The GWO Giveth then Taketh Away?

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

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

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

Please see links below for global SST details. SSTs have been slowly warming across the convectively suppressed southwest into the central equatorial Indian Ocean. Anomalies are roughly plus 1-2C with totals approaching 30C. However, the South Indian Ocean remains anomalously cool on both sides of Australia into portions of central Indonesia. The former are the warmest I have observed “in a while”, and may signal the onset of enhancement of tropical convective forcing during the next few weeks (more said below). Finally, the Nino SSTs remain a bit cooler than normal and weak-moderate subsurface anomalies (~1-3C; see TAO buoy data) still suggest a steeper than normal equatorial thermocline.

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

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

http://www.pmel.noaa.gov/tao/jsdisplay/

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

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/index.primjo.html (link 19)

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

Sounding like the proverbial broken record during this 2008-09 La-Nina from Hell, the weather-climate situation is an extremely complicated mess, with lots of “tugs and pulls”. However, only from rigorous daily monitoring including evaluation of our “GWO-based diagnostic tools”, I do feel fairly comfortable with my interpretation. In the following, I again want to broad-brush, particularly since many readers are getting used to studying the budget terms of the on-line AAM plots, as well as the WB (2009) measure of the GWO.

Since October 2008, there have been “regular” ~25-30 day variations of the GWO, with each orbit spiraling toward the La-Nina attractor in phase space. This is a significant difference from the 2007-08 La-Nina, when slower subseasonal activity including MJOs occurred. Perhaps similar to the bear financial markets, the depths of El-Viejo were reached during late January and mid-late February. The latter were roughly 2-3 standard deviations below the R1 data climatology (the major SSW contributed; see past discussions), comparable to the strong “season of the witch” 2007-08 cold event. One direct response was for drought to intensify across many portions USA including the central and southern High Plains, while locations across the northern portion of country received significant to excessive precipitation.

Starting late February, dynamical processes explained by the GWO including meridional eddy momentum transports and the surface torques have worked hard to increase global westerly wind flow. Much of that contribution has been in the equatorial and Northern Hemisphere subtropical atmosphere, where upper tropospheric zonal mean westerly wind flow anomalies were ~5 m/s. Zonally oriented fast Rossby wave energy dispersions (RWDs)/subtropical baroclinic wave trains (SWT) involved with the GWO literally forced Indonesian convection into the anomalously warm southwest Pacific Ocean (SWP) by the middle of this month. I did not expect the latter (Rottweiler is very angry with me!). In any case, that was good news for many dry portions of the country.

The SWP forcing also did its part to add additional westerly wind flow to the global and various zonal mean bands of the atmosphere (including substantially decreasing intense subtropical zonal mean easterly wind flows). In fact, there was even a weak surface westerly wind event mostly south of equator having anomalies ~10m/s. Should this same type of behavior occur in May (for instance) across the west central Pacific Ocean on the equator, maybe this will be the start of an “exorcism”. Right now, in terms of the possibility of a warm event, I am not optimistic about that option. Through 24 March global relative AAM is only slightly below the R1 data climatology. Similar to what some may ask about the current bear market rally, is this AAM rally about to end?

Eastern Hemisphere tropical convective forcing has become incoherent. A “GWO-driven” MJO signal is moving through the Western Hemisphere. Just like that observed December 2008, this “MJO” evolved in the region of Indonesia, inconsistent with past documented work. That is why the WH (2004) measure of the MJO indicates ~1.5 sigma projection on octant 8 of phase space, updated through 26 March (ENSO removed). I do expect this signal to return to the Eastern Hemisphere during the next couple of weeks, and I think it is plausible to see some enhancement initially over the anomalously warm waters of the Indian Ocean (areas cited above).

Zonal mean subtropical easterly wind flow anomalies are starting to increase, and global relative AAM tendency has already become negative. As convection gets reestablished across the Indonesian region ~weeks 2-4, global relative AAM may decrease to at least 1 sigma below normal suggesting a re-loading of La-Nina (subseasonal perspective). However, seasonal cycle issues may also have an impact, and I do think we have seen the AAM bottom for this boreal cold season. Repeating from my last posting, we need to carefully monitor Southern Hemisphere zonal mean zonal wind anomalies this upcoming austral winter for ENSO insights.

