MJO, then El-Nino, or/then What?

Global tropical SSTs still remain above average, with the greatest anomalies across the Indo-Pacific region especially from the central equatorial Pacific to the west coast of South America. Magnitudes across the latter are ~plus 1-3C and extend to ~125m deep (up to 5C) per latest TAO buoy data. It appears that the oceanic Kelvin wave initiated around October 1st is about to reach the South American coast.

The warm-cool-warm SST distribution observed for the past several months has nearly disappeared suggesting our warm event may have already peaked (at least for this cold season). In any case, actual SSTs 29C (threshold for supporting sustained tropical convection) and higher extend from the South Pacific into eastern Indonesia and over portions of the Indian Ocean.

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

Please also see the following CPC link (and others therein) for further ENSO, etc., insights, and remember that official USA information on anything related to ENSO comes from CPC.

http://www.cpc.ncep.noaa.gov/products/predictions/90day/

Since my last posting about a week ago, the most important development in the global weather-climate system has been the evolution of a coherent eastward propagating convectively coupled mode from the Indian Ocean into Indonesia. Per full disk satellite imagery the centroid of this feature was ~0/110E, and was clearly detached from lingering convection across the western Indian Ocean and South Africa (tropical cyclones understood). Interestingly portions of Indonesia that have been convectively suppressed for the last several months are finally getting enhanced rainfall. The Wheeler phase space plot and other tools suggest a strong projection onto a MJO for this eastward moving coupled tropical convective system. My own loose calculations have this MJO moving east ~6-7m/s (5 deg long/day), having speed up a bit during the last few days. I have a concern this MJO may shift into the west central Pacific faster than typically observed.

Forcing from the extratropics has led to yet another separate flare-up ~150-160E over the warm SSTs while the western hemisphere is dynamically suppressed. I do think this MJO will shift into the west central Pacific (while also drifting southward – most numerical and statistical tools agree), possibly consolidating with SST boundary forced convection farther to the east. I suspect we will also see the onset of the Australian monsoon as well as other seasonal cycle behaviors during the next 1-2 weeks. At some point (weeks 3-4?) enhanced convection would be expected to become quite strong around the equatorial date line and South Pacific as the MJO enhances the warm ENSO signal.

The global circulation has responded accordingly including anomalous twin upper tropospheric (baroclinic structures) Indian Ocean anticyclones and down stream west Pacific cyclones. Zonal mean anomalous easterly flow continues across the global tropical atmosphere and global relative AAM is slightly below normal (reanalysis climatology). However, equatorial upper tropospheric westerly wind anomalies (~5-15m/s) are starting to appear over the central and east Pacific. I think we are evolving from GSDM Stage 4 to 1. Complicating things have been the ~15 day central Pacific tropical convective flare-ups and rapid processes across the northern extratropics involving the east-Asian topography (mountain torque term of the global AAM budget).

As the MJO shifts into the west Pacific and eventually enhances the warm ENSO signal, subtropical westerly flow should increase (this process may already be starting per above). Also, as this tropical forcing excites Rossby wave trains which subsequently interact with extratropical baroclinic wave packets, I would expect anticyclonic circulation anomalies to begin dominating the northern polar latitudes and possibly lead to a warming of the stratosphere. In fact, per animations of 150mb daily mean vector wind anomalies, there have already been “bursting anticyclones” across the northern high latitudes for at least the past 1-2 weeks (and stratospheric temperatures have been rising). This would lead to negative phases of things like the AO.

As more models are showing, an evolution from GSDM Stage 1-2 is probable during the next 1-3 weeks. This means after week 1, ridge amplification around 140W into Alaska (linking up with a SSW signal?) may occur during week 2 with a downstream trough in the Rockies (~110W). This pattern would be expected to shift ~10 degrees to the east during week 3. At this time surface temperature anomalies of at least minus 10C are present across much of Alaska, and all that may eventually be forced southward into the western USA. Thus a cold and wet regime for much of the Rockies and Plains may be probable weeks 2-3 which may allow a good snow pack to build across large portions of the country. Afterwards (late January into February), a combined extended anomalously strong North Pacific jet ~30-35N leading to split flow across North America typical of a warm ENSO may be most probable (GSDM Stage 3). That would increase the risk of high impact precipitation events for the USA west coast, particularly California.

Finally, I offer a few comments. The intense tropical convective forcing that we have been observing across the Indian Ocean for the past several months is not typical of a warm ENSO (especially when it dominates over and suppresses the central Pacific). Also, there has been this issue of 2 regions of tropical convective forcing (Indian Ocean and west of date line) since early 2002. I think there a global warming signal (cause is unclear) being communicated to the atmosphere through the anomalously warm tropical SSTs. We have also been seeing lots of forcing-response-feedback scenarios involving the global oceans and atmosphere for the past several years which have been difficult to understand let alone predict. The point is there have been more GSDM “Stage 4-like” responses observed, and I suspect going into the February-April 2007 period we may see more occurrences Stages "4-1" global circulation behaviors.

Appendix

The following is a link to our recently accepted paper by MWR which discusses the GSDM (Weickmann and Berry 2006, in press).

http://www.cdc.noaa.gov/MJO/Predictions/wb2006.pdf

Also, our latest weather-climate discussion was posted on November 29th at

http://www.cdc.noaa.gov/people/klaus.weickmann/disc112006/weather_climate_disco_01_December_2006b.html

In the beginning of Section 2 of that report we give a summary description of the Global-Synoptic-Dynamic Model (GSDM) of subseasonal variability.

I hope to get an update out by late next week. As stated previously, while I am at ESRL/PSD (starting 1/8/07) we hope to post at least short writings on this Blog every other day in support of the Hydrometeorological Testbed Project (HMT -- please see

http://www.esrl.noaa.gov/psd/programs/2007/hmt/).

Ed Berry

A Circulation Response Looms

Global tropical SSTs generally remain above average, with the greatest anomalies across the Indo-Pacific region especially from the central equatorial Pacific to the west coast of South America. Magnitudes across the latter are ~plus 1-3C and extend to 125m deep (up to 5C) per latest TAO buoy data as part of the warm ENSO signal. Interestingly, deep cool anomalies ~1-2C are appearing west of the date line and the 20C isotherm depth has shoaled to about 150W. The warm-cool-warm SST distribution observed for the past several months has become less distinct suggesting our warm event may have already peaked. In any case, actual SSTs 29C (threshold for supporting sustained tropical convection) and higher extend from the South Pacific into eastern Indonesia and over portions of the Indian Ocean.

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

Please also see the following CPC link (and others therein) for further ENSO, etc., insights, and remember that official USA information on anything related to ENSO comes from CPC.

http://www.cpc.ncep.noaa.gov/products/predictions/90day/

Tropical convective forcing remains very complicated. Per full disk satellite imagery and monitoring tools (such as coherent modes and velocity potential Hovmollers) a relatively fast dynamical signal (~15-20m/s) that was moving east through the Western Hemisphere has emerged into Africa and the Indian Ocean. An intense region of deep convection (3-day OLRA less than minus 70W/m**2) has resulted across the equatorial Indian Ocean centered ~70E (including TC Bondo across the South Indian Ocean) and is projecting onto a MJO per Wheeler phase plot. SST boundary forcing and Southern Hemisphere frontal activity has allowed another burst of convection to persist ~0/160E while diurnal activity still continues across the Amazons of northern South America.

To sum up, we continue to see two primary regions of active forcing, Indian Ocean and west of the date line (suppression in between), being modulated by at least MJO-like variations, Kelvin waves and flare-ups with time scales varying anywhere from 5-35 days. The pattern of the 2 regions of active forcing has loosely been drifting east since October (~ 30deg), particularly the Indian Ocean enhancement-Indonesian suppression portion. The Indian Ocean has tended to dominate the central Pacific forcing, and all of these kinds of behaviors are not consistent with the composite tropical convective response to a developing warm ENSO.

A response to the multiple regions of tropical forcing has been for zonal mean easterly wind anomalies to increase throughout much of the equatorial atmosphere since roughly the start of this month (magnitudes approaching 10m/s at 200mb starting about December 13th). Anomalous twin upper tropospheric anticyclones located around 60E, 180 and 60W (per 150mb 12/19/06 daily mean vector wind anomalies) are supporting these easterlies and are also part of the tropical-extratropical circulation response. These easterlies are beginning to propagate poleward off the equator while zonal mean westerly wind anomalies remain across the subtropical and midlatitude atmospheres. Based on the ESRL/PSD reanalysis data AAM plots, as of December 16th the global tendency had reached about minus 15 Hadleys with contributions not only from the equatorial zonal mean easterlies but also weakly from the global mountain and frictional torques (see plots for details). I think GSDM Stage 4 best describes the current weather-climate situation.

