Atmospheric Insights

http://www.cdc.noaa.gov/map/images/sst/sst.long.time.gif

http://www.cdc.noaa.gov/forecast1/IndoPacific.frcst.html (note the initial projection)

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/index.primjo.html (link 18)

As was offered on my 23 July posting, Eastern Hemisphere tropical convective forcing has been slowly propagating east-northeast toward the northwest Pacific Ocean (~5-6m/s phase speed). Full disk satellite imagery shows this enhanced rainfall extending from India east-southeast to north of New Guinea, centered on approximately the Philippines. Forced by the Southern Hemisphere extratropics, separate flare-ups continue over the western equatorial Indian Ocean. The latter has been a recurring feature since at least early June. WH (2004) MJO plots through 31 July indicate a slightly less than 1 sigma projection in octant 4 of phase space (w/wo interannual component), having little eastward movement during the last few days (more said below).

During the last half of July dynamical processes tied to the tropical convection and the extratropics worked to add global westerly wind flow. In fact, relative AAM peaked just above the R1 data climatology ~30 July. Anomalous zonal mean westerly wind flow was generated in the northern equatorial atmosphere around mid-July, only to propagate poleward and downward since. The latter has been in the presence of other midlatitude zonal bands of anomalous westerly wind flow. Particularly in the austral winter Southern Hemisphere storm track regions, frictional dissipation of this westerly wind flow has been occurring over the last couple of weeks. In fact, the zonal mean frictional torque anomaly around 25S has been minus 2 Hadleys and lower.

Continuing, my point is that I think once again westerly wind flow is decreasing globally. For example, Rossby wave energy dispersions (RWDs) tied to the Eastern Hemisphere tropical convective forcing arcing across the South Pacific Ocean is contributing to a strong negative Andes mountain torque. That along with other complicated dynamical processes (to save space!) has forced the global relative AAM tendency to roughly minus 20 Hadleys allowing the WB (2008) GWO to orbit solidly into octant 8-1 of phase space (averaging period issues understood).

One bottom line for predictive purposes is that I do expect a signal having a MJO component to propagate through the Western Hemisphere during the next few weeks. Most statistical and dynamical MJO forecasts utilizing the WH (2004) methodology do not support this notion very well.

However, I think it is less likely there will be the strong enhancement around the Americas as observed ~mid June-mid July. In addition to dynamical forcing from extratropical RWDs, I think the latter may have involved some constructive interference between an equatorial Atlantic convectively coupled Rossby mode and the previous MJO. The Rossby mode may have been a response to what was persistent tropical convective forcing across the eastern equatorial Atlantic Ocean during boreal late winter-spring. Above average SSTs, perhaps due to an "Atlantic El-Nino", contributed to that enhanced convection.

Another bottom line is that the quasi-stationary component to our global circulation base state favoring a low AAM regime has not completely gone away. The recurring convective flare-ups over the western equatorial Indian Ocean per above is a manifestation of this. Hence I do think the WB (2008) GWO is probable to loosely orbit tilted toward phase 3 (La-Nina base state) “until further notice”. In fact, I remain concerned some reprisal of the “2007-08 season of the witch” may occur this upcoming boreal cold season.

On my 23 July discussion I suggested with low confidence a “pattern shift of sorts” across the USA may occur favoring a ridge around the west coast and a trough in the middle of the country going into this month. None of the numerical models or official predictions suggested this. Latest model runs now favor a situation similar to this regional scale response for next week. Hence the intense heat that is about to expand eastward across the central and eastern states is probable to last only a few days.

However, my feelings for success of this subseasonal prediction are limited and mixed. I was favoring a stationary pattern given by phases 3-4 of the GWO 250mb psi and temperature anomaly composites. Instead, a relatively large orbit in GWO phase space occurred.

For weeks 1-3, interestingly enough, with variations understood, phases 3-4 and 4-5 of the GWO anomaly composites (250mb psi and temperature) along with MJO temperature anomaly phases 4 and 5 appear to be the most probable outcome for the country. Again, these are composite signals and need to be updated. Also, given recent relatively weak weather-climate signals and a tendency for “fading in and out (not discussed)”, my confidence remains low.

