, I did not expect to see the current WH signal. I was expecting a slowly evolving and coherent eastward shift of the tropical convective forcing from the Arabian Sea/North IO into the MC region. In consideration of that and the other components of the GSDM, I was predicting a “clean” GSDM Stage 1-2 transition.

Forecast uncertainty remains much higher than “usual”. 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. I am also unclear just exactly how the tropical convective forcing is going to evolve. For instance, should convection literally explode across the equatorial IO during week 2 with suppression to the east, and evolve into a MJO, I may be writing a different tune during that time. Useful predictions at these ranges within the GSDM framework must be expressed probabilistically with years of solid verification to maximize utility.

Week 1 (8-14 June 2006): A GSDM Stage 2-3 is most probable. For the PNA sector that would suggest a summer-time version (shorter wavelengths) of generally split flow along the North American west coast, with a ridge from western Canada into Alaska and a trough along the West Coast into the Rockies. The latter may project onto the positive phase of the PNA teleconnection, at times. Additionally, I would expect anomalous cyclonic flow from eastern Canada toward at least the Northern Plains/Great Lakes states. This all translates to a stronger than normal jet stream across the northern and central part of the CONUS, with the possibility of active MCSs/Derechos and other severe local storm exotica (and heavy rainfall) from the northern and central Rockies into the Plains east-southeast to around Virginia/Carolinas. Heavy rainfall may also occur across portions of the Northeast. Excessive heat may be suppressed to the Southwest and Southern Plains while fall-like temperatures may be experienced across much of the northern USA from coast-coast. Finally, there may be a tropical cyclone concern for the Bay of Campeche and portions of the Gulf of Mexico (see http://www.nhc.noaa.gov/ for latest information).

Week 2 (15-21 June 2006): GSDM Stage 4-1 would be probable if the tropical convective forcing plays out as discussed above. For the PNA sector, that would suggest amplification of a ridge across the central Pacific Ocean leading to a general West Coast trough with a ridge across the central into eastern part of the country. I would expect a trough to linger along the East Coast. That would continue an active MCS track across particularly the Northern Rockies into the Ohio Valley, with the severe local storm hazard, while heat builds across the south central states. Other temperature and precipitation anomalies should be apparent.

Week 3 (22-28 June 2006): GSDM Stage 1 may emerge, perhaps as a summertime rendition meaning a trough along/off the USA Pacific Northwest coast (~120W/130W)-eastern Rocky Mountain/central/southeast states ridge and trough along/off the East Coast. That would favor a continuation of an active storm track across much of the northern CONUS.

After a few days of maximum temperatures ~100 deg F and little rainfall, cooler and wetter weather is probable for Southwest Kansas starting ~6/11. Several nights of MCS activity (including heavy rainfall and severe local storm concerns) may be a good bet going into week 2. Maximum temperatures may drop into the mid 70s-mid 80s for a couple of days. Summer heat and dryer weather returning by next weekend would then be the scenario. Again, for at least the next 2-3 weeks, I do not think we will have a pattern of persistent excessive heat and no rainfall.

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/

http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html

Please see the CPC Drought Monitor for areas of dryness and the latest official outlooks and statements from the Storm Prediction Center not only for severe storms, but also fire weather concerns. Finally, the CPC USA Hazards Assessment 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

Saturday, June 03, 2006

Things Got Messy

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. The following text merely updates what I posted on May 31st .

With the exception of a cool region just off the coast of South America, SSTs across most of the central and east equatorial Pacific not only remain slightly above average, but have increased a bit during the past few days. As will be discussed below, complicated interactions between a Rossby wave energy dispersion (RWD)/anticyclonic wave breaking (AWB) event of an Alaskan block across the North Pacific, and a convectively coupled Kw, have produced anomalous surface westerly flow along the East Pacific cold tongue. These anomalies are ~5-10 m/s, with even some actual westerly wind flow. An oceanic Kw has resulted, and appears to be stronger than the oceanic Kw that occurred earlier during April.

SST anomalies range from ~ plus .5C to even 1.5C around the date line. SSTs vary 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 3 weeks ago, anomalies around plus 1-2C extend from 50-250m east-west along the equatorial cold tongue, meaning a slightly deeper (and deepening) 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 S. 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. However, a strong convectively coupled Kw is moving through the WH as I type (phase speed roughly 15 m/s), and appears to be centered ~40-60W. A observed from full disk satellite imagery (links below), tropical convection is quite intense from the East Pacific toward the North Atlantic ITCZs. Tropical Depression #2 is a direct result of this Kw (see http://www.nhc.noaa.gov/ for details).

Time-filtered Hovmoller plots of OLR and OLRA (see http://www.cdc.noaa.gov/map/clim/olr_modes/) objectively illustrate the above mentioned convectively coupled Kw as well as other variations of tropical forcing that have been important during the last few weeks. For instance, a convectively coupled Rossby mode lead above average rainfall across most of the Arabian Sea (weekly averaged OLRAs ~minus 70-90 W/m**2 in the latter area) during the past week. 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. Additionally, the rapid RWD event interacting with the AWB discussed above may have been initiated by the heating from the enhanced convection across the Arabian Sea.

Monitoring tools such as Hovmollers of velocity potential (CHI) and animations of CHI and OLRA now suggest the main tropical convective forcing signal to suddenly be in the WH, due to the Kw. However, I do think this is a transient situation, meaning the most robust tropical convective forcing will quickly return 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 suggests convection continuing to increase from India southeast toward much of Indonesia. I think this represents an eastward shift from the Arabian Sea. Convection remains strong across Southeast Asia and sporadic from the central Pacific Ocean to just north of the Polynesian Islands (due to warm SSTs). 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 still generally inconclusive given the weak MJO signal. However, both the Wheeler technique and 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. This, in fact, may already be starting to occur.