My thoughts remain that sometime during weeks 2-3, going along with the seasonal cycle, a consolidation of the tropical forcing may occur centered ~150-160E as it shifts south. Heading into the first week of January we may see a large region of strong tropical thunderstorm activity extend from the South Pacific to just east of Indonesia. This may maintain an increased risk for tropical cyclones across the South Indian Ocean as well as the South Pacific to the east coast of Australia. Afterwards, this whole region may shift southeast along the SPCZ while the ITCZ and much of Brasil are active. I would also expect to the Indian Ocean and Indonesia to remain periodically active. In fact, at some point, say February-March, much of the East Indian Ocean and Indonesia may become quite active while the central Pacific starts to shut down. What is left of the dynamical warm ENSO signal may be centered near the Americas.

I think we are transitioning to GSDM Stage 1 as I type. Uncertainty for any predictive insight remains extremely high. However, after Christmas heading into the first couple of weeks in January 2007, I would almost be surprised if a GSDM Stage 2 situation did not evolve. That would suggest ridge amplification just off the North American west coast into Alaska with a few digging synoptic troughs across the Rockies and Plains. Ramifications would include true Arctic air penetrating into the lower 48 states with lots of wintery precipitation to go along with it, especially for the eastern 2/3rds of the country. The Pacific Northwest may still see bouts of precipitation as the troughs come inland. Afterwards the DREADED extended combined jet from Asia to the west coast of North America (with split flow across the continent) may appear which is typical of GSDM Stage 3 that is most probable during a mature global response to a warm ENSO. At that point the precipitation emphasis would be along the USA west coast as well as the Deep South. While the latter may verify for a January-March seasonal mean, I could see the February-March period going back to GSDM Stages 4-1.

Appendix

The following is a link to our recently accepted paper by MWR which discusses the GSDM (Weickmann and Berry 2006, in press).

http://www.cdc.noaa.gov/MJO/Predictions/wb2006.pdf

Also, our latest weather-climate discussion was posted on November 29th at

http://www.cdc.noaa.gov/people/klaus.weickmann/disc112006/weather_climate_disco_01_December_2006b.html

In the beginning of Section 2 of that report we give a summary description of the Global-Synoptic-Dynamic Model (GSDM) of subseasonal variability. I hope to get an update out by late next week. As stated previously, while I am at ESRL/PSD we hope to post at least short writings on this Blog every other day in support of the Hydrometeorological Testbed Project (HMT -- please see

http://www.esrl.noaa.gov/psd/programs/2007/hmt/).

Ed Berry

Only a Matter of Time? Will There be Winter?

Global tropical SSTs generally remain above average. The greatest anomalies are across the Indo-Pacific region with magnitudes ~plus 1-3C especially along the equatorial cold tongue. The latter is associated with the basin wide warm ENSO, with the warm anomalies (up to 5C) extending to 150m deep per latest TAO buoy data. Interestingly, deep cool anomalies ~1-2C are appearing west of the date line and the 20C isotherm depth has shoaled to about 160W. Also, the warm-cool-warm SST distribution has become less distinct during the past several weeks. Perhaps our warm event may have already peaked. In any case, actual SSTs 29C and higher extend from the South Pacific into eastern Indonesia and over portions of the Indian Ocean.

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

Please also see the following CPC link (and others therein) for further ENSO, etc., insights, and remember that official USA information on anything related to ENSO comes from CPC.

http://www.cpc.ncep.noaa.gov/products/predictions/90day/

Tropical convective forcing remains very complicated. Per full disk satellite imagery and monitoring tools (such as coherent modes and velocity potential Hovmollers) relatively fast dynamical signals moving through the Western Hemisphere are starting to emerge into Africa and the Indian Ocean. A fairly intense flare-up has occurred ~0/60E during the last week and may be evolving into a weak MJO per Wheeler phase plot. SST boundary forcing and Southern Hemisphere frontal activity has allowed another intense burst of convection to occur ~0/160E while intense diurnal activity persists across the Amazons of northern South America. At least 2 and arguably 3 significant regions (counting South America) of tropical forcing are impacting the extratropics. In fact, extratropical responses and feedbacks linked to some of this activity may have contributed to recent very poor week-2 500mb ACC skill scores for the NCEP GFS ensemble mean for North America (less than minus 0.3). Since early October the enhanced-suppressed-enhanced distribution of tropical forcing across the Indo-Pacific region has shifted roughly 40 degrees to the east, which may reflect a slow ENSO signal.

Zonal mean easterly wind anomalies have been increasing throughout the equatorial and particularly northern subtropical atmospheres since about the start of this month (~5-10m/s at 200mb). Anomalous zonal mean westerly flow flanks these easterlies suggestive of subtropical jets across both hemispheres. GSDM Stage 4 best describes the current weather climate situation (not all AAM plots from ESRL/PSD are available). Where we go from here remains very unclear. As I have offered before, my thoughts are to expect some consolidation of the tropical forcing from the west central into the South Pacific going into January 2007 (as it shifts south).

Nearly all the numerical models are suggesting closed low development across the Desert Southwest by early next week to then eject northeast affecting much of the country. Thus while winter storm conditions are probable from the central Rockies into the portions of the Plains, the Deep South may receive heavy rainfall along with severe local storms. True Arctic air will be lacking with this system.

After Christmas heading into the first couple of weeks in January 2007, I would almost be surprised if a robust GSDM Stage 2 situation did not evolve (bypassing Stage 1). That would mean ridge amplification just off the North American west coast into Alaska with a few digging synoptic troughs across the Rockies and Plains. Ramifications would include true Arctic air penetrating into the lower 48 states with lots of wintery precipitation to go along with it, especially for the eastern 2/3rds of the country. Afterwards the DREADED extended combined jet from Asia to the west coast of North America (with split flow across the continent) may appear which is typical of GSDM Stage 3 that is most probable during a mature global response to a warm ENSO.

Appendix

The following is a link to our recently accepted paper by MWR which discusses the GSDM (Weickmann and Berry 2006, in press).

http://www.cdc.noaa.gov/MJO/Predictions/wb2006.pdf

Also, our latest weather-climate discussion was posted on November 29th at

http://www.cdc.noaa.gov/people/klaus.weickmann/disc112006/weather_climate_disco_01_December_2006b.html

In the beginning of Section 2 of that report we give a summary description of the Global-Synoptic-Dynamic Model (GSDM) of subseasonal variability.

I will try to do at least a short posting next week. As stated previously, while I am at ESRL/PSD we hope to post at least short writings on this Blog every other day in support of the Hydrometeorological Testbed Project (HMT -- please see

http://www.esrl.noaa.gov/psd/programs/2007/hmt/).

Ed Berry

Update

Because of my travel to the STISS (THORPEX) in Germany from 12/1-12/8, I will not be able to do a writing until the following week at the earliest. However, Klaus and I did post another weather-climate discussion on the ESRL/PSD MJO web page at


http://www.cdc.noaa.gov/people/klaus.weickmann/disc112006/weather_climate_disco_01_December_2006b.html


Predictive insights are offerred in Section 2. Also, since I am involved with the Hydrometeorological Testbed project (HMT), I will be at ESRL/PSD during approximately January and March 2007 (~1 month each). During those times we plan on short postings to this blog at least every other day. By then we will know if we get GSDM Stage 3 or "something else". Right now uncertainty remains tremendously high.

Ed Berry

New World Atmosphere Winter Before El-Nino???

Please see past postings for web site links. In this writing I am going to post a version of a draft of Section 2 (Predictive Insights) which will appear in our next weather-climate discussion for the ESRL/PSD MJO web site.

Global tropical SSTs remain well above average across the Indian Ocean (IO) and from around the date line to the west coast of South America, with weekly mean magnitudes of 1-3C along the equatorial cold tongue. Warmth also persists across the North Atlantic, particularly from the Caribbean to the west coast of Africa. At depth the positive anomalies along the equatorial east Pacific extend to about 250m with values to around 5C at 125m at 120W meaning a deeper than normal thermocline assisted by the Kelvin wave currently propagating eastward along it. Anomalies south of Indonesia remain slighly below average while their spatial distribution decreases. During the past week equatorial SST tendencies have generally been positive with magnitudes ~.5-1.0C. Part of this SST distribution is from a well defined and currently strengthening warm phase of ENSO.

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

Please also see the following CPC link (and others therein) for further ENSO, etc., insights, and remember that official USA information on anything related to ENSO comes from CPC.

http://www.cpc.ncep.noaa.gov/products/predictions/90day/

Per full disk satellite imagery two prominent areas of tropical convective forcing are evident. One is located over the warm SSTs around the equatorial date line with the other larger region centered on the IO (including central and southern Africa), with latest 3-day averaged OLRA ~minus 70-90 W/m**2. The recent Western Hemisphere tropical forcing linked to a convectively coupled Kelvin wave has lost coherence. From animations such as 150mb and 250mb daily mean vector wind anomalies, the IO forcing appears to be organizing into an MJO. There is now the quadrapole of upstream twin subtropical anticyclones (and low level westerlies) with downstream cyclonic anomalies, and these features are interacting with the extratropics through wave energy dispersion processes. In fact, the latest plot on the Wheeler diagram shows a projection well above 1 sigma and there is also a projection onto the coherent modes Hovmollers. Finally, a loose phase speed computation has a movement of roughly 5m/s or about 20 deg of longitude during a 5-day period from November 15-20.