As the Plains cool down next week, intense MCS activity may shift southward impacting locations from eastern Colorado-Wyoming into at least Iowa and Missouri. The MCS storm track is probable to shift back to the northeast as intense heat may return to the Central and Southern Plains weeks 2-3. Other locations possibly impacted by periods of heavy rainfall and severe local storms are portions of the eastern states weeks 1-3.

Intense to severe tropical thunderstorm activity should shift east and north through portions of India, Southeast Asia and the northwest Pacific Ocean during the next 1-2 weeks. Locations that may be hardest hit include the South China Sea and the Philippines into the west central Pacific Ocean. Going along will be the risk of tropical cyclone development. Persistent tropical forcing is also likely across the western equatorial Indian Ocean. During weeks 2-3, while tropical thunderstorm activity may weaken slightly across the Eastern Hemisphere, some enhancement is likely over the Americas. The risk of tropical cyclones may increase across the East Pacific Ocean week-2 and Atlantic by week-3 (above climatology).

Please see the latest official tropical cyclone forecasts for all basins. I trust the expertise of the appropriate meteorological centers to alert the public of additional weather hazards worldwide.

Appendix

Links to CPC and PSD ENSO discussions:

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml

http://ds.data.jma.go.jp/tcc/tcc/products/clisys/index.html

The following is a link to information about the stratosphere and other nice monitoring tools:

The following is a link to NCEP model verifications (surf around for lots more).

http://www.cpc.ncep.noaa.gov/schemm/z500ac_wk2_na.html

The following is a link discussing recent global weather and related events.

http://www.wmo.ch/pages/mediacentre/news/index_en.html

These are probabilistic statements. We hope that an opportunity will arise for us (soon) to allow our dedicated web page effort to mature, expediting objectively and accountability. This web page effort will hopefully include an objective predictive scheme for the GWO with hindcasts.

The WB (2007) paper on the GSDM has been published in the February issue of MWR. In addition, the first of a two-part paper has been submitted to MWR where WB formally introduce the GWO. A pdf version can be downloaded from the following link

http://www.cdc.noaa.gov/map/clim/gsdm.composites.shtml

Overlapping seasonally varying subseasonal composites for variables such as surface temperature, precipitation, geopotential height and streamfunction anomalies are planned on being posted on the web site mentioned above and presented in part-2 of our paper. We want to emphasize notions such as global-zonal mean-regional scale linkages as well as forcing-response-feedback (with subsequent interactions) relationships. An important purpose is to provide a dynamical weather-climate linkage framework to evaluate the numerical models in a sophisticated manner as part of a subseasonal (and any time scale) forecast process, in addition to a climate service for all users. Relying on the numerical models alone is a cookbook!

Given shift work and travel, updates are extremely difficult. I hope to do another discussion late next week.

Ed Berry

Wednesday, July 23, 2008

Burn the Cookbooks!!!

“The views expressed are those of the author and do not necessarily represent those of the National Weather Service.”

Please keep in mind the ESRL/PSD GSDM web link, below, while reading this discussion.

The general thought is “ENSO neutral conditions with some lingering effects of La-Nina circulation” for at least the next few months. While in the views of many there is some truth to a statement such as the latter, care must be taken not to overlook the always important details of the subseasonal dynamics (which do impact seasonal outcomes). For instance, one response has been the warming of the equatorial east Pacific Ocean during the last several months, perhaps reflective of a “~year (-1) of a Rasmussen and Carpenter (1982) warm event scenario”. Please see links below, and stay tuned.

http://www.wmo.int/pages/prog/wcp/wcasp/enso_update_latest.html

http://iri.columbia.edu/climate/ENSO/currentinfo/technical.html

http://www.cdc.noaa.gov/map/images/sst/sst.long.time.gif

http://www.cdc.noaa.gov/forecast1/IndoPacific.frcst.html (note the initial projection)

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/index.primjo.html (link 18)

As expected, Eastern Hemisphere tropical convective forcing has become quite intense, currently centered ~5N/100E. Most numerical and statistical MJO prediction schemes did a poor job with this evolution. Reasons include a failure to capture the role of extratropical dynamical processes explained by the WB (2008) GWO. Continuing, there was also difficulty for many week-2 numerical ensembles to predict the extratropics, with the ACC of the NCEP GFS dipping well below zero for the North American sector. The latter are well known issues by WB, and hopefully an opportunity will arise to quantify it statistically.

