Sunday, November 25, 2007

Postponed again

It is unlikely I will write another complete discussion for this Blog until next weekend at the soonest. Briefly, the change to the USA cold regime I discussed roughly a week ago is generally on track. However, globally westerly wind flow throughout the atmosphere has increased dramatically over the last 7-10 days. Global relative AAM is currently near to slightly above average, up ~3AMUs. The eastward shift of tropical convective forcing to ~0/160E, strong positive surface torques and suspected eddy feedbacks have led to the rapid increase in westerly flow. Largest zonal mean contributions have been from the equatorial and midlatitude atmospheres of both hemispheres.

Phase 5 of the GWO best describes the global weather-climate situation. I think we are in the process of a having a large circuit of the GWO. A wind signal from the MJO is contributing. An important monitoring issue will be to see how far west the tropical convective forcing redevelops across the Eastern Hemisphere during the next few weeks. I speculate that the current extension of the East Asian jet will "break through" the eastern Pacific ridge ~week 2, followed by re-amplification of existing PNA circulation anomalies ~20-30 deg of longitude farther west weeks 3-4.

Appendix

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



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

We call the behavior of this plot the Global Wind Oscillation (GWO). While the intent of the legacy GSDM is to extend current thinking beyond the MJO, the GWO quantifies variations used to derive the original GSDM in a manner that is “user friendly” analogous the WH2004 “convention”. In addition, the GWO plot does not have the ENSO signal removed.

Links to CPC and PSD ENSO discussions:

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


These are probabilistic statements, and work is ongoing to quantify in future posts (for example, risk assessment composite maps, composite signal to noise ratio plots and shifts of probability). We hope that an opportunity will arise for us (soon) to have a dedicated web page effort to expedite more objectively, with rigor, thoroughness and verification. The WB (2007) paper on the GSDM has been published in the February issue of MWR. I will try to post a complete discussion next weekend.

Ed Berry

Sunday, November 18, 2007

El-Viejo Update

This posting will be short. One motivation for attempting to “get something out” is my concern for a change to a significant to perhaps severe winter regime focusing on the USA Rockies and Plains by week-3 (roughly the first week in December). Of course, there are always timing issues, and the above statement is made from my conservative perspective when it comes to making any kind of weather predictions.

The same weather-climate issues discussed on my 10 November, 2007, posting remain. The dominate tropical convective forcing has shifted east to ~0/140E during the past week. This was more of an eastward push than I expected a week ago; however, not surprising. Several tropical cyclones have been and still are occurring across the Indo-Pacific region. I am optimistic that the Bay of Bengal tropical cyclone season is “over with”. The low confidence amplification across the Asian-North American sector I also offered a week ago is in progress as I type. Numerical ensemble prediction schemes have been “playing catch-up” to this initial first regional scale response to La-Nina and tropical convective forcing.

Global relative AAM has risen slightly to ~minus 2 standard deviations below the R1 data climatology (14 November last update) with the recent development of equatorial zonal mean upper tropospheric westerly wind flow anomalies. The latter are most robust west of South America, having magnitudes ~20-30m/s. Anomalous twin upper tropospheric subtropical anticyclones have redeveloped ~120-140E, forced by the tropical convection. Rossby wave energy dispersions from these anticyclones will deepen a trough into the Rockies and Plains by the middle of this upcoming week, leading to what may be this cold season’s first winter storm for the Upper Mississippi Valley and Great Lakes regions.

The punch line is that the above mentioned tropical forcing may be the final step for mature coupling to La-Nina. Typically for the ENSO “cycle”, often a MJO or other tropical convective forcing leads to mature coupling during January of the annual cycle. We are concerned this process is starting sooner. Zonal mean subtropical easterly wind flow anomalies remain very intense poleward of the equatorial westerlies already discussed across both hemispheres. At this time, an evolution toward phase 5 of the Global Wind Oscillation (GWO; legacy GSDM Stage 2) appears to be in progress. Updated through 14 November global relative AAM tendency was ~plus 20 Hadleys with the calculated tendency ~plus 30 Hadleys.

Even though statistical tools such as the WH2004 RMMs already indicate and predict a robust MJO during the next couple of weeks, I disagree with that notion. One important point to remember is that these types of techniques do remove the ENSO signal, and that is a problem given the current situation. I do think it is probable for a fast dynamical signal to propagate through the Western Hemisphere over the next couple of weeks. However, as already indicated by satellite imagery, the tropical convective forcing ~140E is starting to “break apart”. One portion should retreat back to the west-northwest while the other enhances a westward shifted South Pacific Converge Zone (SPCZ). Additionally, tropical convection is re-firing across the warm Indian Ocean just south of the equator. Bottom line is tropical forcing should re-intensify back to west ~80-120E during the next few weeks, forcing the GWO back to ~phase 3 (legacy GSDM Stage 1).

