Thursday, October 18, 2007

Major Delay

Travel and other obligations preclude me from comfortably writing a complete posting useful to others. In fact, much of the latter is strongly linked to an effort to implement “operationally” at some time (hopefully reasonably soon) the objective and quantification work discussed in the Appendix. I will try to do a complete discussion during the period of 28 October-3 November.

There is no change from the reasoning about the weather-climate situation discussed 13 October. Full-disk satellite imagery and other diagnostic monitoring tools indicate that the tropical convective forcing is returning to the warm Indian Ocean, while pockets of enhancement still persist across the very warm west Pacific Ocean and around the Americas. There is some possibility for a MJO to evolve from the Indian Ocean forcing during the next few weeks.

Global relative AAM remains very low, ~2.5 AMUs per R1 data through 15 October, and a coupled GSDM Stage 1 base state to La-Nina persists. In the zonal mean anomalous easterly wind flow continues throughout the subtropical atmospheres of both hemispheres, having weekly mean magnitudes of ~3-6m/s. I think it is likely for this GSDM Stage 1 regime to continue (at least on average) through the rest of 2007, possibly longer. Hence our circulation state tilts the odds toward life cycle-1 anticyclonic wave breaking baroclinic development, including the next trough to impact the western USA (addressed below). As discussed in past postings, we need to monitor tropical convective forcing across the west central Pacific Ocean.

Regionally for the PNA sector, the positive East Asian mountain torque (~20 Hadleys) enhanced North Pacific Ocean jet is collapsing as I type. One major synoptic cyclonic baroclinic development event is currently in progress across the Upper Mississippi Valley, and I definitely favor the notion of a second development across the Southern Rockies and Plains by the end of this upcoming weekend. Models have been struggling with this second storm, and the slower and deeper solution is most probable. After a period of respite ~later week 1 into week 2 from active weather across the USA, I think this type of situation is again more likely than climatology by ~ week 3 (1-8 November).

I will be monitoring to see if a more robust western USA trough-southeast states ridge pattern becomes established by later November into December (with synoptic variations). Ramifications for particularly the central USA should be straight forward (to meteorologists) especially if there exists an Arctic cold air source and decent tropical moisture transport from the Gulf of Mexico. Translation is a stormy pattern favoring possibly significant/extreme winter weather from the Rockies into the Northern/Central Plains with heavy rainfall and thunderstorms focusing on the Ohio Valley.


An experimental quasi-phase space plot of the GSDM utilizing a time series of normalized relative AAM tendency anomaly (Y-axis) and normalized relative AAM anomaly time series (X-axis) can be found at

We call the behavior of this plot the Global Wind Oscillation (GWO). While the intent of the GSDM is to extend current thinking beyond the MJO, the purpose of the GWO is to illustrate the non-oscillatory stochastically forced component of the GSDM.

Links to CPC and PSD ENSO discussions:

These are probabilistic statements, and work is ongoing to quantify in future posts (for example, risk assessment maps, signal to noise ratio plots and shifts of probability). We hope that an opportunity will arise for us to have a dedicated web page effort to expedite more objectively, with rigor, thoroughness and verification. The WB (2007) paper on the GSDM has been published in the February issue of MWR. I will try to post another discussion ~28 October-3 November.

Ed Berry

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