Three-day averaged OLRA have exceeded minus 90 W/m**2 with the Indian Ocean severe thunderstorm clusters. The area of enhanced tropical rainfall is oriented northeast-southwest, not only enhancing the monsoon systems, but also frontal bands even across southeast China. Per WH (2004) phase space diagrams, there is a less than 1 sigma MJO projection in octant 3. Leaving the interannual component in, the projection is greater than 1 standard deviation, which is more realistic. I do expect this tropical forcing to continue propagating east and north during the next 1-3 weeks.

During the last couple of weeks there has been some attempt to rejuvenate our low AAM base state. Leaving the westerly QBO phase in, global relative AAM dipped to roughly 1 AMU below the R1 data climatology earlier this month. With the classic transition of Eastern Hemisphere tropical upper tropospheric circulation anomalies to Indian Ocean (west Pacific Ocean) anticyclones (cyclones), equatorial Pacific westerly wind flow anomalies have appeared (roughly 20-25m/s around the date line). Particularly for the Southern Hemisphere, there has been poleward propagation of zonal mean zonal wind flow anomalies including easterlies shifting into the subtropical atmospheres.

These are only a handful of many reasons why global relative AAM tendency spiked to ~plus 20 Hadleys forcing the WB (2008) GWO into approximately octant 4 of phase space on 20 July. Both AAM tendency and the GWO are headed back down (through 21 July), and whether the rejuvenation discussed above is a longer term signal remains unclear (not to contradict other weather-climate signals).

Broadly, there continues to be good tropical-extratropical coupling, including interhemispheric meridional symmetry of zonal mean zonal wind anomalies favoring anomalous midlatitude ridges. Comparing recent daily mean 150mb vector wind anomalies to the MJO composites, phase 3 of 250mb psi is loosely representative (“apples and oranges” issues understood). For instance, there is a well defined Rossby wave energy dispersion (RWD) signal from the west Pacific Ocean cyclones that links up the trough-ridge-trough pattern across North America.

The careful reader will also see these signals in the GWO composites. Avoiding more length and confusion, there is ~50 day period between the recent minima in the time series of the global frictional torque. This leads to the point that decay time scale processes explained by the WB (2008) GWO are currently at least as equally important as any MJO contribution. Hence my feeling (one reason) why the notions suggested by the phase 3-4 composites of the GWO may be representative for roughly weeks 2-3. We need to remember these composites are still centered on 1 July (should be updated soon), and that using these must be defended on sound scientific reasoning, not “shoe horned”. In any case, this thought is consistent with my discussion posted on 12 July.

For the North American sector, perhaps ~days 10-20 (roughly 2-13 August) ridge amplification off the west coast into Alaska leading to an approximate reversal of circulation anomalies across the USA is a possibility. My confidence in this scenario is not high; however, I feel it should be “put on the table”. There is little suggestion of this scenario from the models and certainly the official USA week-2 forecast. In fact, the suggestion of warmth officially across the northern states is also inconsistent with the MJO signal. The "meteorological reasoning" for the official week-2 forecast is based on seemingly subjectively blending various models, including deterministic runs (my dog (angry Rottweiler) does not like this!).

The probable USA temperature patterns can be seen from the 2m air composite signals. However things pan out, a shift toward below normal air temperatures from the Great Lakes extending southward toward the Central Plains should be considered. Once again, locations periodically focusing on the Northern and Central Plains into the Ohio Valley are the most probable storm track for MCS activity. Other locations possibly impacted by periods of heavy rainfall and severe local storms are portions of the eastern states.

Intense to severe tropical thunderstorm activity should shift east and north through portions of India and Southeast Asia during the next 1-2 weeks. Included are frontal bands across southeast China. By week-3 the most intense tropical convection may focus on the northwest Pacific Ocean including the South China Sea and the Philippines. The tropical cyclone hazard may also increase for these areas. Whether or not convection also propagates eastward along the equator to near the date line is unclear (may cause an equatorial westerly wind burst). The tropical cyclone hazard for the Western Hemisphere should be diminished weeks 1-2 (hybrids always understood, including the one currently northeast of the Philippines).

