Thursday, December 08, 2005

Models Slowly Catching On

What I posted on 8 December still looks to be on track. At this time tropical convective forcing continues to become more robust with the centroid around 5 degrees north latitude/110-120 degrees east longitude (5N/110-120E notation for future posts). There has also been fairly rapid intensification of additional thunderstorm clusters across the equatorial Indian Ocean (IO), which may help to shift the general forcing farther west during the next 1-2 weeks. Finally, partially linked to a fairly weak rapid eastward propagating convective signal across the western hemisphere, a smaller flare-up exists across warm SSTs near 10-15S/160W. Epsodic events such as the latter do contribute to subtropical jets (STJ) extending into the southwestern USA.

The extratropics continue to respond to the tropical forcing, with twin subtropical anticylones becoming established across the IO (a signal of westward shifting), in addition to those across Indonesia. This development continues to support the previous notion that the current north Pacific polar jet will break through the present east Pacific/western USA ridge by early next week (a major forecast problem for the west coast). Retrogression of the ridge position to around 140W by roughly late next week into next weekend would then be most probable, favoring a trough and possible storm development across the Rockies and Plains. Again, uncertainty continues high due to other behaviors such as nonlinear feedback issues with the current blocking present at the higher latitudes.

I have been noticing a few more models (particularly ensemble members of prediction systems such as the GFS and Canadian) catching on the above scenario the would seem more probable from weather-climate monitoring and dynamics. This tells me that as the responses due to the forcing become more robust, subsequent model initial conditions will begin to represent that.
To assist with understanding, perhaps the following link may be useful.

For the DDC CWA, I guess I would not expect anything "exciting" until late next week or next weekend. I will let the forecasters fill in the specifics in regard to temperature and precipitation(thanks!).

Ed Berry

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