The extratropics have been strongly impacted by this complex tropical forcing, with subsequent feedbacks. Since late October zonal mean westerly wind anomalies (~5-15m/s at 200mb) have propagated from the tropical into the subtropical atmospheres (to ~25-30N) while being replaced by easterlies. During early November an anomalous combined jet did extend across the North PacificOcean ~35N meaning a GSDM Stage 3 situation was briefly present, and this was about the time excessive rainfall across the Pacific Northwest commenced. Some of this westerly flow did make it to the surface augmenting deep tropical moisture transport from the date line region to the northwestern USA. Additionally, upper tropospheric divergent outflows from the African and IO convection through interactions with baroclinic wave packets led to the current blocking structure near Kamchatka. Per animations of 150mb and 250mb daily mean vector wind anomalies from ESRL/PSD, feedbacks from this blocking assisted with the dynamic suppression of convection along and to the north of the equatorial date line (where SSTs are warm) until about a week ago.

Careful examination of the animations shows that a recent Rossby wave energy dispersion linked to the MJO arcing into the Southern Hemisphere extratropics contributed to the flare-up of the South Pacific tropical convection. This region of forcing has been expanding back to the west-northwest into northern Indonesia during the last few days. Moreover, convectively coupled Kelvin waves emanating from the MJO along with the expanding date line/South Pacific convection have allowed some filling in to occur meaning a band of tropical thunderstorm clusters across northern Indonesia linking the 2 regions. Twin upper tropospheric anticyclones supporting cross equatorial flow from the Southern Hemisphere are also present around the date line. The latter are supporting the linkage of a subtropical jet with the trough currently moving into the western USA.

Global relative AAM is about 1 sigma below the 1968-1997 reanalysis data climatology as of November 20th. Contributions to this low AAM are coming from the zonal mean easterly anomalies across the deep tropics and the Southern Hemisphere subtropical atmosphere as well as ~40N. The latter can be linked to the recent blocking episodes from Greenland to Kamchatka. Global relative AAM tendency reached a negative minimum of ~minus 20 Hadleys around November 16th only to be approaching plus 20 Hadleys on the 20th. Positive zonal mean tendencies of around 2 Hadleys were appearing from the equator to around 20N with weakly negative values across the Arctic (latest AAM plots here), with the former believed to be linked with South Pacific tropical convective flare-up discussed above. The contributions of the mountain and frictional torques to the global AAM budget were ~plus 10-15 Hadleys each. However, there were significant zonal mean variations. For instance, the mountain torque had magnitudes of ~2 Hadleys and a minus-plus-minus distribution from 30-90N.

GSDM Stage 4 has best described the weather-climate situation for roughly the past couple of weeks. However, given the MJO signal, careful interpretation of the AAM plots and critical daily monitoring, a transition to GSDM Stage 1 may be in progress. For instance, animations do show the recent Kamchatka blocking becoming "dislodged"and is tied to a Rossby wave energy dispersion from the IO convection. As shown by most models (but with large differences in the details) the trough which has been present across the Gulf of Alaska is about to deepen into the western USA (leading to a greater projection onto the negative phase of the PNA). Arctic air has been building up across Alaska and northwest Canada for the last several weeks, and this trough will have that airmass as a cold air source. The latter has been discussed as a possibility in previous postings.

However, where we go from here remains tremendously uncertain, especially given the seasonal cycle (and other issues such as high latitude blocking). There are also going to be impacts from tropical convective flare-ups until if and when "El-Nino kicks in". For instance, the positive AAM tendency we are now seeing I think is directly attributable to the current "MJO forced flare-up". A probable thought may be for MJO forcing to consolidate with the date line thunderstorm clusters leading to a large region of intense tropical rainfall extending from near the Philippines to the South Pacific centered ~150E by late week 2 or week 3. This region may then stall before shifting east-southeast toward the central Pacific/SPCZ by early January 2007. Thus perhaps GSDM Stage 1 with subtropical jets may be the case for the weather-climate situation through week 2, followed by GSDM Stage 2 for much of (mid-late?) December. Afterwards, GSDM Stage 3 may appear, which is "typical" during the warm phase of ENSO. In the USA outlooks that follow, confidence is below average for week 1, then as low as it gets for weeks 2-3.

Week 1 (24-30 November 2006): GSDM Stage 1 with a moist subtropical jet is most probable. This situation generally favors an active weather regime for the Rockies and Plains, with a southwest-northeast storm track across the central USA. An important issue is how soon deep tropical moisture transport through the Gulf of Mexico can resume after the recent surges of cool dry air. Latest observations suggest low level moistening is occurring across the Gulf of Mexico. Most models do predict baroclinic development on the Plains by around the middle of next week, but with still serious phase and amplitude issues. They are "catching-up" to the changing tropical convective forcing and other processes. A thought to offer would be a slower and more amplified solution for trough development, and the models are now trending there. In any case, bitterly cold Arctic air is likely to penetrate into the Rockies and Plains by the end of this period while the Deep South warms up. Depending on the details, portions of the Rockies and Plains may have severe winter weather conditions while severe local storms become a concern for the locations such as the south central states to the Ohio Valley.

I also want to make special mention of the still on-going tropical cyclone risks across the central Pacific and possibly other regions. Satellite pictures show evidence of development trying to occur west-northwest of the equatorial date line. Locations such as the Philippines may be impacted later this period. Tropical cyclone Yani is already in progress across the South Pacific islands, and more development may follow. Finally, locations across the Indian Ocean may become at risk for tropical cyclone development as the MJO slowly moves east.

Week 2 (1 - 7 December 2006): Same as week 1, but with the usual synoptic variations in amplitude. Perhaps another episode of baroclinic development across the Rockies and Plains may occur toward the end of this period. I do not think the week 1 storm system will be the "last western/central USA" trough. In fact, the stronger and slower moving troughs may not be until the last half of December, particularly if a transition from GSDM Stage 1-2 occurs.

Week 3 (8 -14 December 2006): See week 2. We may have a period during weeks 4-6 of extremely cold air covering particularly the central USA should a mature GSDM Stage 2 evolve. That may allow a snow pack to build across locations such as the Upper Mississippi Valley and Great Lakes. Given the magnitude of our warm ENSO (and other factors) I would be surprised not to see an anomalously strong combined jet ~30-35N extend from East Asia into the western USA (with split flow across North America) by ~ the middle of January 2007, which would be GSDM Stage 3. This would significantly increased the probability of high impact weather (heavy precipitation, high winds, etc.) for the USA west coast perhaps affecting California the most (other regions for hazards and weather understood).

Appendix

The following is a link to our recently accepted paper by MWR which discusses the GSDM (Weickmann and Berry 2006, in press).

http://www.cdc.noaa.gov/MJO/Predictions/wb2006.pdf

From taking into consideration the interactions of 4 different subseasonal time scales, a sequence of maps 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 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. Our latest weather-climate discussion dated August 18th, 2006 (and updated September 9th), has been posted on the ESRL/PSD MJO web site at

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

I will try to do another posting before my trip to the STISS (THORPEX) in Germany.

Ed Berry

The Fist of El-Nino Continues (The Devil of the Tropics???)

Please see past postings for web site links. Also, I need to get very serious about paring down the length. Hopefully that will eventually translate to more frequent but short discussions

The overall spatial distribution of global tropical SSTS still has warm anomalies across the Indian Ocean (IO) and central/eastern tropical Pacific (~plus 1-3C) with cool (but weakening) values across southern Indonesia. Warm anomalies also persist across the Atlantic. Actual SSTS of 30C and higher remain present around the date line with 29C and warmer across the Indian Ocean. The positive SST anomalies along the equatorial cold tongue extend to depths of roughly 150m with magnitudes ~plus 4C meaning a deeper than normal thermocline. Part of this SST distribution is from a well defined warm ENSO signal although there are other contributions.

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

Please also see the following CPC link (and others therein) for further ENSO, etc., insights, and remember that official USA information on anything related to ENSO comes from CPC.

http://www.cpc.ncep.noaa.gov/products/predictions/90day/

Loosely 3 regions of tropical convective forcing are present. Per full disk satellite imagery (and other monitoring tools) these areas are centered on the Americas, from Africa into the Indian Ocean and finally across the Southwest Pacific between the Polynesian Islands and Australia. There are indications the convection across the Indian Ocean may be evolving into a coherent eastward propagating feature, possibly an MJO. The tropical forcing across the South Pacific has shown a rapid increase during the last couple of days, likely a response to the warm SSTs (and interactions with the southern extratropics). The latter appears to be shifting to the west-northwest along the South Pacific Convergence Zone (SPCZ). The signal across the Western Hemisphere is at least partly a convectively coupled Kelvin wave.