The GWO is probable to do at least one circuit shifted toward octants 8-1-2 during the next 1-3 weeks. The corresponding GWO snr 250mb psi composite anomaly plots may best represent the global circulation the next few weeks. At some point GWO snr phase 3 (La-Nina base state) may return, meaning a positive phase of a Branstator (2002) circumglobal teleconnection favoring anomalous midlatitude ridges. The latter would not be good news to dampening many of the drought areas. Phases 4-5 of the MJO snr 250mb psi composite anomaly plots should loosely depict tropical circulation anomalies for the next few weeks. Obviously, phase 8 currently does not, which “tells you something” about calling the Western Hemisphere tropical convective dynamical signal (per velocity potential plots) a “MJO”.

More troughs are probable to impact the western and central USA during the next couple of weeks. While there will be a tendency for them to be progressive, I would not be surprised to see at least one more synoptic event similar (not the same weather) to the system currently pounding much of southwest Kansas with a blizzard as I write. At some point (perhaps late week 2/week-3) troughs may again dig off the west coast before shifting inland (trough-ridge-trough pattern for a period). Weather ramifications are understood, including internationally.

Appendix

All presentations from the 24 February 2009 GWO workshop are available via anonymous ftp. If you have not received information on how to retrieve these, let me know. There was excellent attendance at this day-long event, and feedback was strongly positive. We appreciate all the support!

Links to CPC and PSD ENSO discussions, and a new experimental forecast technique involving a coupled LIM (3rd link below):

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

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

http://www.cdc.noaa.gov/forecasts/clim/

The following are links to information about the stratosphere and other nice monitoring tools:

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

http://code916.gsfc.nasa.gov/Data_services/met/ann_data.html (new stratosphere link!)

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

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

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

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

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

The WB (2007) paper on the GSDM has been published in the February issue of MWR. The first of a two-part paper, where WB formally introduce the GWO (WB (2009)), is (still) awaiting publication in MWR. An early on-line release can be downloaded from the following link:

http://ams.allenpress.com/archive/1520-0493/preprint/2008/pdf/10.1175_2008MWR2686.1.pdf

In addition to the subseasonal snr composite anomaly plots, we would like near real-time discussions with “weather maps” to become a routine part of the ESRL/PSD GSDM web site sometime soon. Part-2 of our GWO paper will discuss the latter. We want to emphasize notions such as global-zonal mean-regional scale linkages as well as forcing-response-feedback (with subsequent interactions) relationships. An important purpose is to provide a dynamical weather-climate linkage framework to evaluate the numerical models in a sophisticated manner as part of a subseasonal (and any time scale) forecast process, in addition to a climate service for all users. Relying on the numerical models alone is a cookbook, extremely unscientific, and makes the Rottweiler VERY angry! I am planning on posting a discussion next weekend, 3-5 April.

Ed Berry

Update from the Midnight Rottweiler Rider

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

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

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

Please see links below for global SST details. This posting will be extremely short and hopefully coherent. A significant motivation to put “something out” is the extremely interesting on-going behaviors of the weather-climate dynamical system.

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

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

http://www.pmel.noaa.gov/tao/jsdisplay/

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

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/index.primjo.html (link 19)

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

Perhaps the “miracle” I was asking for per my last posting (14 March) is evolving. Multiple regions of enhanced tropical convective forcing are occurring across the globe. These include the quasi-stationary La-Nina signal ~0/100E, a “mixed GWO/MJO component” ~10S/155E, portions of northern Southern America and South Africa. For our purposes, the most important region is across the southwest Pacific Ocean (SWP; the 10S/155E signal), representing an enhancement of the SPCZ across very warm SSTs.

A well defined subtropical wave train (~25N) progressing through Asia is interacting with the SWP forcing. Divergent outflow from this strongly enhanced rainfall has locally strengthened the subtropical jet ~25N/180. Global relative AAM calculated tendency is solidly positive ~30 Hadleys, with contributions coming largely from the subtropical atmospheres of both hemispheres. There is evidence that zonal mean equatorward AAM transport is occurring ~30N, and synoptic behaviors such as northwest-southeast tilted eddies progressing off of East Asia support that. The bottom line is we do have a respectable perturbation on La-Nina, working to increase global westerly wind flow.

A probable regional-scale response will not only be the continued strengthening of the STJ impacting the southern USA, but possibly an eventual extension of the EAJ collapsing to more western states troughs ~weeks 2-3. These troughs may extend farther south helping to dampen areas experiencing drought. A superposition of phases 7-8-1-2 (models will struggle) of the snr 250mb psi MJO and GWO composite anomaly plots may best depict this situation.