For the PNA sector, I think there is a real possibility for a corresponding westward shift of circulation anomalies by early December, perhaps leading to a blocking ridge into Alaska ~140-150W and extratropical cold lows even impacting the USA west coast before coming inland. Cold Arctic air has been recently building up across portions of Siberia into northern Canada. If there is any correctness to these notions, this Arctic air may dump into the USA including locations west of the Continental Divide starting week-2. Weeks 3-4 may see the classic moist southwest flow storm track across the Plains, with intense cold focusing on the Rockies and Northern Plains while the Deep South has above normal temperatures. Areas such as the Desert Southwest and the southwest High Plains may also have decent precipitation in spite of the La-Nina signal. Other weather impacts may include snowfall for Pacific Northwest cities such as Seattle and severe local storms and heavy rainfall from the lower Mississippi Valley into the Ohio Valley.

Finally, any seasonal mean DJF 2007-08 anomalous cold air surface temperature signal which could in reality occur for portions of the USA may be dominated by December. It will be interesting to observe subseasonal activity starting January as tropical convective forcing shifts toward the very warm west central and southwest Pacific Ocean. Will we start to see our "Nemesis"? Is El-Nino in the cards for 2008-09, perhaps even a strong one???

Please see the latest statements from the NOAA/NWS/Tropical Prediction Center and other international centers for tropical cyclone statements. Areas including the Northwest Pacific Ocean around the Philippines, as well as from the South Indian into the Southwest Pacific Oceans including the "paradise islands" may have concerns for tropical cyclones through week-2. Finally, episodes of strong/severe synoptic baroclinic cyclonic systems hammering at least portions of Scandinavia, Europe into the Mediterranean countries/northwest Africa remain probable through week-2.

Appendix

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



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

We call the behavior of this plot the Global Wind Oscillation (GWO). While the intent of the legacy GSDM is to extend current thinking beyond the MJO, the GWO quantifies variations used to derive the original GSDM in a manner that is “user friendly” analogous the WH2004 “convention”. In addition, the GWO plot does not have the ENSO signal removed.

Links to CPC and PSD ENSO discussions:

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


These are probabilistic statements, and work is ongoing to quantify in future posts (for example, risk assessment composite maps, composite signal to noise ratio plots and shifts of probability). We hope that an opportunity will arise for us (soon) to have a dedicated web page effort to expedite more objectively, with rigor, thoroughness and verification. The WB (2007) paper on the GSDM has been published in the February issue of MWR. I will try to post another discussion around late next weekend or early week-2.

Ed Berry

Saturday, November 10, 2007

El-Viejo Keeps Rocking

There has not been a lot of change to the tropical global SST pattern during the past week. Equatorial Pacific Ocean cold anomalies remain from the west coast of South America to ~160E, with the greatest magnitudes ~minus 3C at about 120W. There is some possibility this cold event may be nearing maturity since the coldest subsurface anomalies have apparently surfaced and magnitudes only around minus 1-2C exist just below the surface east of 150W. Plus 0.5-1C subsurface anomalies (as deep as 150m) remain along the equator from 160W to at least 140E. It is probable for the western tropical Pacific Ocean to remain relatively convectively suppressed thorough at least December (Nemesis is still around), meaning SST anomalies across the warm pool region may increase.

The west central Pacific Ocean still has totals in excess of 30C currently just south of the equator at 140E slowly shifting into the Southern Hemisphere with the annual cycle, linking to a well pronounced positive SST horseshoe into the global midlatitudes. In fact, in the regions of 30-40N and S latitudes, Pacific Ocean SST anomalies are well in excess of plus 3C (totals 22C and colder) as a response to persistent intense subtropical anticyclones. This is a situation of the atmosphere forcing the ocean, unlike the ocean forcing the atmosphere as typically occurs across the deep tropics. Many will argue feedbacks occur from extratropical SSTAs such as these; however, they are only secondary. For instance, should the current intense North Pacific Ocean jet persist, significant SST cooling will occur across that region.