The extratropics have been strongly impacted by this complex tropical forcing, with subsequent feedbacks. For instance, since late October zonal mean westerly wind anomalies (~5-15m/s at 200mb) have propagated from the tropical into the subtropical atmospheres (to ~30N) while being replaced by easterlies. Some of this poleward propagating westerly flow has made it to the surface (ex., the North Pacific Ocean) augmenting deep tropical moisture transport from the date line region to the USA Pacific Northwest where excessive rainfall has been occurring. Additionally, upper tropospheric divergent outflows from the African and Indian Ocean convection through interactions with baroclinic wave packets have led to the current blocking structure near Kamchatka. Per animations of 150mb and 250mb daily mean vector wind anomalies from ESRL/PSD, feedbacks from this blocking have assisted with the recent dynamic suppression of convection along and to the north of the equatorial date line (where SSTs are warm).

GSDM Stage 4 best describes the current weather-climate situation. Where we go from here remains very uncertain. Yesterday I thought a slow transition from GSDM Stage 4-1 was most probable during the next 1-3 weeks. However, I am now concerned about the recent very rapid increase of convection across the South Pacific (daily monitoring is critical!). Respect needs to be given to the warm SSTs in that region. My own thought would be to “expect” a convectively coupled feature to shift east from the Indian Ocean into the west central Pacific during the next 1-3 weeks, possibly consolidating with a convectively coupled Rossby wave around ~120-140E north of the equator. The latter may evolve from the South Pacific.

Thus I think GSDM Stage 1 is probable by week 2, but may give way to Stage 2 by/during early December. One option with this scenario would be for an eastward shift of existing circulation anomalies, meaning full latitude troughs with Arctic air to impact the western USA sometime during week 2. By week 3 these troughs may shift toward the Plains while a ridge amplifies off the North American coast into Alaska. This would suggest an active regime for the Plains (all impacts should be understood) week 2 followed by perhaps much colder than normal temperatures for much of the country starting early December (centered on the Plains/Upper Mississippi Valley). Locations such as the Pacific Northwest may get a break from excessive precipitation by that time. We will see what happens; including if/when GSDM Stage 3 makes its appearance (extended low latitude North Pacific combined jet with split flow across North America – “typical” of a warm ENSO).

Work is on-going to write another weather-climate discussion for the ESRL/PSD MJO web page. Since it would be ideal to have this discussion posted before attending the 4-8 December 2006 THORPEX meeting in Germany, it will be difficult for me to do these postings weekly. Please keep checking, and see the Appendix.

Appendix

The following is a link to our recently accepted paper by MWR which discusses the GSDM (Weickmann and Berry 2006, in press).

http://www.cdc.noaa.gov/MJO/Predictions/wb2006.pdf

From taking into consideration the interactions of 4 different subseasonal time scales, a sequence of maps 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 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. Our latest weather-climate discussion dated August 18th, 2006 (and updated September 9th), has been posted on the ESRL/PSD MJO web site at

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

Ed Berry

War Resumes Between Good and Evil

Please see past postings for web site links. Also, I need to get very serious about paring down the length. Hopefully that will translate to more frequent but short discussions.

The spatial distribution of global tropical SST anomalies has not changed significantly during the past week or so, still resembling a mature warm event. Positive anomalies remain across the western Indian Ocean and along the equator from ~date line-South America with cool readings around Indonesia particularly south of the equator (see November 3rd posting for details). The warmest SSTs are still found along the equatorial date line with readings near 31C having ~2C anomalies. Equatorial SST and SST anomaly tendencies over the last week were ~minus 0.5-1.0C from around 140E-South America with some positive values across the Indian Ocean. Additionally, SST animations suggest there has been about a 10 degree eastward shift of the warm-cool-warm pattern discussed above during the last 2-3 months (seasonal cycle understood).

What is also interesting is the above average SSTs across the extratropical North Pacific Ocean basin. Granted, the latter have a secondary role to tropical SSTs (and different ocean-atmosphere dynamical processes – I need to keep down the length!). However, warm North Pacific SSTs is not consistent with a warm ENSO (in the composite sense), again keeping in mind the seasonal cycle. The latter could quickly change should GSDM Stage 3 evolve meaning a strong North Pacific jet with attendant East Asian cold air surges, etc., (which does not look probable for at least the next few weeks).

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

Please also see the following CPC link (and others therein) for further ENSO, etc., insights, and remember that official USA information on anything related to ENSO comes from CPC.

http://www.cpc.ncep.noaa.gov/products/predictions/90day/

The point I want to emphasize in this writing is our two regions of tropical convective forcing is back. One region extends from equatorial Africa into the central Indian Ocean with the other centered ~0/160E. Yes, there are those who will invoke the Indian Ocean Dipole (IOD) notions and offer this situation is not all that unusual for a warm ENSO. While there is truth to these concepts, from my monitoring of trying to understand the dynamics of ocean-atmosphere forcing-response-feedbacks involving many scales of motion making use of the GSDM framework, the current weather-climate situation is much more complicated. From looking at animations of daily mean 150mb and 250mb vector wind anomalies I can clearly see the extratropics interacting with both regions of tropical forcing while helping to maintain them. We need to also remember this current warm ENSO evolved in a very random (and unpredictable) manner.

There is evidence from various tools (ex., Hovmoller plots of 250mb meridional wind anomalies in the 10-40N/S latitude bands) that subtropical wave trains are currently present in both hemispheres. I also have a suspicion that the tropical forcing over Africa into the Indian Ocean is trying to evolve into another MJO (the Wheeler phase space plot supports this). We will see. Global relative AAM tendency as of November 6th was ~minus 20 Hadleys as zonal mean westerly wind anomalies propagate poleward to ~30N/S while being replaced by zonal mean easterly wind anomalies throughout the deep tropics (magnitudes ~5-15m/s at 200mb). GSDM Stage 4 still best describes our current weather-climate situation, and may go into Stage 1 during the next 1-3 weeks. Again, forecast uncertainty is about as high as it can get.

As we progress into the upcoming boreal winter, to me it will be interesting to watch how far east the above discussed SST anomaly pattern progresses. I do think there will continue to be 2 regions of tropical forcing (on average). We may also observe a fair frequency of GSDM Stages 4-1 as opposed to a persistent GSDM Stage 2-3 during January-February. Whatever the case, while a “simple” seasonal mean (DJF, for example) pattern of temperature and precipitation anomalies may emerge which many might attribute to warm ENSO, the variability may be anything but simple with a great deal of global high impact weather with contributions coming from other complex processes not well understood (which is one reason why no 2 warm and cold events are alike beyond the composite/statistical senses).

To summarize, I think we have 1) a warm event (plus a global warming signal, with cause still unclear(?)), 2) an increasing role of the Indian Ocean SSTs, 3) the possibility of a re-emerging MJO signal, 4) 20-30 day tropical convective variability (not discussed), 5) some evidence of mountain-frictional torque index cycle variations (also not discussed – may be linked to (4)), fast RWDs, baroclinic wave packets and all sorts of other white noise, 6) increasing blocking at the higher latitudes which I can link to both regions of tropical forcing and 7) the always present seasonal cycle issues.

Amplification is occurring throughout much of the subtropics and extratropics from Asia-North America as I type. A residual of the once extended strong North Pacific jet (anomalies are ~30-40m/s ~40N east of the date line at 250mb) is likely to penetrate into much of the country during week 1. The models do show this; however, it is still unclear where and when any amplifying trough will occur. There is likely to be high impact weather for at least the Pacific Northwest (heavy rain) and Deep South/Ohio Valley (severe local storms, etc.) , and perhaps the Upper Mississippi Valley and Great Lakes for winter weather. Disciplined monitoring will be needed including the models as they “catch on”.

During weeks 2-3 a more “classic” GSDM Stage 1 (with subtropical jets) may be probable particularly if at least a “MJO-like” feature develops. That would be favorable for full-latitude troughs to penetrate into western North America having an Arctic cold air source. We should all know “what that means” by now.

Work is on-going to write another weather-climate discussion for the ESRL/PSD MJO web page. Since it would be ideal to have this discussion posted before attending the 4-8 December 2006 THORPEX meeting in Germany, it will be difficult for me to do these postings weekly. Please keep checking, and see the Appendix.

Appendix

The following is a link to our recently accepted paper by MWR which discusses the GSDM (Weickmann and Berry 2006, in press).

http://www.cdc.noaa.gov/MJO/Predictions/wb2006.pdf

From taking into consideration the interactions of 4 different subseasonal time scales, a sequence of maps 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 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. Our latest weather-climate discussion dated August 18th, 2006 (and updated September 9th), has been posted on the ESRL/PSD MJO web site at

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

Ed Berry

SST Axis of Evil Continues

Please see past postings for web site links. I am going to discontinue inserting most of them in an effort for brevity. I also need to do the same with these postings.

The spatial distribution of global tropical SST anomalies has not changed significantly during the past week or so, still resembling a mature warm event. Positive anomalies remain across the western Indian Ocean and along the equator from ~170E-South America with cool readings around Indonesia particularly south of the equator. There has been some warming of SSTs around Indonesia into the Bay of Bengal and Arabian Sea extending to just southeast of Asia, as well as northwest of Australia, with positive tendencies ~0.5-1.0C during the past week. The latter may be a direct result of solar input due to the strong convective suppression present there.