Whether or not this subseasonal event is the start of a slow transition involving ENSO is unclear. Re-iterating, numerous GWO considerations tell us the La-Nina circulation anomalies will stick around. An important monitoring issue will be to see how intense zonal mean easterly wind flow anomalies become across the Southern Hemisphere subtropics during austral winter. Weather ramifications are understood, including internationally.

Appendix

All presentations from the 24 February 2009 GWO workshop are available via anonymous ftp. If you have not received information on how to retrieve these, let me know. There was excellent attendance at this day-long event, and feedback was strongly positive. We appreciate all the support!

Links to CPC and PSD ENSO discussions, and a new experimental forecast technique involving a coupled LIM (3^rd link below):

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

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

http://www.cdc.noaa.gov/forecasts/clim/

The following are links to information about the stratosphere and other nice monitoring tools:

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

http://code916.gsfc.nasa.gov/Data_services/met/ann_data.html (new stratosphere link!)

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

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

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

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

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

The WB (2007) paper on the GSDM has been published in the February issue of MWR. The first of a two-part paper, where WB formally introduce the GWO (WB (2009)), is (still) awaiting publication in MWR. A pdf of an in press version can be downloaded from the following link:

http://www.cdc.noaa.gov/map/clim/wb08_revised_final.pdf

In addition to the subseasonal snr composite anomaly plots, we would like near real-time discussions with “weather maps” to become a routine part of the ESRL/PSD GSDM web site sometime soon. Part-2 of our GWO paper will discuss the latter. We want to emphasize notions such as global-zonal mean-regional scale linkages as well as forcing-response-feedback (with subsequent interactions) relationships. An important purpose is to provide a dynamical weather-climate linkage framework to evaluate the numerical models in a sophisticated manner as part of a subseasonal (and any time scale) forecast process, in addition to a climate service for all users. Relying on the numerical models alone is a cookbook, extremely unscientific, and makes the Rottweiler VERY angry!

I am planning on posting a complete discussion next weekend, 27-29 March. Will it still be the “same atmosphere different day (SADD)”?

Ed Berry

The Great Atmospheric Recession – La-Nina Hard Times

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

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

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

Please see links below for global SST details. There have been a few notable variations during the last few weeks. For instance, in contrast to about a year ago, equatorial Pacific Ocean SSTs have been cooling from the west coast of South America to ~120W, with anomalies ~minus 1-2C extending to depths of at least 100m. There has also been some warming from the far west central into the southwest Pacific, with anomalies ~plus 1-2C and totals approaching 30C. While weakened, the negative PDO signal is still present.

Overall, this is the time of year when the annual cycle of tropical ocean SSTs may be the most important in terms of ENSO. Whether or not the equatorial east Pacific Ocean cooling is "telling us something ", is unclear. Regardless, in my view the global atmosphere has generally been leading the Nino SSTs (including the official ONI) since at least December 2006. As discussed below, the La-Nina characteristics of the atmosphere remain well established. Variations understood (ex., 2007-08 and other events); at this point I would be surprised if I am not typing about La-Nina circulation issues a year from now (hopefully in a much better main streamed graphical medium than these discussions!).

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

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

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

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

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/index.primjo.html (link 19)

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

From the global ocean-land-atmosphere dynamical system perspective, our quasi-stationary La-Nina circulation base state is quite pronounced and probable to persist “until further notice (UFN)”. However, the subseasonal component interfacing weather and climate is about as complicated as it can get. While I do feel relatively comfortable about the details about the dynamical processes involved (within the WB (2009) GWO framework), and confident about the probable synoptic variations for at least the next several weeks, it is a challenge to write about. Obviously, transition seasons add difficulty. I am only going to “broad-brush”.

Enhanced tropical convective forcing is occurring across multiple regions of the globe. The most important tied to La-Nina is the area centered ~0/140E, extending from the far eastern Indian Ocean into the southwest Pacific. Generally diurnal convection continues across northern South America, and rainfall is anomalously intense over equatorial and South Africa. Rigorous daily monitoring of rapid baroclinic wave packets/zonally oriented Rossby wave energy dispersions (RWDs) interacting with tropics tells me the Western Hemisphere tropical signal was forced by the extratropics. In fact, through 13 March a greater than 1 sigma MJO projection was depicted in octant 8 of WH (2004) phase space (removing ENSO). In some sense, one can argue that there is a weak “GWO driven MJO”.

