“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.
As expected from any slow boundary forcing on the atmosphere, global tropical and extratropical SSTs have changed little from a week ago. The warmest ocean waters have shifted south of the equator to the region of
An equatorial trade wind surge from the Dateline to
http://www.cdc.noaa.gov/forecast1/IndoPacific.frcst.html (note the initial projection)
I expanded a bit on the SSTs in an attempt to keep the rest of this discussion shorter. While in the minds of many the current weather-climate situation may appear confusing with (understandably) a significant noise factor, I do think non-trivial signals are coming back. My attribution comfort level remains okay. While the details during the last couple of weeks have not played out as “expected”, I do think the previous probabilistic predictive statements offered are loosely on track. However, my confidence in any outlooks discussed below has decreased, and also serves as an example that any good numerical model agreement does not imply high forecast confidence (yes, insert the Rottweiler!).
The MJO component of the
Phases 8-1 of the 250mb snr composite psi anomaly plots best describe the global extratropics. During ~mid October there was a large positive global AAM tendency forced by eddy poleward transports and surface torques. A response was to add weak zonal mean westerly wind flow anomalies to the subtropical atmospheres and decouple the WB (2008) measure of the GWO from the WH (2004) MJO measure. Tropical forcing then intensified across the
Subseasonal dynamical processes explained by the WB (2008) measure of the GWO are not only currently working to decrease global relative AAM, but also push the global atmosphere back toward the La-Nina attractor. For instance, updated through 6 November the computed global AAM tendency was ~minus 20 Hadleys having zonal mean contributions from negative East Asian, North American and
Regardless of how confusing the above may appear to the reader, my point is to give some evidence that the tropics and extratropics may be getting back in sync shifted toward La-Nina. I think it is probable to for both the WB (2008) GWO and WH (2004) MJO to orbit in similar octants of phase space during the next few weeks. That is, initially octant 3 then perhaps 4-5. The corresponding snr composite anomaly plots for both the GWO and MJO should represent North American weather roughly weeks 2-4.
Sources of uncertainty include the likelihood of more western Pacific Ocean and
It is possible that the “8-1 evolution” of the global circulation discussed in past postings may be occurring as I type. Regionally for North America, the
Internationally, intense to severe thunderstorm activity is likely to remain focused on
Broadly, going into boreal winter enhanced rainfall appears probable to have a quasi stationary component ~120E while shifting slowly south. The warm west central and southwest Pacific Ocean will remain the “wild card”, as there will likely be severe convective flare-ups including cyclones in those regions. The role of the MJO is unclear, and there will be tropical impacts from at least rapid ~10-20 day GWO variations that can only be captured from daily monitoring.
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.
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 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 14-16 November.