SST anomaly magnitudes as low as ~minus 2C remain just south of Indonesia on 3 November while ~plus 2C were observed just east of the equatorial date line and west of South America (keep in mind the seasonal cycle of SSTs). These positive SST anomalies are deep with plus 4C and greater observed at ~150m/165W per five-day averaged TAO buoy data ending 3 November. A recent surface westerly wind burst linked to the last MJO event appears to have initiated a down welling oceanic Kelvin wave currently approaching 160W along the equator.

The SST horse shoe pattern of cool surrounding warm anomalies (would be reversed for a cold event) across the tropical Indo-Pacific remains (axes of SST anomalies), and is best defined across the Southern Hemisphere with values ~minus 1-2C. Interestingly, there is anomalous SST warmth emanating from the Indian Ocean encasing the cool anomalies across both hemispheres including the extratropics.

Overall, the spatial coverage of above average global SSTs (tropics and extratropics) exceeds those which are cooler than normal. Much of the midlatitude South Pacific Ocean has below normal SSTs as a response to cooling from an intense baroclinic storm track since at least May 2006. It is my feeling that anomalous surface cross equatorial cool southerly flow from the deep southern extratropics into Indonesia starting around May 2006 linked to this storm track activity played a critical role to the evolution of our stochastically forced warm event. Please remember that in the tropics the SSTs generally force the atmosphere with the opposite for the extratropics (yes, everything understood).

SSTs of 30C and warmer cover much of the equatorial date line region while ~29-29.5C waters are present across the central Indian Ocean and around both sides of Central America. Weak positive SST anomalies cover most of the tropical Atlantic with actual temperatures ~28-29C. The warm ENSO conditions are here to stay for at least the next 3-6 months. It is now a matter of how the spatial patterns of the SSTs evolve, and no two warm events (or anything else that occurs in the coupled global ocean-atmosphere, etc. system) are alike. The predictability of these kinds of details on the seasonal time scale is noise, as are the weather impacts.

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

Please also see the following CPC link (and others therein) for further ENSO, etc., insights, and remember that official USA information on anything related to ENSO comes from CPC.

http://www.cpc.ncep.noaa.gov/products/predictions/90day/

The dynamical signal with the MJO is all but gone. Per full disk satellite imagery and other tools enhanced tropical convective forcing remains most intense around 0/160E (OLRA~ minus 90W/m**2), with two other regions from Africa into the central Indian Ocean and the last from the Amazons and SACZ into the Atlantic ITCZ. The convection across the west central Pacific has been shifting west during the last week, weakly projecting onto a convectively coupled Rossby mode. Some consolidation of forcing is possible during the next couple of weeks north of Indonesia, and particular attention will need to be paid from the Bay of Bengal to the Philippines should this occur.

In general, as has been true since ~2002, it appears probable that we may have to deal with 2 regions of tropical convective forcing (and a weak, if any, MJO signal) again for this upcoming boreal winter, with the warm ENSO signal possibly dominating. I would expect to see coherent tropical convective forcing evolve and propagate east, but perhaps much faster than MJOs (Kelvin waves), and maybe other “MJO-like” behaviors (see our weather-climate discussions). Is the latter the result of a longer term trend such as global warming (what I termed as a “new world atmosphere” in past postings)?

Since about Halloween, tied to the past MJO, there has been fairly coherent poleward propagation of zonal mean zonal westerly wind anomalies with magnitudes up to 15m/s ~35N at 200mb during the past couple of days. Zonal mean upper tropospheric easterly wind anomalies have become dominate within 10 degrees of the equator during the past week (and also from ~45-60N). Global relative AAM has become slightly negative (~minus .5 sigma per operational data), with much of that coming from the global mountain torque of ~minus 15 Hadleys. I can attribute some of this as the result of anomalously low mean sea level pressures along the east slopes of north-south mountain ranges for both the tropics and extratropics impacted by the poleward propagation of the zonal mean anomalous westerlies discussed above. The reason is not only have these westerlies been propagating poleward, but also downward through the troposphere, eventually reaching the surface. There have also been complex interactions with much faster time scales such as the mid-latitude eddies that have subsequently impacted the tropical convection (which has also contributed to recent lowering of mean sea level pressures across the deep tropics).

In terms of the tropical forcing and AAM budget, GSDM Stage 4 may best describe the current situation. However, as shown by the ESRL/PSD animations of both 150mb and 250mb daily mean vector wind anomalies, with magnitudes of roughly 15-30m/s, twin tropical/subtropical cyclones cover much of the Indian Ocean while anticyclones rule over the central Pacific centered around the date line. Centered ~40N, a large anomalous cyclonic gyre covers much of the North Pacific Ocean basin supporting enhanced westerlies ~30-35N (consistent with the poleward propagation discussed above). In fact, a weekly average of 150mb vector wind anomalies ending 4 November suggests a coherent residual of Rossby wave energy dispersion linked to the west central Pacific tropical forcing arcing to a blocking pattern across the North Atlantic (which would project onto a reverse NAO and explain some of the current zonal mean anomalous higher latitude easterly flow). Thus in terms of the actual global circulation GSDM Stage 3 may apply (suggesting split flow across North America).

This kind of response can be expected from a warm ENSO, and may be a pre-cursor to the type of circulation pattern for this upcoming boreal winter. For the USA, during the past week we have seen precipitation increase along the west coast from northern California to Alberta (yes, Canada) while much of the rest of the country has turned warmer and dryer. Back to the GSDM, I would offer Stages 3-4 for the current situation.

To summarize, I think we have 1) a warm event (plus a global warming signal whose cause is unclear?), 2) an increasing role of the Indian Ocean SSTs, 3) the MJO signal which has become very weak, 4) 20-30 day tropical convective variability (not discussed), 5) some evidence of mountain-frictional torque index cycle variations (also not discussed – may be linked to (4)), fast RWDs, baroclinic wave packets and all sorts of other white noise, and 6) seasonal cycle issues.

As stated above, we may be seeing an early November rendition of an expanded East Asian Jet (EAJ). There are countless sensitivity issues discussed in past postings and weather-climate discussions. I also did not discuss how our GSDM Stage 3 (like?) circulation may have come about over the past week due to complexity. Short story is that in addition to the tropical forcing discussed above, tied to East Asian baroclinic wave packets, there was also a flare-up if convection around the Philippines (Tropical Northwest Pacific) that led to former Super Typhoon Cimarron. This forcing also added westerly flow. With that convection “gone” and at least some consolidation (see above) by around week 2, I think the North Pacific Jet will retract. This is just one of the sensitivity matters the current numerical models are struggling with in terms of predictions.

During this upcoming week, a split flow pattern should remain across the country. Most of the precipitation looks to occur along the west coast (mainly Pacific Northwest) and eventually across the Deep South. The latter will depend on just how much baroclinic development occurs along the southern westerlies. Whatever the case may be, a cold air source looks to be lacking.

For weeks 2-3, GSDM Stage 1 may evolve, meaning a full latitude trough with an Arctic cold air source (monitoring does show some recent build up – recall where the blocks are) would become increasingly probable for the western half of the country. There may also be an active subtropical jet tied to the warm ENSO. This would be a very active weather regime (including possible high-impact events such as blizzard conditions and severe local storms) for this time of year across a good part of the country (including a southwest flow storm track across the middle). I think the readers are familiar what the weather would be from all this.

Work is on-going to write another weather-climate discussion for the ESRL/PSD MJO web page. Since it would be ideal to have this discussion posted before attending the 4-8 December 2006 THORPEX meeting in Germany, it will be difficult for me to do these postings weekly. Please keep checking, and see the Appendix.

Appendix

The following is a link to our MWR paper that discusses the GSDM (Weickmann and Berry 2006, in press).

http://www.cdc.noaa.gov/MJO/Predictions/wb2006.pdf

From taking into consideration the interactions of 4 different subseasonal time scales, a sequence of maps 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 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.

Our latest weather-climate discussion dated August 18th, 2006 (and updated September 9th), has been posted on the ESRL/PSD MJO web site at

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

Ed Berry

Truce Over With???

Please see past postings for web site links. I am going to discontinue inserting most of them in an effort for brevity. I also need to do the same with these postings.

The spatial distribution of global tropical SST anomalies still resembles a mature warm event, with positive values across the western Indian Ocean and along the equator from ~170E-South America and cool readings around Indonesia particularly south of the equator. Magnitudes as low as ~minus 2C and lower were observed north of Australia on 26 October while ~plus 2C just east of the equatorial date line and west of South America (keep in mind the seasonal cycle of SSTs). The SST horse shoe pattern of cool surrounding warm anomalies (would be reversed for a cold event) across the tropical Indo-Pacific remains, and is best defined across the Southern Hemisphere with values ~minus 1-2C.