Coherent modes Hovmollers and other tools suggest the “140E tropical forcing” is drifting slowly west. Similar to many events earlier this year, a convectively coupled Rossby mode may be contributing to the westward movement. I do think there will be consolidation of this convection with the eastward propagating Western Hemisphere signal in the region of ~100-120E during the next couple of weeks. For reasons, I suspect much of the western and central equatorial Indian Ocean will again be “by passed”. The consolidation will help to maintain/reload La-Nina.

Through 12 March, while tilted toward the La-Nina attractor, there is only a weak projection on the WB (2009) measure of the GWO. Does this mean there is little information to be gained from it? The astute reader will answer, “absolutely not!” Once again there is a “La-Nina equilibrium of sorts” involving various time evolving components of the earth-atmosphere AAM budget (see plots) forcing a weak projection (for now).

For the last ~30 days a large GWO variation of roughly 3 sigma involving first eddy poleward AAM transports then strong surface torques worked to add westerly wind flow to the global atmosphere. Zonal mean contributions of anomalous westerly wind flow were ~10N and ~45N (responses in the Southern Hemisphere were much weaker). The former led to a sickly looking subtropical jet (STJ) into the southern USA (did bring needed precipitation to Texas) and latter a northward shift of the zonal mean storm track. However, intense anomalous zonal mean easterly wind flow also shifted poleward to ~30N, having weekly means ~12m/s. So, once again, anomalous midlatitude ridges are present across the Northern Hemisphere extratropics, similar to the positive phase of a Branstator (2002) circumglobal teleconnection. Phase 2 of the GWO 250mb snr psi composite anomaly plots loosely depict the global circulation, especially the extratropics.

Overall, like that seen during the 2007-08, and typed so many times this cold season, there is nice interhemispheric (mainly northern; austral warm season) meridional symmetry of zonal mean zonal wind anomalies. Furthermore, consistent with the tropical forcing, animations of upper tropospheric daily mean vector wind anomalies do suggest the Indian Ocean (west Pacific Ocean) anticyclones (cyclones) are in the process of getting reestablished. Phase 4 of the MJO snr 250mb psi composite anomaly plots best depicts tropical circulation anomalies. In general, with variations, phases 4-5 of these MJO composites may best represent the tropics UFN.

The whole above spiel simply tells us the global circulation is “classic La-Nina”, and is probable to continue, again, UFN. I do expect the GWO to resume its orbit in phase space, roughly octants 1 to 4 then back with periods perhaps ~20-30 days. Similar to a year ago, these orbits may spiral upward. However, an important difference between this boreal winter and last year is the lack of relatively robust slower subseasonal variations including MJOs compared to a year ago.

Utilizing the GWO and MJO snr composites for ~week 1-4 predictions may be quite challenging in these hard times. This is where “Rottweiler experience and understanding of this stuff” is needed. Loosely, focusing on the lower 48 states, I think we are going to continue seeing synoptic alternations between east Pacific Ocean troughs/western and central states ridges/east coast troughs with western troughs and southeast states ridges. The latter may become preferred heading through spring (was a year ago with the subseasonal activity), and the storm track is probable to remain shifted north.

Weather ramifications are understood, including the likelihood and expansion of worsening drought conditions (rangeland wildfires, dust storms, etc.) across the central and southern High Plains. If any “miracles” can happen (ex., resumption of MJOs) and stronger STJs can be directed into the USA Desert Southwest, that will help to mitigate at least some of the dryness. The latter could also help other parts of the country experiencing drought. The Pacific Northwest is likely to remain excessively wet for at least the next 2-4 weeks.

I trust the expertise of the appropriate meteorological agencies to alert the public of additional weather hazards worldwide. An elevated risk of tropical cyclones is probable perhaps both sides of the equator in the region of Indonesia and northern Australia weeks 1-2. In fact, that concern may focus from the northeast coast of Australia into the region of the South Pacific islands, given warm SSTs, weakly anomalous surface westerly winds and other reasons.


Appendix


All presentations from the 24 February 2009 GWO workshop are available via anonymous ftp. If you have not received information on how to retrieve these, let me know. There was excellent attendance at this day-long event, and feedback was strongly positive. We appreciate all the support!