There is once again the warm-cool-warm Indian Ocean to west central Pacific SSTA distribution, with totals in excess of 28C across the equatorial Indian Ocean. I am not going to “go there” in regard to Indian Ocean Dipole (IOD) issues. The Atlantic basin is still warmer than climatology, with a bit of an increase during the past week. Should we start talking about the 2008 North Atlantic tropical cyclone season? Who knows, there may be one or two “Gabrielle-like” systems across the South Atlantic around March 2008.

Repeating from a week ago, the following link is to the WMO news page where a nice discussion about the evolution of this cold event is posted. I recommend reading it, paying attention to the “unusual” characteristics noted.

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

Full disk satellite imagery and other diagnostic monitoring tools present a nice signal of consolidation of tropical convective forcing ~0/90-100E during the last week. The eastward shift into the west central Pacific Ocean discussed last posting has lost coherence. What is left of it is centered ~0/140-150E, while drifting west. I think a combination of these two regions of tropical convective rainfall centered ~0/120E is probable during the next week (or less). Generally diurnal rainfall is present around central/South Africa with some suppression over tropical South America.

I think we are starting to observe the “composite La-Nina” response of tropical convective forcing. However, I do expect this Eastern Hemisphere region of tropical convection to shift east into portions of the west central and even South Pacific (along the SPCZ) especially early 2008, within envelops of other subseasonal variations. There is little, if any, signal of a MJO at this time. Attention needs to be paid if the above convection starts to move east coherently during the next few weeks.

The global circulation has essentially coupled to La-Nina in terns of SST forcing, tropical convective and circulation responses. Animations of daily mean upper tropospheric vector wind anomalies give a decent signal of twin tropical/subtropical anticylones centered ~110E with twin cyclones near the International Date Line. Anomalous zonal mean easterly wind flow anomalies (~5-10m/s at 200mb) persist across the subtropical atmospheres while weak equatorial westerly wind anomalies have become better defined over the Western Hemisphere. In fact, the latter are coming around into portions of Africa (implications are a monitoring issue). Within this coupled base state (GSDM Stage 1), a fairly well pronounced transient evolution partly linked to global topography has contributed to a strong (daily mean anomalies ~50m/s at 250mb) extended North Pacific jet about the slam the USA Pacific Northwest (more said below).

Global relative AAM remains extremely low, ~2.5-3 standard deviations (precisely AMUs) below the R1 data climatology through 7 November. This situation has been observed since about mid August 2007. While the equatorial Pacific SST pattern suggests the current La-Nina is best described as “moderate”, the global circulation is strongly La-Nina like (which could be viewed as seasonal-time scale extreme weather event). In fact, a defensible argument may be made that the tropical SSTs have been catching up to the atmosphere particularly since August. Other terms of the AAM budget also support the notion of a strong La-Nina circulation, including the inter-hemispheric symmetry of poleward AAM transports across the subtropics, and the mass term. The relatively persistent global positive frictional torque of roughly 10 Hadleys is coming from enhanced Northern Hemisphere trades trying to add angular momentum to the atmosphere from the earth. Typical of a cold event, the atmosphere continues to rotate slower than the earth.

The global weather-climate situation is solidly in GSDM Stage 1 as indicated by the Global Wind Oscillation (GWO) updated through 29 October. The GWO continues to orbit around La-Nina. While we can attribute the larger GWO orbits to non-oscillatory slow processes such as friction-mountain torque index cycles, the faster smaller circuits remain a topic of our research. The recent positive AAM tendency of ~20 Hadleys is coming from the tropics and lower midlatitudes. In addition to the current positive global mountain torque of ~15 Hadleys with East Asia leading, I think there has also been a contribution to the positive AAM tendency from the weak eastward shift of tropical forcing discussed a week ago. The strong North Pacific jet is a response from these combined tropical and midlatitude dynamics (bottom line). In any case, when updated, I think there will be another one of those “smaller orbits” of the GWO.

Instead of stating in the Appendix, we are continuing to rework the GSDM and use terminology similar to that of the WH2004 8-section phase space plots of the MJO. In other words, we will be getting way from terms such as “stages” and use phraseology such as “phases” instead. Stages may be used in reference to what will be referred to a the “legacy WB(2007) GSDM”. Hence GSDM Stage 1 will be “GWO phase 3”,GSDM Stage 3 will be referred to as “GWO phase 7”, etc. I know this seems very confusing; however, stay tuned, it will become much easier to understand. We are making these modifications partly in response to users who do not like the word “stages”.