SSTs of 30C and warmer cover much of the equatorial date line region while ~29-29.5C waters are present across the central Indian Ocean and around both sides of Central America. Weak positive SST anomalies cover most of the tropical Atlantic with actual temperatures ~28-29C.

There is some evidence that the warm-cool-warm SSTs discussed above have shifted ~10 degrees east during the last week or so. The recent surface westerly wind event (WWE) with anomalies in excess of 10m/s (westerly anomalies still remain along and east of the date line) has apparently excited another oceanic Kelvin wave which is propagating toward the east Pacific. Anomalies as high as plus 4C down ~150m at 170W were observed per recent TAO array buoy data. This oceanic Kelvin wave along with an advective component from the anomalous westerly flow may be helping to shift the SST distribution to the east.

The WWE tied to the recent MJO helped to strengthen our warm ENSO. At this point I see 2 ocean basins with warm SSTs, the central equatorial Indian Ocean and the date line. There are folks that will call the former a positive phase of the Indian Ocean Dipole (IOD) and others which feel this SST distribution is consistent with a warm event (I feel the latter). Whatever the case, I try to understand the weather-climate situation from a dynamical forcing-response-feedback perspective, and I think I can see physically how this whole SST situation evolved starting around March 2006 (too long to discuss here). The point is both of these warm ocean basins (and other oceanic regions) are currently impacting the circulation and will continue to do so.

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

Please also see the following CPC link (and others therein) for further ENSO, etc., insights, and remember that official USA information on anything related to ENSO comes from CPC.

http://www.cpc.ncep.noaa.gov/products/predictions/90day/

Full disk satellite imagery and other monitoring tools (coherent modes Hovmollers, velocity potential/OLRA animations, etc.) suggest the dynamical signal with the MJO has returned to the Eastern Hemisphere and was located ~60E. The phase speed of this signal has slowed considerably and its magnitude has significantly weakened. Tropical convective forcing has been increasing across much of the central Indian Ocean and in a band from the South Pacific toward the Philippines (with Tropical Cyclone Cimaron). Enhanced convection has recently been propagating east-southeast along the South Pacific Convergence Zone (SPCZ) (weakly projecting onto a convectively coupled Kelvin wave) while also shifting back toward the Philippines. In fact, the recent pattern of Indian Ocean enhancement-Indonesian suppression- west Pacific enhancement is less robust than a week ago.

My own thought is we may see some consolidation of the tropical convective forcing ~ 10-15N/90-120E during the next 1-2 weeks (north of the cool SSTs). However, flare-ups across both the Indian Ocean and especially the date line/South Pacific region may occur “any time”. Illustrations of this kind of behavior are the weather-climate events during past 4 weeks or so which we hope to detail in another weather-climate discussion for the ESRL/PSD MJO web page.

Briefly, as the dynamical signal with the MJO interacted with the warm date line SSTs during late September and early October, a Rossby wave energy dispersion (RWD) occurred across the PNA sector leading to a deep trough across the Great Lakes and North Atlantic blocking by around 12-14 October (recall the Buffalo, NY snow event). There were subsequent RWDs from the North Atlantic blocking which interacted with other wave packets moving across Asia. These helped to re-invigorate the date line tropical convection through their enhanced divergent upper tropospheric outflows all while the MJO signal was moving through the Western Hemisphere, by about 15 October. Among other responses, there was a central/east tropical Pacific basin wide surface westerly wind event with anomalies well in excess of 10m/s which helped to strengthen the warm ENSO. To me, this is a situation of tropics forcing extratropics (including from the MJO and ENSO in this case) and then extratropics forcing back (with properly phased wave trains) to maintain an “equilibrium weather-climate situation” through the interactions of multiple time scales.

A “repeat” of the above recently occurred about 5 days ago with another flare-up of date line tropical forcing (~every 20 days for a time-scale?) which led to intense baroclinic storm development from the central/southern Rockies to the eastern part of the USA. A difference is the MJO signal had re-emerged into the Eastern Hemisphere (and weakened). The models did struggle with the synoptic details of this storm (which was responsible for a blizzard across eastern Colorado and possibly more than 2 dozen tornadoes across Southwest Kansas).

Is the recent intensification of the Indian Ocean convection going to “disrupt this feedback loop?” Has this latest MJO caused our warm event to (finally) peak? Are we going to see 2 (or more) regions of tropical forcing with the Indian Ocean convection (eventually spreading east inconsideration of the SSTs?) becoming dominate at some point? Will there be another coherent MJO signal? These are just some of the issues that are unclear.

Evidence of circulation impacts from the variability of the date line tropical forcing can also be seen from plots of the earth-atmosphere AAM budget available from ESRL/PSD (using the re-analysis data and its 1968-97 climatology). Loosely, around 1 October global relative AAM tendency was positive with positive global mountain and frictional torques. That all reversed by about the middle of this month only to recently become positive (magnitudes ~10-20 Hadleys). Global relative AAM has lagged by roughly 10 days.

There has also been poleward propagation of zonal mean westerly wind anomalies into both the midlatitude and subtropical atmospheres of the Northern Hemispheres with anomalies ~5-10m/s at 200mb linked to the tropical forcing. Animations of both 150mb and 250mb daily mean vector wind anomalies show the presence of anomalous twin subtropical anticyclones across the Western Hemisphere coming back into the Indian Ocean while a separate pair persists near the date line. The former have been associated with the MJO signal while the latter is at least partly from ENSO. There is a well defined subtropical jet (STJ) extending from the date line pair (as also seen from full-disk satellite water vapor imagery) with additional enhancement from the anticyclones downstream. Anomalies with this STJ have been in excess of 25 m/s at 150mb at times.

Overall we have a weather-climate situation I would offer is best described by GSDM Stage 4 but with additional complexity due to the date line tropical forcing. I have been terming the latter as a signal due to the current warm phase of ENSO throughout this discussion. However, in reality I think there may be even slower time scales involved with this along with “other processes”, in addition to ENSO.

To summarize, I think we have 1) a warm event (plus a global warming signal whose cause is unclear?), 2) possibly an increasing role of the Indian Ocean SSTs, 3) the MJO signal which may become very weak, 4) 20-30 day tropical convective variability, 5) some evidence of mountain-frictional torque index cycle variations (not discussed – may be linked to (4)), fast RWDs, baroclinic wave packets and all sorts of other white noise, and 6) seasonal cycle issues.

The latter (6) may involve just how sensitive the response across the Asia-PNA sector will become to tropical convective forcing (or lack of) as the climatological strengthening of the East Asian Jet (EAJ) occurs. For instance, if we do get into a situation of 2 regions of tropical forcing (with suppression, say around the Philippines), the response may become GSDM Stage 1 with STJs through late December. Afterwards, as both the convection and EAJ shift south, enhanced convection across the central Pacific may become dominate and lead to GSDM Stage 3 by sometime in January. We will see.

In what follows, I am leaning toward my notion of consolidation of the tropical forcing during weeks 1-2 per above. Afterwards, I think it is unclear to offer anything statistically useful without additional tools. Confidence remains as low as it can ever get making week 1-3 predictions in this weather-climate situation. This is why detailed disciplined daily monitoring is critical.

Week 1 (28 October – 3 November 2006): GSDM Stage 4 with additional forcing from the central Pacific appears probable. The models are generally consistent with mid/upper tropospheric trough development across the east Pacific (~140W) with a downstream ridge along the west coast and subsequent eastern states trough by early next week. I see no reason to differ given the central Pacific twin subtropical anticyclones. At some point I would expect the westerly flow to increase across East Asia as trough development occurs there. This should allow the east Pacific trough to approach the west coast going into week 2.

This situation is generally dry for most of the country with warm conditions across the western states and cool for the east (not all the unusual for this time of year). The Pacific Northwest should have increasing opportunities for rainfall. There may also be opportunities for rainfall across the Deep South at times tied to the STJ.

Week 2 (4-10 November 2006): GSDM Stage 1 with an above average STJ may be most probable. At this point particularly the Pacific Northwest may receive substantial precipitation, which could spread slowly south. Depending on how far inland the trough gets, cooler and wetter weather may become more likely for the portions of the Rockies. The rest of the country may see above normal temperatures.

Week 3 (11-17November 2006): Unclear; however, an eastward progression of the situation discussed for week 2 would be reasonable if there is any truth to it.

Climatologically this is still the dry time of the year for Southwest Kansas. The recent storm/rain event was a pleasant “surprise (other than the tornadoes depending on your perspective)”. Week 1 looks generally dry with near-below normal temperatures (on average). Dryness may continue well into week 2 while temperatures may warm to well above average. Jet streaks along the STJ could give us at least a minor precipitation surprise by then. An active regime may return for this part of the world week 3 (for this time of year).

I will be on travel to ESRL/PSD next week so I do not know when there will be another posting on this Blog (perhaps a short one ~ middle of next week). We do have plans to write another weather-climate discussion for the ESRL/PSD MJO web page to hopefully post by the end of November. Please see the Appendix.