Links to CPC and PSD ENSO discussions, and a new experimental forecast technique involving a coupled LIM (3rd link below):

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

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

http://www.cdc.noaa.gov/forecasts/clim/

The following are links to information about the stratosphere and other nice monitoring tools:

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

http://code916.gsfc.nasa.gov/Data_services/met/ann_data.html (new stratosphere link!)

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

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

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

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

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

The WB (2007) paper on the GSDM has been published in the February issue of MWR. The first of a two-part paper, where WB formally introduce the GWO (WB (2009)), is (still) awaiting publication in MWR. A pdf of an in press version can be downloaded from the following link:


http://www.cdc.noaa.gov/map/clim/wb08_revised_final.pdf



In addition to the subseasonal snr composite anomaly plots, we would like near real-time discussions with “weather maps” to become a routine part of the ESRL/PSD GSDM web site sometime soon. Part-2 of our GWO paper will discuss the latter. We want to emphasize notions such as global-zonal mean-regional scale linkages as well as forcing-response-feedback (with subsequent interactions) relationships. An important purpose is to provide a dynamical weather-climate linkage framework to evaluate the numerical models in a sophisticated manner as part of a subseasonal (and any time scale) forecast process, in addition to a climate service for all users. Relying on the numerical models alone is a cookbook, extremely unscientific, and makes the Rottweiler VERY angry!

I will not be able to post another discussion until the weekend of 27-29 March due to covering operational overnight shifts. It may just be the “same atmosphere different day (SADD)” anyway!

Ed Berry

AAM Rally in a Bear Atmosphere

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

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

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

Please see links below for global SST details. Little overall change has occurred during the past week. The anomalously cool SSTs recently observed across much of the North Tropical Atlantic Ocean and portions of the Caribbean may have had a significant contribution from extratropical processes. For instance, cold surges accompanying digging troughs into Europe have plunged well south into the tropics during much of the winter, as have similar surges off the USA east coast. The cold front that accompanied the eastern states snowstorm earlier this week is nearing the north coast of South America as I type.

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

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

http://www.pmel.noaa.gov/tao/jsdisplay/

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

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

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

While displaced toward low AAM in phase space, a large, roughly 3 sigma variation of the WB (2009) measure of the global wind oscillation (GWO) has been occurring since roughly 12 February. This behavior has been the dominant component of the subseasonal weather-climate dynamical system within a well established La-Nina base state. The orbit has involved approximately octants 1-4, having a magnitude similar to those seen during boreal fall 2008. The dynamical processes explained by the GWO have been working to try to bring global westerly wind flow back to normal, somewhat analogous to Le Chatelier’s Principle for chemical equilibrium. However, I also think we are seeing an atmospheric variation analogous to a bear stock market rally, and, unfortunately, Le Chatelier’s principle cannot be applied to the latter.

More specifically, the current GWO orbit in phase space is relatively “clean’, following the chain of events outlined in WB (2009). This dynamical measure of the global circulation also provides some quantitative evidence that the extratropics have been recently forcing the tropics. Broadly, there was first strong poleward AAM transport during the first half of February centered ~35N, followed by a strong positive global frictional torque, then global mountain torque. Please see AAM plots for details. Presumably involving the eddies and mass circulations (on our list to quantify along with real-time diagnostics), downward transport of anomalous subtropical easterlies ramped up the frictional torque. Anomalous high surface pressures then increased the global mountain torque. Through 4 March, global relative AAM tendency is again becoming negative, forcing the GWO toward Octant 1 while orbiting around the La-Nina attractor.

Primarily zonally oriented Rossby wave energy dispersions (RWDs), observed during the past several weeks, linked to these complicated dynamical processes have subsequently impacted the deep tropics. For example, the upper tropospheric anomalous twin subtropical cyclones connected with La-Nina were forced west of the Dateline. Intense zonal mean easterly wind flow anomalies that have been dominating the subtropical atmospheres have also weakened a bit, while shifting poleward. In fact, there is even anomalous zonal mean westerly wind flow across the northern subtropics (~5m/s at 200mb), regionally in the Western Hemisphere.

