typhoon_tip
(Meteorologist)
Sun Oct 02 2005 04:16 PM
Re: TS Stan and Other Basin Activity

Hi HankFrank!
Check this out:
"A BROAD AREA OF SHOWERS AND THUNDERSTORMS...ASSOCIATED WITH A
WESTWARD-MOVING TROPICAL WAVE AND AN UPPER-LEVEL LOW...IS CENTERED
A FEW HUNDRED MILES EAST OF THE CENTRAL BAHAMAS. ALTHOUGH
UPPER-LEVEL WINDS ARE CURRENTLY UNFAVORABLE FOR TROPICAL CYCLONE
DEVELOPMENT...THEY COULD BECOME MORE CONDUCIVE OVER THE NEXT FEW
DAYS AS THIS SYSTEM MOVES WESTWARD."

We've been watching the U/A gyre bore its way down to the surface for a few days... Interesting to say the least, considering that a large sprawling area of surface pressure is slated unanimously by the models to envelop the nations heart land by 120 hours... With the ridge in the middle latitudes of the Atlantic Ocean Basin holding firm, this implies/teleconnects to a weakness to the sea-lvl pressure field along just off the SE Coast; concurrent with an actual frontal boundary stalling in that vicinity, the models are representing this spatial orientation of features quite well.

As a result, most guidance (especially the GGEM) are attempting to develop some kind of system there. It is complicated because there are tropical/hybrid type contaminations to any cyclogenisis behavior, depending on the respective models. Example, the ECM closes off a decent U/A low near the SE Ohio Valley by said time, while there is both an active baroclinic field along and just off the East Coast. There is also a nebulously defined tropical low in the Gulf, which “could” under ECM circumstances develop and be pulled NE out ahead of the baroclinic zone as a separate entity – that is “could”. Could be an attempt to have something base on teleconnections alone which is as you know more merely implies numerical instability; thing is, with enhanced potential, a systems often find a trigger anyway. Similarly, the GGEM seems to initiate a tropical/hybrid type circulation in the NE Gulf, but differs in that it depicts a S/W picking it up and absorbing in a system deepening more like a mid-lat cyclone near the Del Marva. …The GFS is flatter overall and doesn’t tend to much development of either…UKMET, NOGAPs all the solutions I’ve seen range similarly to this overall pattern evolution.

Obviously at these time ranges there is a question of predictive skill…But, the pattern certainly does in the least leave room for excitement later in the week and beyond.

As to Stan… I have no problem with HPC forecast for Stan, however, I am a bit concerned that the global models are tussling with the GFDL on where Stan will be after 72 hours. As you know, HPC calls for it to migrate into Mexico while never gaining latitude. I agree with limited right component for that time period, but, the conflict for me is that the barotropic models will not pick up changes in the westerlies as well as the global models do, and this does leave some room for Stan to do more of a stall and not actually make it onto land in Mexico. Granted, the lesser of the possibilities, but with early discussion topics, would add to interests in the Gulf because you have the same essential set-up with a actually fully evolved system potentially there…

Wow, very complex! Of course, this is a rough draft of thoughts for our waning tropical season. I’m sure my own opinions will vary by the end of the day…



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