Please see the latest official tropical cyclone forecasts for all basins. I trust the expertise of the appropriate meteorological centers to alert the public of additional weather hazards worldwide.

Appendix

Links to CPC and PSD ENSO discussions:

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml

http://ds.data.jma.go.jp/tcc/tcc/products/clisys/index.html

The following is a link to information about the stratosphere and other nice monitoring tools:

The following is a link to NCEP model verifications (surf around for lots more)

http://www.cpc.ncep.noaa.gov/schemm/z500ac_wk2_na.html

The following is a link discussing recent global weather and related events

http://www.wmo.ch/pages/mediacentre/news/index_en.html

The WB (2007) paper on the GSDM has been published in the February issue of MWR. In addition, the first of a two-part paper has been submitted to MWR where WB formally introduces the GWO. A pdf version can be downloaded from the following link

http://www.cdc.noaa.gov/map/clim/gsdm.composites.shtml

Given shift work and travel, updates are extremely difficult. I hope to do another discussion around the weekend of 2-3 August.

Ed Berry

Saturday, July 12, 2008

Another Weather-Climate Crossroad

“The views expressed are those of the author and do not necessarily represent those of the National Weather Service.”

Following the lead started last week, please keep in mind the ESRL/PSD GSDM web link, below, while reading this discussion.

Below are the links to various sources of global SST information. Overall, any interannual component of variability involving the SSTs is still unclear. There are some aspects similar to a year ago appearing such as the loose spatial pattern of anomalous warm-cool-warm of equatorial/tropical SSTs from the Indian Ocean into the west central Pacific Ocean. There has been little change since at least a week ago.

http://www.wmo.int/pages/prog/wcp/wcasp/enso_update_latest.html

http://iri.columbia.edu/climate/ENSO/currentinfo/technical.html

http://www.cdc.noaa.gov/map/images/sst/sst.long.time.gif

http://www.cdc.noaa.gov/forecast1/IndoPacific.frcst.html (note the initial projection)

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/index.primjo.html (link 18)

Full disk satellite imagery and other tools used to help understand evolutionary processes still indicate multiple regions of enhanced tropical convective forcing. Similar to a week ago, they include the equatorial Indian Ocean into the Eastern Hemisphere monsoon systems and the eastern Pacific Ocean ITCZ into the Americas. Some important differences, however, are increased suppression over the west central Pacific Ocean and a significant increase in coverage and intensity along the equator over the Indian Ocean. In fact, latest 3-day averaged OLRA for the latter are ~minus 70-90 W/m**2. This increase of Indian Ocean forcing was expected a week ago, linked to the dynamics of complicated Rossby wave energy dispersions (RWDs) arcing through the extratropics, particularly the Southern Hemisphere (more said below).

As I have been also expecting to happen for at least the past 2 weeks, global relative AAM is decreasing. In fact, ~7 July the calculated relative AAM tendency was ~minus 30 Hadleys. This was one of the largest negative magnitudes since December 2007. In contrast to the computed tendency (GWO2), the latter takes into consideration the zonal mean AAM transport signal. Updated through 10 July relative AAM was roughly 1 AMU below the R1 data climatology with the calculated tendency of ~minus 10 Hadleys.

While not feasible to discuss the details here, from daily monitoring and working to have a better understanding of the dynamics involved, I feel fairly comfortable offering attribution to this recent AAM behavior. Much of this removal of global westerly wind flow has been through frictional dissipation of poleward and downward propagation of zonal mean westerly wind flow anomalies into the midlatitude storm track regions for at least the past several weeks. That has been especially true of the Southern Hemisphere, given austral winter, having zonal mean negative frictional torque anomalies of more than 2 Hadleys ~50-60S contributing to a global frictional torque of ~minus 20 Hadleys around 1 July. Interesting question to ask is if this behavior is a loose mirror image to what occurred last February for boreal winter? The point is this type of understanding helps to anticipate subseasonal behaviors including the MJO, as part of the GWO. All numerical models will do generally poorly with these types of processes even after a few days into their prediction cycles.