All of these processes have been trying to “jump start” the atmosphere. Regional scale responses have included progression of the PNA central Pacific Ocean ridge-USA west coast trough pattern, and an amplifying central North Atlantic Ocean ridge (not the NAO; this is a dipole of anomalies). As expected given the GWO orbit, these synoptic evolutions can be seen fairly well from looking at phases 1-4 of the GWO 250mb snr PSI composite anomaly plots.

Consistent with our quasi-stationary La-Nina base state, tropical convective forcing remains loosely focused on Indonesia, centered ~0/120E. Per above, a “poor excuse” of a subtropical jet extends from the Northern Hemisphere twin subtropical cyclone near the Dateline into the USA Desert Southwest (with lots of mid/upper tropospheric cloud cover). At least diurnal convection continues across tropical South America and Africa. Retaining the interannual signal, the WH (2004) measure of the MJO has ~1.5-2 sigma projection in octants 4-5 of phase space. Subtracting out ENSO, the signal is much weaker. In this case, the latter is more realistic (need to understand how to interpret any index; the Rottweiler is always watching!), the MJO signal is negligible. Phases 4-5 of the MJO snr 250mb PSI composite anomaly plots best represent tropical circulation anomalies, as they generally have since boreal fall 2008.

Where does the atmosphere go from here? Unlike the current financial markets, relative AAM may have found a “bottom” for the boreal 2008-09 cold season. This behavior would be consistent with that seen a year ago. As I have already typed in past postings, La-Nina circulation anomalies are likely to linger well into spring (at least), with synoptic variations tied to GWO. Synoptic responses shown by the GWO snr 250mb PSI (and other variables) composite anomaly plots for ~phases 8-1 to 4-5 shifted toward low AAM are probable “until further notice”. These will work with the seasonal cycle. This suggests a preference of more progressive western and central states troughs. However, like the stock market volatility (and different from a year ago), there will be deviations including eastern USA troughs and transient ridges from Hell.

Numerical model performance has suffered significantly during the last several weeks literally due to the GWO. I think their forecasts for the next ~5 days are useable (predictability always decreases during transition seasons). During weeks 2-3, the added subtropical westerly wind flow (per above) may help to extend the East Asian jet (shifted north) into the western USA. That may contribute to more energetic progressive troughs including their expected possible high impact weather. This does include warm sector severe local storms (remembering tropical moisture transports issues through the Gulf of Mexico) and cold sector (thunder) snowstorms with individual baroclinic cyclones. However, drought conditions are probable to continue intensifying across the central and southern High Plains.

I trust the expertise of the appropriate meteorological agencies to alert the public of additional weather hazards worldwide. Notable events continue. Locations centered on Indonesia and working into the Philippines are likely to get hammered with intense-severe tropical thunderstorm activity for at least the next 2-4 weeks. An elevated risk of tropical cyclone activity is probable around the north coast of Australia the next 1-2 weeks.

Appendix

All presentations from the 24 February 2009 GWO workshop are available via anonymous ftp. If you have not received information on how to retrieve these, let me know. There was excellent attendance at this day-long event, and feedback was strongly positive. We appreciate all the support!

Links to CPC and PSD ENSO discussions, and a new experimental forecast technique involving a coupled LIM (3^rd link below):

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

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

http://www.cdc.noaa.gov/forecasts/clim/

The following are links to information about the stratosphere and other nice monitoring tools:

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

http://code916.gsfc.nasa.gov/Data_services/met/ann_data.html (new stratosphere link!)

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

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

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

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

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

The WB (2007) paper on the GSDM has been published in the February issue of MWR. The first of a two-part paper, where WB formally introduce the GWO (WB (2009)), is (still) awaiting publication in MWR. A pdf of an in press version can be downloaded from the following link:

http://www.cdc.noaa.gov/map/clim/wb08_revised_final.pdf

In addition to the subseasonal snr composite anomaly plots, we would like near real-time discussions with “weather maps” to become a routine part of the ESRL/PSD GSDM web site sometime soon. Part-2 of our GWO paper will discuss the latter. We want to emphasize notions such as global-zonal mean-regional scale linkages as well as forcing-response-feedback (with subsequent interactions) relationships. An important purpose is to provide a dynamical weather-climate linkage framework to evaluate the numerical models in a sophisticated manner as part of a subseasonal (and any time scale) forecast process, in addition to a climate service for all users. Relying on the numerical models alone is a cookbook, and extremely unscientific!

I will attempt to post a discussion the weekend of 14-15 March 2009.

Ed Berry