Appendix

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

From taking into consideration the interactions of 4 different subseasonal time scales, a sequence of maps 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 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.Our latest weather-climate discussion dated August 18th, 2006 (and updated September 9th), has been posted on the ESRL/PSD MJO web site at

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

Ed Berry

Update on What Goes Around Gets Messy -- written 10/21/06

This posting will be very brief. I hope to do a more complete effort late this upcoming week after I have completed covering overnight shifts (~10/26-27/06). Please see other postings for all web links.

The spatial distribution of global tropical SSTs are consistent with a mature warm ENSO. Strong westerly wind anomalies (~10m/s) and actual westerlies remain across the equatorial date line region. In fact, TAO buoy data suggest a downwelling oceanic Kelvin wave has developed east of the date line and is moving east along the equatorial cold tongue. We will see how robust this warm event gets (there is always uncertainty in many different aspects). At this point odds would favor above normal surface temperatures for especially the north central states during DJF and JFM (see CPC outlooks). However, please remember these are seasonal mean indications and this does not at all rule out possibilities of extreme cold episodes along with other forms of high impact severe winter weather for the northern or any portions of the USA.

The dynamical signal with the MJO is moving into the Eastern Hemisphere while SST boundary forced tropical convection slowly increases across the central Indian Ocean and west Pacific (per full disk satellite imagery). Three-day mean charts of OLRA indicate enhanced rainfall is present just south of the equator ~60E, 160E-160W including the SPCZ and from much of northern South America into the Atlantic ITCZ. Anomalous upper tropospheric twin tropical/subtropical anticyclones (with lower level westerly anomalies – baroclinic response) accompany these 3 regions, particularly for the MJO dynamical signal.

Re-analysis data plots from ESRL/PSD shows global relative AAM tendency has become strongly negative (as of 10/18) with a magnitude of ~ minus 25 Hadleys. Both the global mountain and frictional torques are contributing. Zonal mean easterly wind anomalies are replacing westerly anomalies throughout the tropical and subtropical atmospheres while existing westerly anomalies propagate into the midlatitudes of both hemispheres. In this type of situation a synoptician is going to see a tendency for troughs and ridges to become northeast-southwest oriented across the Northern Hemisphere along with features such as anticyclonically wave breaking (AWB) “upper level lows”. These tilts will contribute to AAM being fluxed poleward from the tropics into eventually the midlatitudes.

GSDM Stage 4 best describes the current weather-climate situation. The future evolution of the tropical convective forcing is unclear, including if there will be another MJO. My own thought is we may see some consolidation of the tropical forcing across the Eastern Hemisphere during the next 1-3 weeks, perhaps around 10N/90-120E to the north of the cool Indonesian SSTs. While this may be occurring, the date line region and even the SPCZ may continue experience tropical convective flare-ups (there are still the ~20-30 day tropical convective variability and convectively coupled Kelvin waves going on). Locations such as the South Indian Ocean-Bay of Bengal and west central and South Pacific may be vulnerable to tropical cyclone development (and we need to watch the Caribbean and even the North Atlantic for especially hybrids). During weeks 2-3 GSDM Stage 1 with subtropical jets may be most probable particularly for the Asia-PNA sector. This would suggest western North America to become increasingly at risk to strong synoptic-scale troughs while an active storm track develops across the Plains possibly going well into November. Most readers should be familiar what all this means in terms of weather particularly if a cold air source evolves during November.

Ed Berry

ENSO and Complexity Making a Comeback

Please see past postings for web site links. I am going to discontinue inserting most of them in an effort for brevity. I also need to do the same with these postings.

The spatial distribution of global tropical SST anomalies continues to resemble a mature warm event, with positive values across the western Indian Ocean and along the equator from ~140E-South America with cool readings around Indonesia particularly south of the equator. In fact, the SST horse shoe pattern of cool surrounding warm anomalies (would be reversed for a cold event) across the tropical Indo-Pacific is quite well defined. Anomalies are generally from 1-2C with magnitudes around 3C along the East Pacific cold tongue, extending to depths of ~200m around the date line. SSTs of 29C and warmer cover much of the equatorial date line region, the central Indian Ocean and both sides of Central America. Weak positive SST anomalies cover most of the tropical Atlantic with actual temperatures ~28-29C.

SST and SST anomaly tendencies during the past week or so have reinforced the spatial distribution discussed above. Magnitudes have been ~plus .5-1C, with the warming along the equatorial cold tongue the result of a basin-wide surface westerly wind event whose anomalies have exceeded 10m/s (more said below). At this point our warm event has become better defined during the past 1-2 weeks. I have expressed concern in past writings this event may have already peaked. Whether or not this is the case, is unclear to me, as is the future for this warm ENSO (there are seasonal cycle issues). Whatever the case, the SSTs linked to this ENSO evolution have already impacted synoptic variability across North America since at least June 2006, and are doing so as I type.

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

Please also see the following CPC link (and others therein) for further ENSO, etc., insights, and remember that official USA information on anything related to ENSO comes from CPC.

http://www.cpc.ncep.noaa.gov/products/predictions/90day/

Per coherent modes and velocity potential Hovmollers (and other monitoring tools), the dynamical signal with the MJO is in the Western Hemisphere ~0/60W having a phase speed of ~10-15m/s. The MJO signal typically propagates eastward much faster across the Western Hemisphere due to less air/sea coupling with cooler SSTs (loosely acting like a Kelvin wave enhancing upper tropospheric divergence). Full disk satellite imagery shows quite a bit of convective enhancement centered on northern South America with OLRAs ~minus 50-90W/m**2. The recent heavy rainfall across the USA Deep South had a contribution from this MJO signal as the result of a local enhancement of the subtropical jet (STJ) via complex interactions with the extratropics.

Well defined twin upper tropospheric subtropical anticyclones are present around 90-120W (including the Gulf of Mexico) with wind speed anomalies ~20-30m/s per animations of 150mb daily mean vector wind anomalies. Additionally, Rossby wave energy is dispersing into the extratropics of both hemispheres leading to, for example, a negative projection onto the North Atlantic Oscillation (NAO).

Full disk satellite imagery also shows tropical convection increasing across the west central Pacific centered ~0/150-160E as well as the equatorial Indian Ocean ~60E, while strong suppression remains across Indonesia with positive values of OLRA in excess of 70 W/m**2 ~0/100E. This spatial pattern of enhancement-suppression-enhancement across the Eastern Hemisphere would be expected from the SSTs, with the former termed by some folks as a positive phase of the Indian Ocean Dipole (IOD) and the latter due to ENSO. It is typical to see a warm western Indian Ocean during a mature warm ENSO, and I like to understand climate variability as dynamical processes involving forcing-response-feedbacks (and so on) globally interacting with regional behaviors, etc.

After reaching a positive maximum of ~20 Hadleys (reanalysis data climatology from 1968-1997) just before October 1st, the global tendency of relative AAM has dropped to ~minus 10 Hadleys as of October 14th. As expected with a MJO, this positive AAM tendency started along/just south of the equator ~ September 18th, and has coherently propagated poleward into both hemispheres, particularly across the Northern Hemisphere (currently around 40N). A time-latitude section of 200mb zonal mean zonal wind anomalies loosely shows this poleward propagation, with westerly anomalies currently ~5-10m/s centered at about 30N (one level as opposed to a vertical integral).

After roughly October 1st there was relative AAM flux divergence from about 45N (sink) leading to flux convergence near 30N (source; we are looking at divergence of the AAM transports), again consistent with the dynamical signal of the MJO moving into the Western Hemisphere. This redistribution of AAM helped to weaken the midlatitude flow while increasing the westerly flow across the subtropics (including the STJ). A forecaster looking at a polar stereographic projection map of 250mb total vector winds (for example) would have observed a split flow pattern along the North American West Coast at times during this period as a response.

The point is using monitoring tools such as AAM tendencies and transports allows some understanding of the recent increases of the zonal mean westerly flow throughout the subtropical and midlatitude atmospheres. Through tropical-extratropical interactions involving the midlatitude synoptic eddies (reader needs to think about this) not only have we seen the central and east Pacific basin wide surface westerly wind event (discussed above), there has also been a strengthening of the North Pacific jet over the last 1-2 weeks, the latter having seven-day mean anomalies of ~20m/s. For the USA the result has been recent PNA responses (from Rossby wave energy dispersions -- index sign depends on location of features; one weakness of it) and an enhanced STJ all contributing to recent cool outbreaks for the central states and heavy rain for the Deep South. Please see our recent weather-climate discussion dated August 18th as an example to interpret some of these behaviors (link below).