Updated through 10 July, both the WH (2004) and WB (2008) measures of the MJO and GWO respectively had similar locations in phase space. Both were in approximately octant 1 having projections greater than 1 sigma. I think there is good coupling between the tropics and extratropics, including (again) arguably meridional symmetry of zonal mean zonal wind anomalies. As bands of zonal mean westerly wind flow anomalies shift poleward through the extratropical atmospheres, easterly wind anomalies are increasing in the tropical and subtropical atmospheres. This all goes “hand in hand” with the MJO dynamical signal of tropical convective forcing starting to return to the Eastern Hemisphere, particularly the Indian Ocean.

Referring to the GWO and MJO composites for ~250mb streamfunction (psi) and 2m air temperature, the ongoing progressive synoptic trough currently in the central USA and the model predictions of another for the USA Pacific Northwest are consistent with roughly phases 1-2. Most week-2 ensembles were predicting the current trough to dig into the western USA, which did not occur (another issue).

While unclear about the time scale, I do think the spatial patterns depicted by especially GWO phases 3-4 is where the global circulation is going. My suspicion for the latter is ~weeks 3-4 (by early August). Until then, the patterns illustrated by MJO phases 2-3 may be the best offering of a prediction roughly weeks 1-2. The bottom line is I still have my concerns for some rejuvenation of the low AAM base state going into the upcoming boreal cold season. Obviously exact weather ramifications are unclear. Statements like, “ENSO neutral with lingering La-Nina circulation”, while perhaps currently true, tell you nothing about the critically important global subseasonal dynamics (as measured by the GWO).

The probable USA temperature patterns per above can be seen from the 2m air temperature composite signals. Again, remember these are composites and individual cases can be much stronger. Locations periodically focusing on the Northern Plains into the Ohio Valley are the most probable storm track for MCS activity. That includes more heavy rainfall for locations such as Iowa and the Upper Mississippi Valley.

Intense to severe tropical thunderstorm activity is probable to increase from the equatorial Indian Ocean into the monsoon systems and frontal bands of India and Asia during the next few weeks. The west and northwest Pacific Ocean will remain a “wild card”, including the possibility of tropical cyclone spin-ups threatening the Philippines and Southeast Asia. The East Pacific Ocean tropical cyclone hazard should wane by week-2.

Anomalous upper tropospheric twin tropical anticyclones are well defined across the Western Hemisphere, while they slowly propagate through Africa into the Indian Ocean. This situation is favorable for additional strong African easterly waves. Please see the latest official tropical cyclone forecasts for all basins. I trust the expertise of the appropriate meteorological centers to alert the public of additional weather hazards worldwide.

Appendix

Links to CPC and PSD ENSO discussions:

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml

http://ds.data.jma.go.jp/tcc/tcc/products/clisys/index.html

The following is a link to information about the stratosphere and other nice monitoring tools:

The following is a link to NCEP model verifications (surf around for lots more).

http://www.cpc.ncep.noaa.gov/schemm/z500ac_wk2_na.html .

The following is a link discussing recent global weather and related events.

http://www.wmo.ch/pages/mediacentre/news/index_en.html

http://www.cdc.noaa.gov/map/clim/gsdm.composites.shtml

Overlapping seasonally varying subseasonal composites for numerous variables including surface temperature, precipitation, geopotential height and streamfunction anomalies are planned on being posted on the web site mentioned above and presented in part-2 of our paper. We want to emphasize notions such as global-zonal mean-regional scale linkages as well as forcing-response-feedback (with subsequent interactions) relationships. An important purpose is to provide a dynamical weather-climate linkage framework to evaluate the numerical models in a sophisticated manner as part of a subseasonal (and any time scale) forecast process, in addition to a climate service for all users. Relying on the numerical models alone is a cookbook!

Given shift work and travel, updates are extremely difficult. An update is unlikely next weekend, 19-20 July. I hope to do another discussion ~23 July.

Ed Berry

Friday, July 04, 2008

Reprisal -- Is the Witch Dead???

“The views expressed are those of the author and do not necessarily represent those of the National Weather Service.”