Worth restating, I think the USA seasonal outlooks recently prepared by the Climate Prediction Center (CPC) are the “correct forecast” given La-Nina, keeping in mind to remain diligent for important subseasonal events. The subseasonal evolutions during November-December-January 2006-07 putting an unexpected demise to El-Nino serves as an excellent example. I also want to make clear that blanket statements about the roles of the North Atlantic Oscillation and/or Arctic Oscillation (NAO/AO) for a cold seasonal mean USA outlook are not scientifically defensible. From a subseasonal viewpoint the latter are responses to at times very complex dynamical forcing onto the global circulation and not that predictable especially beyond a few weeks.

Continuing thoughts from the previous posting, the extended North Pacific Ocean jet is likely to collapse during the next 1-2 weeks. Simplistically, it is not unusual to observe jets outrunning Eastern Hemisphere tropical convective forcing, especially boreal autumn. With the exception of episodes of high winds/heavy rainfall across the Pacific Northwest and perhaps portions of Alaska at times, a generally mild and tranquil weather pattern can be expected roughly week-1 for the USA. There will be some trough amplification east of the Mississippi River meaning opportunities for some precipitation and cooler air.

Perhaps most importantly, given the La-Nina coupling and upcoming probable collapse of the North Pacific Ocean jet, I think the possibility of significant amplification across the Pacific North American sector exists roughly days 10-20. Probabilistically, this would lead to blocking around Alaska and a western USA trough. I am making this statement with extremely low confidence, especially since my predictive insights have ____ recently. In fact, I am more confident about the amplification occurring then the synoptic pattern. For example, if the trough ends up across the east Pacific Ocean, while the USA west coast gets possibly hammered with cold systems the rest of the country may stay “boring” (yes, this scenario may also be good for ski resorts west of the Continental Divide). In any event, we need to monitor. If there is actually any truth to this possibility, people planning travel around Thanksgiving may have to deal with possibly intense winter weather should a southwest flow storm track develop across the Plains with an Arctic cold air source. Hopefully, the numerical models will start to support this synoptic evolution (not trying to “monger” winter).

I do think it is highly probable there will be several occurrences of the “classic” legacy GSDM Stage 1 (GWO phase 3) this cold season. Even with that circulation response, cyclonic baroclinic developments across the southwest High Plains may be too progressive for decent precipitation for locations such as the Desert Southwest into western Texas and eastern Colorado/western Kansas unless strong anticyclonic wave breaking of the lows can occur, say, around "4-corners".

Please see the latest statements from the NOAA/NWS/Tropical Prediction Center for tropical cyclone statements. Locations including the Bay of Bengal and the Northwest Pacific Ocean around the Philippines may have concerns for tropical cyclones week-1 and perhaps through week-2. I think flooding rainfall remains a concern for portions of Central America week-1. Finally, episodes of strong/severe synoptic baroclinic cyclonic systems hammering at least portions of Scandinavia, Europe into the Mediterranean countries are probable through week-2.

Appendix

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

http://www.cdc.noaa.gov/map/images/gcm/gsdm_95d.jpg

http://www.cdc.noaa.gov/map/images/gcm/gsdm_40d.jpg

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

We call the behavior of this plot the Global Wind Oscillation (GWO). While the intent of the GSDM is to extend current thinking beyond the MJO, the purpose of the GWO is to illustrate the non-oscillatory stochastically forced component of the GSDM.

Links to CPC and PSD ENSO discussions:

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

http://www.cdc.noaa.gov/people/klaus.wolter/MEI/

These are probabilistic statements, and work is ongoing to quantify in future posts (for example, risk assessment maps, signal to noise ratio plots and shifts of probability). We hope that an opportunity will arise for us to have a dedicated web page effort to expedite more objectively, with rigor, thoroughness and verification. The WB (2007) paper on the GSDM has been published in the February issue of MWR. I will try to post another discussion late next weekend or early the following week after travel.

Ed Berry

Saturday, November 03, 2007

The Devil (El-Viejo?) Reigns Supreme

Basin wide (within 5 deg of the equator) moderate La-Nina SST anomalies have intensified slightly during the past week with magnitudes ~minus 1-3C with the coldest along the equator at ~125W per recent 5-day averaged TAO buoy data. These kind of negative SST anomalies along the equatorial Pacific Ocean cold tongue are quite impressive in the presence of the seasonal cooling cycle. The cold anomalies extend down to roughly 200m deep west of South America and as far west at the surface to at least 160E. Strengthening of the near equatorial trades has assisted with the cooling SSTs around and west of the date line.