My feeling is that we are continuing to see 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 more robustly than currently observed. I think the convectively coupled Kw will be well into the EH in about 10 days, and the upper tropospheric divergence with that feature may lead to a rapid intensification of convection in the region of Indonesia by that time. This 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 be consistent with the eastward (and southward) shift we are starting to see. 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 both the empirical and Wheeler methods. Any west Pacific convection may combine with the Indonesian thunderstorm clusters (possibly enhanced by the Kw) 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 well off the equator (mainly into the Southern Hemisphere (SH) due to the seasonal cycle) and has been replaced by easterlies. 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 ~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 (see http://www.cdc.noaa.gov/map/clim/glbcir.anim.shtml ) present a signal of twin subtropical anticyclones centered ~ 60 deg. east longitude, as well as ~160W thanks to the Kw. Also, weak upper equatorial tropospheric westerly wind anomalies have started to appear across portions of Indonesia, which may signal the development of a MJO.

Rapid wave energy dispersions affecting the PNA sector continue from the EH subtropics. For instance, during the last couple of days yet another blocking structure has appeared around Kamchatka tied with the North IO convection moving east. I believe this may be a “carry over nonlinear eddy feedback process” from the 2005-06 cold season. As shown by plots of zonal mean AAM flux divergence, there is now convergence of AAM around 30-40N (where there was divergence a few days ago), leading to a strengthening of westerly flow across the North Pacific. So, instead of fluxing zonal mean AAM from 30-40N which was due to the AWB of the Alaska block, zonal mean AAM is now being converged in that latitude band. I attribute all that to the eastward shifting of the North IO convection interacting with a high latitude retrogressive transient that started in Europe during late April (latter discussed in past Blogs and ESRL/PSD weather-climate discussions).

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.

I maintain that GSDM Stage 1 still best describes the global weather-climate situation. However, things are messy, and once can easily argue we have a Stage 3 global circulation with generally GSDM Stage 1 tropical convective forcing. Understanding the seasonal cycle, we saw a situation similar to our current one back in December 2005 (see past weather-climate discussions on the ESRL/PSD web site).

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, after some messy rearrangements which were discussed above, I think the circulation working with the warm SSTs is going to re-establish more robust EH tropical convective forcing in the region of Indonesia during week 2. 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 east toward the western Pacific during late 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 3 Blogs, and I am going to stay with it. Most ensemble prediction systems (EPS) do not show this since models do not predict tropical convection very well after about 4-5 days. However, there are hints of this possibility starting to emerge not only from the Wheeler and coherent modes techniques, but also from the GFS and CDC EPSs.

I continue to state 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. The sudden and not predicted (by me) emergence of a strong WH convective signal thanks to the Kw did not help matters any. I have also got to start wondering what the ramifications from the warming of the East Pacific cold tongue due to the oceanic Kw will have on the future of the weather-climate situation.

In the outlooks that follow, I am still going to key on a possible intensification of the tropical convection ~ MC during week 2, possibly shifting toward the west Pacific warm SSTs as a MJO during week 3. Current satellite trends and monitoring tools maintain my confidence for that notion. 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 (4-10 June 2006): GSDM Stage 1 is most probable, but with complications such as a summertime rendition of an extended East Asian/North Pacific jet. The models and I have struggled with this during the past week. All models generally show, with low ensemble spreads, the pattern of an east Pacific trough, Rockies to Great Plains ridge and East Coast trough through much of next week. 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.

As I discussed in my last Blog, this “ridge pattern” for the lower 48-states would likely not persist, in opposition to the predictions of most numerical models. Models such as the ECMWF, GFS and Canadian indeed now do predict this ridge to move east while a trough develops across the western USA, all starting by roughly next weekend.

Week 2 (11-17 June 2006): GSDM Stage 1 would be most probable, possibly transitioning to Stage 2 late. I am slowing down my evolution from the May 31st Blog thanks to the nonlinear feedbacks (discussed above) that I did not expect. Also, understanding there will be a northwestward shift, the general pattern of a western states trough and south central to southeast USA ridge similar to last spring would be probable (including the well known temperature and precipitation anomalies). The added westerly flow across the North Pacific looks to delay a true summertime rendition (with the shorter wavelengths) of GSDM Stage 1 for the USA.

If we 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).

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 (18-24 June 2006): GSDM Stage 2 continuing and/or emerging would be most probable.

Specifically for southwest Kansas, I think we can say there is some truth to my outlooks for weeks 2-3 since most models and their ensemble are now lending support (all part of a complete forecast process) . Well above average temperatures and below normal precipitation is a good bet through most of next week. However, 1 or 2 surprises may occur, and will have to be monitored. By next weekend, even with the storm track to our north, jet streaks rotating northeast along the STJ may produce some decent storms along a dryline/lee side trough. Also, a front could easily stall across this part of the world even with southwest flow. If we transition to GSDM Stage 2, our rain chances will increase and temperatures will cool down. That transition may start during week 2. Whatever the case may be, at least for the next few weeks, the notion of a “sufficating hot/dry anticyclone” building across this region appears less probable.

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.

All weather-climate discussions can be obtained from the following link:

http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html

These weather-climate discussions are done as time permits.

I will attempt another Blog posting during the middle of next week.
Ed Berry