No Dancing – SSTs Responding to La-Nina; Increasing Risk for USA Extreme Winter Weather Weeks 2-5

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

The 91-day signal to noise ratio (snr) anomaly composites are currently centered on 10 November due to technical issues. This should be resolved soon meaning resumption of daily updates, and will have minimal impact on these assessments. Please see product descriptions. WB (2008), part-1 of a 2 part paper where the GWO is formally introduced, is in press for MWR publication. There is a link in the Appendix to download the manuscript.

Remember that these discussions are part of an experimental effort linking weather and climate. Until this work is formalized at the national level, many important scientific issues we are easily well aware of cannot be addressed. Stated another way, it is nearly impossible for me to talk about “everything” in these postings. Also, there are tentative plans to have a one-day workshop on the WB (2008) GWO concepts ~February 2009 in Boulder. Stay tuned for details.

The warmest SSTs globally extend from southern Indonesia to the north coast of Australia having totals at least 29-30C and positive anomalies in excess of 2C ~10-15S. The Indian Ocean has cooled as has the TNWP. The former is from severe tropical convection and latter East Asia cold surges. Significant negative anomalies extend from ~140W to at least 160E within 10 degrees of the equator. Daily anomaly magnitudes on 21 November were ~minus 1-2C with totals well under 29C. In fact, responding to continued enhanced trades since mid September, latest 5-day averaged TAO buoy data shows negative SST anomalies 0.5C and lower from ~140W to 160E within 2 degrees of the equator (please look up the relevant Nino regions).

Yes, we understand the subsurface issues and the concerns raised by the PDO crowd, latter measure projecting on an extreme negative phase. Regardless, there is always constant interaction between the global atmosphere and SSTs. The global tropical SSTs contributed to forcing the atmosphere into the low AAM side of GWO phase space (La-Nina characteristic) perhaps as early as December 2006. With variations, this has not changed. Currently, the equatorial central and eastern Pacific Ocean SSTs are responding to a global circulation state favoring coolness in those regions. This is why measures such as Nino 3.4 to define “ENSO neutral” have limited scientific defensibility, let alone basing seasonal forecasts on them.

Referring to my title, just like the 1974 Ali-Foreman fight when the former did not dance after round 1, I am not clowning around with phrases such as “El-Viejo”, “witch”, “Rottweiler statements”, etc. for this discussion. The earth is not flat, center of the universe, etc., meaning care should be exercised thinking that any weather-climate phenomena such as ENSO has to follow a "classic cycle" (ex., Rasmussen and Carpenter (1982)). While encore events tend to be weaker (there are very important sample size issues), everything I and others understand tell us, from the global ocean-land-atmosphere perspective monitoring subseasonal variability, La-Nina is back.

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

The subseasonal global circulation variability leading to the above appears that it will have significant implications for world weather including the USA well into at least December. Again, I do want to keep the rest of this “treatise” relatively concise.

Tropical convective forcing is currently centered ~5N/100E extending from the southeast Arabian Sea to north of New Guinea. Enhancement is also present from southern Indonesia to east of Australia, along a westward displaced SPCZ. The tropical forcing does have a MJO component to it, projecting ~1.5sigma in octant 5 of WH (2004) phase space, ~2sigma in octant 4 with the interannual component left in. There has been eastward propagation of ~5-6m/s along the equator for the past couple of weeks. However, just as the last MJO was truncated, I think this one will also be. During the next 1-2 weeks, a large portion of this severe rainfall is probable to shift east-southeast along the SPCZ impacting northern and eastern Australia. Impacts are also likely from southern India to the Philippines.

The large variation of the WB (2008) measure of the GWO is currently the most robust weather-climate signal. Global relative AAM (plots updated through 20 November) is ~1 standard deviation (1 AMU) above the R1 data climatology, working with ~ plus 40 Hadley positive global tendency. The former may be the highest since about a year ago.

The astute reader may now ask how this can be if I am arguing La-Nina is back. Of course, given that the GWO is red noise (stochastic), with the large signal "something else" can happen meaning the point of this whole discussion (La-Nina) may be a poor assessment on my part. However, since I think we are seeing a repeatable event (more said below) within an emerging quasi-stationary La-Nina base state, odds are with me. Time will tell. What the large GWO signal means is global westerly wind flow has increased, much of that occurring in the subtropical atmospheres where 200mb zonal mean zonal wind flow anomalies are ~2-5m/s. The dynamical processes contributing to this have come from the global surface torques, with the mountain ~plus 30 Hadleys and frictional ~plus 20 Hadleys.