I am going to work to make these postings shorter and focus more on the products contained in the experimental dedicated web page that is only in the infancy of development, per Appendix in previous discussions. One important purpose of these discussions is to provide a much needed climate service for all users. The web link is

To keep us “vigilant” about the interannual variability component, I will leave the following links in. While there has been a bit more respectable warming of equatorial eastern Pacific Ocean SSTs (~ plus 3-4C anomalies at 50m depth) along with other measures suggestive of a possible eventual evolution toward an El-Nino, I think the interannual signal remains unclear. I will give attention in these postings should that change. Please remember that “ENSO neutral” does not at all imply there will be a lack of robust subseasonal events leading to global high impact weather situations.

http://www.wmo.int/pages/prog/wcp/wcasp/enso_update_latest.html

http://iri.columbia.edu/climate/ENSO/currentinfo/technical.html

http://www.cdc.noaa.gov/map/images/sst/sst.long.time.gif

http://www.cdc.noaa.gov/forecast1/IndoPacific.frcst.html (note the initial projection)

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/index.primjo.html (link 18)

Full disk satellite imagery etc. indicates multiple regions of enhanced tropical convective forcing. These include the Eastern Hemisphere monsoon systems into the northwest Pacific Ocean, the Eastern Pacific Ocean ITCZ through the Americas and the western Indian Ocean. Complicated interactions with the extratropics have resulted in this pattern, and can only be understood with rigorous daily monitoring utilizing the WB (2007) GSDM. In any case, a strong MJO projection in octant 1 of ~2 standard deviations in WH (2004) phase space, with the very important interannual base state left in, has resulted. To me, this is still MJO #6 since boreal fall 2007.

Updated through 2 July, there is little circulation projection in the WB (2008) GWO phase space. However, this phase space depicts a dynamical evolution of the global atmosphere (not static!!! --- insert angry Rottweiler). For instance, as part of several attempts to increase westerly wind flow globally since late 2007, such has been the case since roughly mid May. Bands of zonal mean westerly wind flow anomalies have been propagating poleward off the equator with downward transport (by the baroclinic eddies), only to undergo frictional dissipation in the midlatitude storm tracks. Even though the latter has recently been most robust in the Southern Hemisphere given austral winter, for the Northern Hemisphere there has been zonal mean dissipation ~20 and 50N. Hence the global friction torque is ~minus 20 Hadleys, one of the lowest values since late 2007.

The point is that I expect to see global relative AAM decrease very soon (restatement from my last posting). Relative AAM tendency is probable to become strongly negative as the global mountain torque becomes negative and a poleward transport signal develops in both hemispheres (please see description and schematic on the web page). Hence the WB (2008) GWO is likely to orbit into octants 2-3 during the next 1-3 weeks. This will again be a situation where both the WH (2004) and WB (2008) phase spaces are similar, ~2-3. Evolutions such as this may rejuvenate our low AAM base state.

Referring to the MJO composites for ~250mb streamfunction (psi) and 2m air temperature, octants 2-3 suggest an increased probability of a northwestern USA trough with a ridge across the eastern states. The 2m air temperature patterns are the expected “cool west-warm east”. Keep in mind these are composite signals, hence relatively weak. The GWO composites are similar, but show a nice progression of coolness shifting into the central part of the country and heat returning to portions of the west (still warm for much of the east). I prefer the latter and suspect phases 3-4 of the GWO will be most probable by ~week 3 based on results discussed in our submitted paper to MWR. Most models are catching on to this notion for weeks 1-2.

The precipitation patterns should be well understood. After a fairly quiet few weeks (relatively speaking), intense to severe MCS activity for much of the Northern Plains into the Ohio Valley is a concern starting next week. This activity may become particularly intense in terms of flooding rainfall weeks 2-3 while drifting slowly southward (focus on Iowa and Missouri?).

Intense to severe tropical thunderstorm activity is probable to increase from the Indian Ocean into the monsoon systems and frontal bands of India and Asia during the next couple weeks while the west and northwest Pacific Ocean stays sporadic. In fact, tropical cyclone spin-ups for the latter threatening the Philippines and Southeast Asia cannot be ruled out. The East Pacific Ocean tropical cyclone hazard should wane during week-2.