The enhanced surface westerlies across the north tropical Pacific Ocean basin for at least the past 1-2 weeks has brought the global frictional torque down to around minus 20 Hadleys, and the global mountain torque is also starting to decline (see ESRL/PSD plots for details). GSDM Stage 2 would best describe the weather-climate situation from roughly October 1-14 (at times tilting toward Stage 3), with a loose GSDM Stage 4 the last few days. Animations of 150mb and 250mb daily mean vector wind anomalies once again present a strong signal of anomalous twin tropical/subtropical anticyclones around 160E tied to the tropical convective flare-up in that region (with well defined twin cyclones ~90E tied to the suppression; this is a baroclinic process). A Rossby wave energy dispersion is in progress and will lead to another PNA. This has some similarities to what occurred around October 8th, except the MJO dynamical signal is now in the Western Hemisphere, as opposed to the west Pacific. In fact, upper tropospheric easterly wind anomalies of ~20-30m/s at 150mb have been appearing across the equatorial east Pacific during the last few days, having more consistency with Stage 4 as opposed to Stage 2. This all suggests a retrogression of existing circulation anomalies during the next few days or so across the northern extratropics particularly from Asia-North America (“bottom line”).

To summarize, I think we have 1) a warm event (with the understanding of Indian Ocean-Pacific SSTs) whose future evolution still remains unclear (but likely to persist into 2007), 2) at least a moderate MJO signal moving across the Western Hemisphere, 3) intensifying tropical convective forcing from the Indian Ocean, 4) a mountain-frictional torque index cycle, 5) baroclinic wave packets/fast Rossby wave energy dispersions interacting with the west central Pacific tropical forcing, and 6) seasonal cycle issues.

There are other matters I am unclear about such as any sub-monthly component involving the mountain torque and other faster modes of tropical convective variability. The future of the MJO even after week 1 is also unclear. I do think the dominant forcing from the tropics is coming from the west central Pacific, and it may not just be a warm ENSO signal. The SSTs are also cool across the tropical northwest Pacific (opposite of last year) and the evolution of this whole “SST situation” is anything but trivial to understand. It would be interesting to see how well coupled GCMs would simulate these SST events since the start of this year.

In any case, we must also remember the suppression from Indonesia also has circulation impacts, and I can easily see Indian Ocean tropical forcing disrupting events across the west Pacific. The statistical models (Wheeler phase space technique, for example) bring the dynamical signal well into the Eastern Hemisphere (~60-80E) by about day 10, and I think that is reasonable. My own thoughts is there may be 2 well defined regions of enhanced tropical convection during week 2, the Indian Ocean and west central Pacific, while the Western Hemisphere becomes suppressed. During week 3 there may be some consolidation of the 2 regions north of the cool SSTs across Indonesia. Confidence in any scientifically defensible statistically useful prediction particularly beyond week 1 is as low as it gets. This is the real world!

Week 1 (18-24 October 2006): I think a loose rendition of GSDM Stage 2 is most probable, but roughly 5-10 degrees farther west (for the USA) than about a week ago. This would mean a trough ~100W with a large amplitude ridge just off the USA west coast possibly into Alaska. Nearly all models are predicting some version of this response since the Rossby wave energy dispersion discussed above should be in the initial conditions. This means a much cooler than normal regime for a good part of the country especially the central and north central states. The warm locations may be the West Coast and Florida. One surge of cool air is occurring as I type, with another due by this weekend per operational NCEP GFS (and other models).

I have a bit of concern for this second surge of cool air. The jet streak that will contribute to it (interacting with “everything else”) may involve the remnants of Typhoon Soulik. The baroclinic development which ensures on the Plains by this weekend may begin with amplification of the trough a bit farther west into the central Rockies. That may suggest more robust cyclogenesis across the Mid/Upper Mississippi Valley. Even though moisture will be relatively limited, a “decent” snow event is not out of the realm of possibilities for locations such as Iowa into the Great Lakes (latter including lake effect). Other effects on the weather should be apparent.

The Tropical North Atlantic may remain suppressed for tropical cyclone activity. There is always the concern for hybrids this time of year and I could also see a period of upper tropospheric easterlies across the tropical Atlantic, latter perhaps allowing a window of opportunity for development. Please see http://www.nhc.noaa.gov/ for the latest tropical cyclone information. Active regions for tropical cyclones may include the west central Pacific and even the Bay of Bengal, particularly weeks 2-3.

Week 2 (25-31 October 2006): If the west Pacific is “calling the shots”, then similar to week 1 except for the usual synoptic variations of amplitude.

Week 3 (1-7 November 2006): I can envision possibilities (like anyone else), but let us just say “unclear” for now.

Climatologically this is the dry time of the year for Southwest Kansas. Other than one or two minor episodes of precipitation, week 1 looks generally cool and dry. There is a small possibility of a “surprise” this weekend. I would expect week 2 to remain generally dry with roughly seasonable temperatures (on average!). Even though not discussed for week 3, opportunities for precipitation may increase for this part of the world should “STJ activity” become more robust.

Since I continue to have to cover lots of shifts (including mids), I may not be able to update this Blog until late next week. We do have plans to write another weather-climate discussion for the ESRL/PSD MJO web page to hopefully post by the end of November. Please see the Appendix.

Appendix

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

From taking into consideration the interactions of 4 different subseasonal time scales, a sequence of maps 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 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.

Our latest weather-climate discussion dated August 18th, 2006 (and updated September 9th), along with all the other issuances, has been posted on the ESRL/PSD MJO web site at

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

Ed Berry

Weather-Climate Update

Please see past postings for web site links. I am going to discontinue inserting most of them in an effort for brevity. I also need to do the same with these postings, and this one will be short due to shift work obligations.

SSTs have changed little since my posting on October 6th. There is some evidence that the current warm phase of ENSO is peaking.

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

Please also see the following CPC link (and others therein) for further ENSO, etc., insights, and remember that official USA information on anything related to ENSO comes from CPC.

http://www.cpc.ncep.noaa.gov/products/predictions/90day/

The dynamical signal with the MJO is propagating through the Western Hemisphere, with a phase speed of 10-15m/s based on Hovmollers of velocity potential and OLRA. This is an increase from about 2 weeks ago, and is typical when the MJO signal moves into the Western Hemisphere. Full disk satellite imagery suggests the dynamical signal is centered around 0/80W. Surface westerly wind anomalies of 10-20m/s have propagated northward from the equatorial date line region and have contributed to anomalous westerly flow across much of the North Pacific at ~30N during the last few days. The latter was theresult of 2 tropical convective flare-ups and westerly wind events during the last 10-14 days, and has been associated with tropical cyclone activity across the West Pacific. In fact, there is a signal in the global AAM tendency of the tropical convective flare-ups associated with the MJO.

In the upper troposphere, 200mb zonal mean zonal wind anomalies of ~5m/s are presently centered ~20N, and there is evidence of meridional symmetry. Additionally, some linkage between the anomalous zonal mean westerly flows throughout the subtropical and midlatitude atmospheres has occurred during the last few days. Loosely, GSDM Stage 2 (tilted toward Stage 3) best describes the weather-climate situation during the past week. This has impacted the USA in the form of the currently strong positive phase of the Pacific-North American teleconnection (PNA). A major cold outbreak (for this time of year) into the North Central states is occurring as a response.

Strong suppression exists across much of the Eastern Hemisphere while convection remains perhaps coupled to the warm SSTs just west of date line, oriented north-south across the equator over the 29C and greater SSTs. The latter region has been weakening after the development of Tropical Cyclone Soulik. Most of the tropical convective enhancement is along the East Pacific ITCZ (where SSTs are also warm) into the South Atlantic Convergence Zone (SACZ) and spreading into the tropical North Atlantic ITCZ. This activity is associated with "wavy" upper tropospheric westerly wind anomalies that normally develop downstream of tropical forcing over the Eastern Hemisphere.

My thoughts are for the dynamical signal to propagate into the Eastern Hemisphere by the week 2-3 time frame, and reinvigorate the tropical convection across much of the Indian Ocean (where are SSTs are also quite warm with anomalies ~plus 0.5-1C over greater than 29C water). SST boundary forced tropical convection would also be expected to continue just west of the date line. A rendition of GSDM Stage 4-1 may be probable during weeks 2-3, loosely suggesting a retrogression of existing circulation anomalies with the continuation of subtropical jets. Many numerical ensemble prediction systems are capturing this scenario for much of the northern extratropics for week 2.

Ramifications would include the possibility of an anomalously deep trough across the western USA (with a subtropical jet), along with a strong southwest flow storm track across the Plains and central portions of the country. While synoptic details are unclear (ex., the magnitude of any baroclinic cyclogenesis), there exists the possibility of an early season major winter-like storm for the Central and Northern Rockies (there will be a cold air source). Meanwhile, severe local storms and widespread rainfall (some heavy) would be possible for locations from the Plains into the Upper Mississippi/Ohio Valleys and Great Lakes states. Other weather anomalies from this type of pattern should be well known by now.

I hope to post a more complete discussion roughly a week from today.

Ed Berry

Appendix

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

From taking into consideration the interactions of 4 different subseasonal time scales, a sequence of maps 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 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 and additional components.

Our latest weather-climate discussion dated August 18th, 2006 (and updated September 9th), has been posted on the ESRL/PSD MJO web site at

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

We hope to post another writing on the ESRL/PSD MJO web site within the next 4-6 weeks.