This is the point where a real-time live discussion with “maps and plots” is needed. In a sense, a repeatable variation of the 3sigma October GWO orbit in phase space is in progress. Much of the positive frictional torque is coming from the extratropics linked to poleward and downward propagation of anomalous upper tropospheric zonal mean easterly wind flow. I can also link the components of the current positive clustered mountain torque to this. All of this has involved coupled complicated interactions with tropical-extratropical Rossby wave energy dispersions (RWDs) interacting with the baroclinic eddies. At times, during the last several weeks, there have been well defined projections onto a positive phase of the Branstator (2002) circumglobal teleconnection (anomalous midlatitude ridges). Bottom line, the global wind signal is dominating the tropical convective forcing.

Since at least mid September there has been a strong zonal asymmetry of tropical upper tropospheric circulation anomalies consisting of twin Indian Ocean (west central Pacific) anticyclones (cyclones), typical of a quasi-stationary La-Nina base state. Per animations there was an attempt of subtropical transition to an opposite phase earlier this month, and there may be a feeble attempt as I type, latter across the Indian Ocean. However, going along with the sudden crash in AAM tendency and AAM I am expecting during the next 1-2 weeks, the Indian Ocean upper tropospheric anticyclones, etc., are likely to return. I do expect Indian Ocean tropical forcing to become expansive during December, then perhaps focusing ~100-120E. Another bottom line is what we may be seeing is an “AAM rally in a bear atmosphere”.

Regionally, a synoptic response across the Asia-North American sector is the extending East Asian jet as I type. Phases 4-5 of the GWO 250mb snr streamfunction composite anomaly plots best represent the extratropics. Phases 3-4 of the MJO 250mb snr streamfunction composites generally depict the zonally asymmetric tropical circulation anomalies discussed above. I have not been accurate on frankly white noise details during the last few weeks. Nevertheless, all of the above writing is on track with my notion since about mid October of another large GWO 4-5 to 8-1 evolution within a La-Nina base state during the end of this month leading to a December central USA cold regime.

Consistent with a complete forecast process, models such as the ESRL/PSD ensemble and recently the NCEP/GEFS into early week-3 are starting to catch on. I am concerned the largest negative surface air temperature anomalies may be shifted farther west (linked to Indian Ocean forcing) toward the Rockies and Plains rather than ~95W (per past discussions), particularly during the latter half of next month. Even portions of the USA Pacific Northwest may experience Arctic air during December. Implied is an active southwest flow storm track (with variations) on the Plains.

Loosely, December renditions of phase 3 (not available on-line, yet) of both the GWO and MJO 250mb snr streamfunction composite anomaly plots may represent next month. Of course, unpredictable rapid variations in GWO phase space will occur. In any event, I respectably offer that the official USA forecasts for at least December 2008 and DJF 2008-09 “may be in trouble” (seasonal mean issues understood). The anomalous warmth suggested across portions of the Deep South for DJF may be okay. There should be more of a “La-Nina flavor”.

Weather ramifications have already been suggested. The extended North Pacific Ocean jet/split flow pattern across the USA week-1 per models giving an active southern storm track is likely. This will cause holiday travel problems starting around Thanksgiving, while also giving much needed rainfall to fire-ravaged California. Weeks 2-5 is per above. Any concerns sensitive to the real possibility of extreme cold air temperatures perhaps focused from the Northern Rockies into mid/upper Mississippi Valley and possibly extending into the western Ohio Valley may want to “plan”. The above mentioned storm track may get better defined going through December. Depending on tropical moisture transport through the Gulf of Mexico, severe winter weather including blizzard conditions and intense thundersnow may impact the northern and central Plains. Other weather responses should be understood, including impacts on Christmas travel.

Weeks 1-2 for the tropics are also per above. There is a strong westerly wind event from the central Indian Ocean into Australia, and that could increase the risk of tropical cyclones in that region. Diurnal thunderstorm activity tied to the GWO may intensify across tropical South America weeks 1-2. Tropical South Africa into the South Indian Ocean may see a rapid increase in rainfall by weeks 2-3, only to expand in coverage and extend eastward weeks 3-5, perhaps centered ~0/100-120E. Finally, the warm southwest Pacific Ocean may become the “wild card” this boreal cold season.

Please see the latest official tropical cyclone forecasts for all basins. I trust the expertise of the appropriate meteorological centers to alert the public of additional weather hazards worldwide. Active regions have been occurring during the last week, including the cold and stormy situation around Europe.

Appendix

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/

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

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

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 (2008)), has been accepted for publication MWR. A pdf of the 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 hope near real-time discussions with “weather maps” will 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! I plan on posting a discussion the weekend of 29-30 November.

Ed Berry