The warm north tropical Atlantic Ocean basin defied my concerns related to tropical cyclone climatology expressed a week ago with the development of Tropical Storm Bertha (was not surprised). With upper tropospheric anomalous twin tropical anticyclones returning to Africa and the Indian Ocean from the Western Hemisphere during the next 1-2 weeks, additional strong African easterly waves are probable. Please see the latest official tropical cyclone forecasts for all basins.

Other severe/high impact weather continues internationally. I trust the expertise of the appropriate weather centers to alert the public of additional weather hazards worldwide.

Appendix

Links to CPC and PSD ENSO discussions:

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml

http://ds.data.jma.go.jp/tcc/tcc/products/clisys/index.html

The following is a link to information about the stratosphere and other nice monitoring tools:

The following is a link to NCEP model verifications (surf around for lots more).

http://www.cpc.ncep.noaa.gov/schemm/z500ac_wk2_na.html .

The following is a link discussing recent global weather and related events.

http://www.wmo.ch/pages/mediacentre/news/index_en.html

http://www.wmo.int/pages/prog/wcp/wcasp/enso_update_latest.html

Overlapping seasonally varying subseasonal composites for variables such as surface temperatures, precipitation and streamfunction anomalies are planned on being posted on the web site mentioned above and presented in part-2 of our paper. We want to emphasize notions such as global-zonal mean-regional scale linkages as well as forcing-response-feedback (with subsequent interactions) relationships. An important purpose is to provide a dynamical weather-climate linkage framework to evaluate the numerical models in a sophisticated manner as part of a subseasonal (and any time scale) forecast process. Relying on the numerical models alone is a cookbook!

Given shift work and travel, updates are extremely difficult. I hope to post another discussion the weekend of 12-13 July.

Ed Berry

Saturday, June 28, 2008

Return of the (USA) Wicked Ridge from Hell

“The views expressed are those of the author and do not necessarily represent those of the National Weather Service.”

I want to shorten these discussions (and still failed). There has not been any change in the overall spatial patterns of tropical and extratropical SSTs. The following are links to SST information, including an ENSO posting by the WMO. As stated by the latter, careful monitoring (including subseasonal atmospheric variability – my part) is critical during the next several months for the future of ENSO. Again, I emphasize that I am discussing the interannual aspect of coupled ocean-land-atmosphere variability where ENSO is a component.

http://iri.columbia.edu/climate/ENSO/currentinfo/technical.html

http://www.cdc.noaa.gov/map/images/sst/sst.long.time.gif

http://www.cdc.noaa.gov/forecast1/IndoPacific.frcst.html (note the initial projection)

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/index.primjo.html (link 18)

Full disk satellite imagery shows multiple regions of enhanced tropical convection. Loosely, these are centered from the equatorial western Indian Ocean into the Eastern Hemisphere monsoon systems, the west central Pacific and in the region of the Americas. Hovmoller plots and other diagnostic tools show there has been a slow eastward shift of tropical convective forcing since early May. Per WH (2004) phase space plots, a MJO component of this forcing is present, currently in octant 8 ("Western Hemisphere and Africa").

The extratropics have contributed to the eastward shift of tropical convective forcing. Included are north-south mountain massifs, having broadly positive global mountain torque events of ~20 Hadleys late May, mid-June and most recently. The latter involved the Southern Hemisphere mountain ranges such as the Andes and those over Antarctica. The tropical forcing and stochastic mountain torque events are some of the subseasonal dynamics captured by the WB (2007, 08) GWO.

Complicated interactions of processes briefly mentioned above have worked to add westerly wind flow to the global atmosphere. For example, zonal mean westerly wind flow anomalies of ~5m/s have shifted off the equator into the Northern Hemisphere subtropical atmosphere. There was also a (very) slight transient reversal of upper tropospheric tropical circulation anomalies across the Eastern Hemisphere a few days ago (~24 June), with twin cyclones trying to evolve in the region of the Indian Ocean along with downstream anticyclones. Hence the WB (2007, 08) GWO orbited in phase space to octant 5 on 22 June, before collapsing. Including the westerly QBO phase of the stratosphere, global relative AAM through 26 June was near the R1 data climatology. However, I do expect to see relative AAM decrease (abruptly like the USA stock market???) during the next few weeks.

