Saturday, March 21, 2009

Update from the Midnight Rottweiler Rider

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.

Please see links below for global SST details. This posting will be extremely short and hopefully coherent. A significant motivation to put “something out” is the extremely interesting on-going behaviors of the weather-climate dynamical system. (note the initial projection) (link 19)

Perhaps the “miracle” I was asking for per my last posting (14 March) is evolving. Multiple regions of enhanced tropical convective forcing are occurring across the globe. These include the quasi-stationary La-Nina signal ~0/100E, a “mixed GWO/MJO component” ~10S/155E, portions of northern Southern America and South Africa. For our purposes, the most important region is across the southwest Pacific Ocean (SWP; the 10S/155E signal), representing an enhancement of the SPCZ across very warm SSTs.

A well defined subtropical wave train (~25N) progressing through Asia is interacting with the SWP forcing. Divergent outflow from this strongly enhanced rainfall has locally strengthened the subtropical jet ~25N/180. Global relative AAM calculated tendency is solidly positive ~30 Hadleys, with contributions coming largely from the subtropical atmospheres of both hemispheres. There is evidence that zonal mean equatorward AAM transport is occurring ~30N, and synoptic behaviors such as northwest-southeast tilted eddies progressing off of East Asia support that. The bottom line is we do have a respectable perturbation on La-Nina, working to increase global westerly wind flow.

A probable regional-scale response will not only be the continued strengthening of the STJ impacting the southern USA, but possibly an eventual extension of the EAJ collapsing to more western states troughs ~weeks 2-3. These troughs may extend farther south helping to dampen areas experiencing drought. A superposition of phases 7-8-1-2 (models will struggle) of the snr 250mb psi MJO and GWO composite anomaly plots may best depict this situation.

Whether or not this subseasonal event is the start of a slow transition involving ENSO is unclear. Re-iterating, numerous GWO considerations tell us the La-Nina circulation anomalies will stick around. An important monitoring issue will be to see how intense zonal mean easterly wind flow anomalies become across the Southern Hemisphere subtropics during austral winter. Weather ramifications are understood, including internationally.


All presentations from the 24 February 2009 GWO workshop are available via anonymous ftp. If you have not received information on how to retrieve these, let me know. There was excellent attendance at this day-long event, and feedback was strongly positive. We appreciate all the support!

Links to CPC and PSD ENSO discussions, and a new experimental forecast technique involving a coupled LIM (3rd link below):

The following are links to information about the stratosphere and other nice monitoring tools: (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)), is (still) awaiting publication in MWR. A pdf of an in press version can be downloaded from the following 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, extremely unscientific, and makes the Rottweiler VERY angry!

I am planning on posting a complete discussion next weekend, 27-29 March. Will it still be the “same atmosphere different day (SADD)”?

Ed Berry

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