“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.
Some map room plots are still missing due to on-going upgrades. These issues are being worked on.
This will again be short! Please see links below for SSTs. Local and relatively shallow warming of equatorial Pacific Ocean SSTs has occurred west of South America, similar to a year ago. Anomalies are ~plus 1-2C. Tropical-extratropical interactions linked to the recent strong MJO and seasonal issues may be contributing. Our respectable downwelling oceanic Kelvin wave ~150m depth has propagated to about 150W. Any future impacts from the latter are unclear. Stay tuned. The warmest SSTs globally persist across the southwest Pacific, with totals ~30C in the region of New Guinea.
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)
La-Nina is reloading. Tropical convective forcing has returned to the Eastern Hemisphere with some consolidation ~0/120E while a somewhat separate region persists across the warm southwest Pacific Ocean. The MJO signal has weakened. There is little projection in WH (2004) phase space removing interannual component, but ~1.5 sigma in octant 3 (through 28 January) retaining it, reflecting the resurgence of La-Nina. Monitoring will tell if another eastward propagating signal of tropical forcing evolves. Other options include two areas such as a quasi-stationary Indonesian region concurrently with episodic southwest and west central Pacific strong to severe tropical convection.
Global relative AAM is approaching negative anomaly magnitudes comparable to the 2007-08 strong La-Nina. Updated through 26 January, AAM was ~2.5 sigma below the R1 data climatology forcing the WB (2009) measure of the GWO deeply (~2 sigma) into octants 2-3 of phase space. Zonal mean easterly wind flow anomalies have become quite strong throughout the equatorial and subtropical atmospheres, ~5-10m/s at 200mb, and up to 15m /s across Northern Hemisphere polar latitudes. The latter is a response to a sudden stratospheric warming (SSW; more said below). A loose superposition of phase 3 for both the 250mb snr psi composite anomaly plots of the MJO and GWO generally represent the global circulation, and that should continue for at least the next 2-3 weeks. This means our familiar pattern of anomalous midlatitude ridges including the central Pacific Ocean favoring a trough in the region of western North America.
Forced by (unpredictable) dynamical processes responsible for the strong west coast ridge a couple of weeks ago (see 23 January posting), a major SSW is in progress. In fact, data records going back to 1978 (see new stratosphere monitoring link in the Appendix) suggest this SSW is the strongest given this time of year. A well pronounced zonal wave number two circulation structure in the stratosphere is present, with lobes of the polar vortex across the Arctic latitudes of North America and Asia. Interacting with the La-Nina base state, the troposphere is already being impacted, and that will continue for at least the next several weeks. Large anomalies of zonal mean easterly wind flow is propagating downward into the upper troposphere of the Northern Hemisphere high latitudes as I type.
Synoptically, a possible regional-scale response is for tropospheric blocking initially across Scandinavia to retrograde through the North Atlantic and Canada then into the North Pacific Ocean during the next few weeks. The NCEP GEFS and other ensembles are starting to capture this scenario. That suggests the storm track should shift south across the lower 48 states of the USA later week-2 and perhaps continue most of February. Additional feedbacks (not discussed) from the South Pacific Ocean tropical forcing may also contribute to bringing the storm track farther south. Areas that have been anomalously dry this winter may get much needed precipitation. In fact, there may be some weather similarities to February 2008 across the USA next month. 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. An extended outline was sent today, 30 January, which should also be avialable from the ESRL/PSD GSDM web link. 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 are links to information about the stratosphere and other nice monitoring tools:
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)
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 ~7 February 2009.