typhoon_tip
(Meteorologist)
Sun May 27 2007 07:18 PM
Re: Memorial Day Weekend Area to Watch

A quick comment or two on the model outputs this Sunday morning...

As Clark was discussing and I concur; the GFS has been a bit zealous in spinning up any perturbation it can sniff out, into a meaningful tropical system this spring.

However, the Day 6 onward is interesting in the 12z ECM. The MSLP charts indicate an inverted V in the surface pressure pattern, with strong hints at cyclonic closure passing across the Panhandle of Florida by the end of Day 6. This offers some support to the prior GFS outputs.

Interesting to note that the 12z run has lost the signal for these days. The UKMET and Canadian models look more similar to the ECM so this particular GFS run appears to be an outlier... Note, the Canadian actually goes ahead develops the Atlantic season's first TC...eventually just NE of FL. The overall consensus is a little more interesting than this day's 12z GFS solution.

The deep layer shear appears to be favorable during that time period, as fairly strong antecedent ridging evolves and slowly progresses through 35N/80W, D3 - D6. That places the area of the Gulf and western Caribbean typically in a deeper layer easterly flow regime, while dropping the upper atmosphere wind velocities across these areas to light. Moreover, the trend has been to slow down the entire pattern evolution at these key latitudes, so that also somewhat prolongs this period of favorable deep layer winds, giving more time for whatever to evolve to go ahead and do so.. Because convection has had a propensity in recent days to linger and refire in that region of the western Caribbean, the establishment of any favorable governing pattern does warrant increased monitoring.

Without considering a more important intensification taking place, this all could go quite far toward adjusting the season rainfall deficits in the positive direction, going from famine to feast. This can bring a tremendous dose of obsenely high precipitable water values. ...So perhaps this would all be a good thing.

John



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