“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.
The 91-day signal to noise ratio (snr) anomaly composites are now updated daily, centered on the date shown. 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.
The warmest SSTs globally persist ~140E within 20 degrees of the equator having totals ~29-30C but with weak anomalies. Larger positive anomalies ~1-2C are in the region of the equatorial
Bottom line, I think we may be waiting for the tropical
http://www.cdc.noaa.gov/forecast1/IndoPacific.frcst.html (note the initial projection)
I would like to keep this discussion relatively brief. The subseasonal behaviors of several components involving the earth-atmosphere-land dynamical system have not played out as I expected during the last few weeks. However, what has occurred does not surprise me. Regardless, this is an example of why rigorous daily monitoring within the WB (2007) GSDM framework is critical, and relying on the numerical models (multi model ensembles) alone is scientifically unrealistic and indefensible. Furthermore, empirical techniques employed by some synopticians to track baroclinic signals on Hovmoller diagrams as a predictive tool many weeks in advance also has little scientific merit.
Phase 4 of the WH (2004) MJO snr 250mb composite psi anomaly plots reasonably depicts the current tropical circulation. In fact, per animations of upper tropospheric daily mean vector wind anomalies, the spatial pattern of Indian Ocean anticyclones and west Pacific cyclones is similar to a couple of weeks ago. The notion offered that the opposite sense to this phase would not be as robust was correct.
So, what happened? Obviously not the coherent eastward shift of tropical forcing/circulation behavior from the Eastern into the Western Hemispheres I discussed was likely in my last several postings. Nevertheless, I do feel there is a scientifically defensible attribution, and this will be one of the many foci of WB during the next several weeks. I think dynamical processes explained by the WB (2008) measure of the GWO contributed, starting with the ~3 sigma orbit in octant 4 of phase space during mid October. Poleward AAM transports and surface torques created a large tendency working to increase zonal mean westerly wind flow in the subtropical atmospheres.
Cutting to the chase, it is possible Rossby wave energy dispersions (RWDs) linking the tropics and extratropics (fast GWO) worked to oppose this tendency, wanting to retain the global circulation in “La-Nina”. Specifically, and beyond the scope of this discussion, the latter is in reference to complex dynamics working to reduce global westerly wind flow, best represented synoptically by ~phase 3 of the WB (2008) GWO 250mb snr composite psi anomaly plots. That is, a positive phase of the Branstator (2002) circumglobal teleconnection of anomalous midlatitude ridges, observed during the boreal winter of 2007-08. Please remember that I am talking about forcing-response-feedback relationships and the not the unrealistic notions of equilibrium states (ex., Charney and DeVore 1979).
Currently, and loosely similar to about a month ago, there is an interhemispheric signal of poleward AAM flux, ~45N and 50S. The global surface torques is positive including a ~20 Hadley East Asian mountain torque (see AAM plots for details). A synoptic response has been for a cold outbreak off the coast of
What road the atmosphere takes from here is extremely uncertain, particularly for timing and details. Statements such as forecaster confidence of something like 4 on a scale 1-5 for a USA week-2 prediction of temperature and precipitation anomalies are unrealistic. The numerical models have been inconsistent, to say the least, for the last 1-2 weeks. The tropics and extratropics are still out of sync.
That said, what appears most probable is for a GWO 8-1 transition ~weeks 2-3 per above, then perhaps coupling of the tropics and extratropics across the
Weather ramifications include above (below) average temperatures returning to the eastern
It is unclear if and when the above mentioned tropical forcing will coherently shift east. However, locations from the west central into the
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. There has been an increase during the last week.
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 (2008)), has been accepted for publication MWR. A pdf of the in press version can be downloaded from the following link:
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 22-23 November.