The west central Pacific Ocean still has totals in excess of 30C along the equator at 140E slowly shifting south with the annual cycle, linking to a well pronounced positive SST horseshoe into the global midlatitudes. Interestingly, weak cool anomalies have recently appeared across the North Indian Ocean, while the Atlantic basin is still warmer than climatology.

The following link is to the WMO news page where a nice discussion about the evolution of this cold event is posted. I recommend reading it, paying attention to the “unusual” characteristics noted.

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

Most dynamical and statistical forecast tools from global weather centers suggest this La-Nina to persist into at least early 2008. That notion is probable based on current subseasonal events (discussed below). However, the weak subsurface warming ~150-160W with anomalies ~plus 1C/150m, discussed last week, remains. Sparing lengthy details, I am unclear how this whole ENSO situation will behave during 2008. I would expect anomalous warmth to “build up” particularly west of the date line as boreal winter and austral summer take their course.

Monitoring satellite imagery and other diagnostic tools during the last few weeks tells me there has been a somewhat unexpected eastward shift of the Eastern Hemisphere tropical convective forcing from the Indian Ocean into Indonesia. Some projection onto a MJO was present, and this may have been, in fact, the truncated event I was expecting per past postings. However, I think the eastward movement has ceased, with consolidation and strengthening of the tropical forcing centered ~0/120-140E currently in progress. Other regions of enhanced tropical rainfall are also present across portions of west central-southeast South America/Brasil and Africa. There is also a weak flare-up across the west central Pacific responding to anticyclonically wave breaking cyclones from both hemispheres.

The gist is the global circulation is again coupling to La-Nina. I can see this even from plots such as Hovmoller representations of 250mb meridional wind anomalies in bands such as 10-40N. Global relative AAM is extremely low ~3 standard deviations below the R1 data climatology through 1 November. Since at least late September there have 2 “pulses” of poleward propagation of anomalous zonal mean easterly winds into the global subtropical atmospheres. Most recently zonal mean AAM anomalies ~minus 2 AMUs have appeared just south of 30N. This translates to zonal mean easterly wind flow anomalies as large as 10m/s at 200mb.

Staying on the topic of the AAM budget, a decent poleward transport signal has oscillated ~35N (weaker Southern Hemisphere signal) during the last week or so. This is why any astute synoptician would have been observing a lot of northeast-southwest (northwest-southeast) tilted eddies across the Northern Hemisphere (Southern Hemisphere) recently. The global frictional torque has increased to ~plus 10 Hadleys with a large source coming from the northern subtropics due to the intensifying trades. The global mountain torque has become slightly negative with a decent signal coming from the Andes Mountains.

In any case, I can very easily see how recent the AAM signals both globally and in the zonal mean are lining up nicely with the La-Nina coupling (SSTAs -> tropical convection-> circulation response, then subsequent interactions). The mass term in the AAM budget shows strong positive zonal mean anomalies (~.5 AMU) across the northern midlatitudes with the opposite over the tropics. This all translates to anomalously intense midlatitude ridges across the Northern Hemisphere. Another way to pitch this is that the atmosphere is currently rotating slower than the earth (increasing the length of the day by ~.005 seconds!).

The global weather-climate situation is solidly in GSDM Stage 1 as indicated by the Global Wind Oscillation (GWO) updated through 29 October. The GWO continues to orbit around La-Nina. While we can attribute the larger GWO orbits to non-oscillatory slow processes such as friction-mountain torque index cycles, the faster smaller circuits remain a topic of our research.

Animations of upper tropospheric daily mean vector wind anomalies give a nice signal of twin tropical/subtropical anticylones centered ~120E with twin cyclones just east of the date line. Anomaly magnitudes at 150mb are roughly 20-30m/s, including the equatorial westerlies across the Pacific west of South America. This is the typical baroclinic response to tropical convective forcing as part of the re-coupling to La-Nina.

The recent eastward shift of the Eastern Hemisphere tropical forcing is leading to an extension of the East Asian Jet as I type. This is an extratropical feedback response to zonally oriented Rossby wave energy dispersions interacting with the convection. Whether or not there will be a positive East Asian and global mountain torque with this event is unclear to me. However, not typical of GSDM Stage 1 and La-Nina is the upcoming development of an anomalous cyclonic circulation gyre across the central North Pacific Ocean per models (which I agree). This reminds a little of what we observed during November-December 2005 having a “Stage 3 circulation with Stage 1 forcing”. The Tropical Northwest Pacific Ocean (TNWP) was quite convectively active then. I speculate that since this La-Nina is stronger (and basin wide) than the 2005-06 event, and the TNWP SSTs do not appear as warm, we will not see our current North Pacific jet extension be as persistent and intense.

