“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.
Many map room plots are missing due to on-going upgrades. These issues are being worked on.
This will be short! Some warming of SSTs has occurred across the far west central equatorial Pacific Ocean (totals ~30C) as well as the west of South America. The latter may be a similar occurrence to a year ago. Overall, global SSTs remain “steady state” including ~minus 1C anomalies (warmed slightly) across all Nino regions.
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)
The global ocean-land-atmosphere dynamical system is recovering from the recent strong perturbation on La-Nina. Importantly, linked to MJO convection across the South Pacific Ocean at the time, there was large amplitude meridionally directed Rossby wave energy dispersion (RWD) across the North Pacific Ocean (with Southern Hemisphere symmetry). The RWD forced the westward shifted PNA ridge that was responsible for the severe cold outbreak centered on the Upper Mississippi Valley last week. Several diagnostics (including EP fluxes) indicate that tropospheric wave energy from this RWD has propagated into the stratosphere and a sudden stratospheric warming (SSW) may have been initiated. More said below.
The MJO signal is centered on Africa, and interactions with extratropical wave energy propagations are intensifying deep convection across the equatorial Indian Ocean. Zonal mean easterly wind flow anomalies (~5m/s at 200mb) have returned to the tropical and subtropical atmospheres. Updated through 21 January, global relative AAM is already ~2sigma below the R1 data climatology, the lowest since early October 2008. I do expect a further decline (like our recent financial markets!).
Summing up, a coupled GWO/MJO evolution from octants 7-8 the last week or so into at least 3-4 in phase space is likely the few weeks, constructively interfering with La-Nina. The global circulation shown by ~phase 3 of the 250mb snr psi composite anomaly plots for the GWO and MJO appears probable by week-2. This means our familiar pattern of anomalous midlatitude ridges, including the central Pacific Ocean ridge and a downstream trough in the region of western North America.
Regionally, the on-going discontinuous PNA retrogression is similar to that observed early December 2008. This is being forced by the current weakened La-Nina base state including residual Indonesian tropical forcing. As La-Nina reloads the next few weeks, troughing is likely to return to the Gulf of Alaska then extend into western North America. In contrast to the high confidence outlooks for the USA issued November 2008 for December, it is unclear how far southeast these next series of troughs may extend into the western USA. Should the storm track remain anomalously shifted poleward, dryness may intensify over portions of (for example) the central and southern Plains. Typical of a La-Nina base state, the Northern Hemisphere polar vortex retracted during late December, and that has been the case until very recently.
However, unusual for La-Nina, and essentially not observed during the 2007-08 cold event, a serious monitoring issue the next 30-40 days will be if a possible SSW disrupts the polar vortex. Depending on timing of behaviors, including the possibility of another MJO coming out from the Indian Ocean into the west Pacific ~weeks 3-5, there may be significant weather impacts on the USA which are currently unclear. Stay tuned. I trust the expertise of the appropriate meteorological agencies to alert the public of additional weather hazards worldwide.
The formal announcement for the 24 February 2009 one-day (~9am-5pm MST) workshop on the WB (2009) GWO has been released through various mailing lists, and is available on the ESRL/PSD GSDM web link (cited above). Let me know if you have not seen it. Please remember the intended audience of this workshop is forecasters who make daily subseasonal predictions. It will not be a “head banger’s academic ball”.
Links to CPC and PSD ENSO discussions:
The following is a link to information about the stratosphere and other nice monitoring tools:
The following is a link to NCEP model verifications (surf around for lots more)
The following is a link discussing recent global weather and related events:
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)), has been accepted for publication MWR. A pdf of the in press version can be downloaded from thefollowing link:
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! I plan on posting at least an abbreviated discussion on ~30 January 2009.