There is evidence of some tropical-extratropical coupling returning. The WH (2004) MJO and WB (2007, 08) GWO plots are starting to line up in phase space; ~ octants 8-1-2-3 are probable during the next few weeks. Support for this notion includes a negative global frictional torque (~10 Hadleys – GWO component) and a few predictions (ex., POAMA and ECMWF) of the WH (2004) RMM index to orbit to phase 3 by week-3. Physically this means a return to a La-Nina base state and/or a re-enforcement of a stationary low AAM regime that has been present for at least the past year. Seasonal implications are still unclear. The point is that the atmosphere is orbiting in phase space around what may still be the “La-Nina attractor”. This evolution is the foundation for subseasonal predictive information offered below.

In my last posting I suggested a western/northwestern USA trough for the upcoming week. Instead, the wicked ridge (from Hell) of the western USA is returning. Based on subseasonal composites currently being developed, similar to July 2007, anomalous summertime ridge conditions for the western states are probable during phases 3-4 of the GWO. Like that observed during boreal winter 2007-08, these same phases of the GWO favor a western USA trough during the cold season given wavelength considerations (still the season of the witch leading to the wicked ridge of the west?). Based on these composites and rigorous daily monitoring, I had indications of my poor assessment 2 days later. A dedicated web page effort where these subseasonal composites and other tools are available would have greatly facilitated an update.

As all models now show (the GFS has been playing catch-up), an amplified western USA ridge and eastern states trough is likely week-1. I do think this ridge will expand into the central states and Deep South ~week 2, before possibly re-amplifying west of Continental Divide weeks 3-4 allowing a trough in the region of the Mississippi Valley. Thus intense western heat may briefly expand into portions of the eastern USA week-2 after a cool week-1. There will be an active MCS storm track along the “southern edge of the westerlies” focused at times on the mid and upper Mississippi Valley states ~weeks 2-3. The "Desert Southwest monsoon" may get off to a robust start during the next couple of weeks, much like climatology suggests. Other ramifications should be understood.

Intense to severe tropical thunderstorm activity is probable to increase from the Indian Ocean into the monsoon and frontal rain band systems of India and Asia weeks 2-3 while the west and northwest Pacific Ocean is sporadic. The East Pacific Ocean tropical cyclone hazard should wane during week-2. I would have a greater concern for cyclones across the tropical Atlantic Ocean basin weeks 1-2 if it were August-September. Please see the latest official tropical cyclone forecasts for all basins.

Other severe/high impact weather continues internationally. I trust the expertise of the appropriate weather centers to alert the public of additional weather hazards worldwide.

Appendix

An experimental quasi-phase space plot of the GSDM utilizing time series of normalized global relative AAM time tendency (Y-axis) and normalized global relative AAM anomaly (X-axis) can be found at

http://www.cdc.noaa.gov/map/clim/gsdm.shtml

This phase plot is being re-done, as is the web site. Stay tuned. We call the behavior of this plot the Global Wind Oscillation (GWO). While the intent of the legacy GSDM is to extend current thinking beyond the MJO, the GWO quantifies variations used to derive the original GSDM in a manner that is “user friendly” analogous to the WH (2004) “convention”. In addition, the GWO plot does not have the ENSO signal removed.

Please see the revised description of the GSDM per above link -- which will be revised again (work in progress)!!!. Also, I encourage the readers to study the annotated MJO and GWO phase space plots to help relate the global variations explained by those techniques to “weather”.

Links to CPC and PSD ENSO discussions:

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml

http://ds.data.jma.go.jp/tcc/tcc/products/clisys/index.html

The following is a link to information about the stratosphere and other nice monitoring tools:

The following is a link to NCEP model verifications (surf around for lots more)

http://www.cpc.ncep.noaa.gov/schemm/z500ac_wk2_na.html .

The following is a link discussing recent global weather and related events.

http://www.wmo.ch/pages/mediacentre/news/index_en.html

These are probabilistic statements, and work is ongoing to quantify in future posts (for example, risk assessment maps, signal to noise ratio plots and shifts of probability). We hope that an opportunity will arise for us (soon) to have a dedicated web page effort to expedite more objectively, with rigor, thoroughness and verification. This web page effort would hopefully include an objective predictive scheme for the GWO, including hindcasts.