I think the USA seasonal outlooks recently prepared by the Climate Prediction Center (CPC) are the “correct forecast” given La-Nina, keeping in mind to remain diligent for important subseasonal events. The subseasonal evolutions during November-December-January 2006-07 putting an unexpected demise to El-Nino serves as an excellent example. I also want to make clear that blanket statements about the roles of the North Atlantic Oscillation and/or Arctic Oscillation (NAO/AO) for a cold seasonal mean USA outlook are not scientifically defensible. From a subseasonal viewpoint the latter are responses to at times very complex dynamical forcing onto the global circulation and not that predictable especially beyond a few weeks. Of course, once established, the decay time scales of the NAO/AO can provide some predictive information. Enough said!

As I stated a week ago, for especially the PNA sector, predictability has been VERY LOW for both myself (frustratingly) and the numerical models during the last couple weeks. In fact, week-two anomaly correlation coefficients (ACC) for both North America and the Northern Hemisphere for the NCEP ensemble mean have at times been near or below zero, per their web site. I think both the recent positive global mountain torque event discussed last week and the eastward shift of the tropical forcing discussed above have contributed to poor model performance. Yes, boreal autumn is also a tough time of the year for the numerical models, in general.

So what useful predictive insights can I offer today? I do think my “classic” GSDM Stage 1 response will occur “sometime”, favoring a western USA trough and southwest flow storm track across the Plains. However, that is not likely through at least well into week-two given the feedback issues discussed above, along with the seasonal cycle. The North Pacific Jet is very likely to blow across the northern part of the country by that time, in the presence of a low amplitude western states ridge and eastern USA trough. As the coupling strengthens, I can see a scenario of a brief GSDM Stage 3-Stage 4 evolution which may lead to a slower moving trough/closed low(s) across the southwest states perhaps later week 2-week 3. Until then, expect generally “boring” weather for the lower 48 states, except for those who enjoy dry weather and high fire dangers in places. As I have stated before, the latter is typical of autumn. Important exceptions are portions of Alaska and the Pacific Northwest where periods of very heavy rainfall and high winds are probable, and possibly the Great Lakes states for lake-effect snowfall and general "clipper systems".

Again, I emphasize the need for daily monitoring. To me, it is highly probable there will be several occurrences of the “classic” GSDM Stage 1 this cold season. Since timing is unclear, only monitoring may catch the evolution, and that may be before the models get it. Even with that circulation evolution, cyclonic baroclinic developments across the southwest High Plains may be too progressive for decent precipitation for that region unless strong anticyclonic wave breaking of the lows can occur over the Desert Southwest. During this upcoming cold season, given an Arctic cold air source, episodes of severe winter weather including substantial snowfall and blizzards may occur from the Northern Plains into the Upper Mississippi Valley while the Ohio Valley region has heavy rainfall and possibly severe thunderstorms.

Please see the latest statements from the NOAA/NWS/Tropical Prediction Center for tropical cyclone statements. Locations including the Bay of Bengal and the Northwest Pacific Ocean around the Philippines may have concerns for tropical cyclones through week 2. Heavy tropical rainfall may be probable for portions of South America and Africa also through week 2. I will let “Gabrielle” rest her soul.

Appendix

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

http://www.cdc.noaa.gov/map/images/gcm/gsdm_95d.jpg

http://www.cdc.noaa.gov/map/images/gcm/gsdm_40d.jpg

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

We call the behavior of this plot the Global Wind Oscillation (GWO). While the intent of the GSDM is to extend current thinking beyond the MJO, the purpose of the GWO is to illustrate the non-oscillatory stochastically forced component of the GSDM.

Links to CPC and PSD ENSO discussions:

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

http://www.cdc.noaa.gov/people/klaus.wolter/MEI/

These are probabilistic statements, and work is ongoing to quantify in future posts (for example, risk assessment maps, signal to noise ratio plots and shifts of probability). We hope that an opportunity will arise for us to have a dedicated web page effort to expedite more objectively, with rigor, thoroughness and verification. The WB (2007) paper on the GSDM has been published in the February issue of MWR. I will try to post another discussion around next weekend after travel, and before another trip the following week. I did fail to keep this discussion short!

Ed Berry