Clark
(Meteorologist)
Fri Apr 15 2005 06:04 PM
Re:Subtropical low off S.C.?

It looks to be a subtropical-type storm at this time, but we're hurt by a lack of QuikScat data over the center -- it just so happened to fall in the middle of one of the data gaps.

The model phase analyses on the storm have been very interesting to date, suggesting the potential to briefly dig into the warm core realm of things. But, the validity of it depends upon how well the models are picking up the system -- and judging from the visible satellite imagery lately, it's not very big -- and the warm-core structure may be diabatically (e.g. convectively) induced, per the big guy himself (that being the man behind the phase diagrams).

It's been a really weird weather pattern over the past few days, starting with the movement of the incipient upper-low and development of a blocking pattern across the Eastern seaboard -- an upper-ridge actually built in over the NE US from the east. The structure of the system on satellite imagery & in surface analyses is not unlike a secluded structure -- not necessarily warm seclusion, but a seclusion in general. Convection has been trying to develop over the center today in a very narrow band, occasionally wrapping around, but the cloud tops are not very cold and the shear is still a bit too great -- namely on the eastern side -- for anything to happen fast.

Water temperatures, in limited spots, are near 25-26 C, subfavorable but not entirely out of the realm of possibility. In limited regions along the Gulf Stream, Max. Pot. Intensity maps suggest the potential to support up to a cat 1/2 hurricane...but if the storm were to move a whole lot, it'd get into a much weaker environment. Tropopause temperatures are around -55 C, making the difference between surface and aloft about 80 degrees C, not bad.

Most likely development, if any: subtropical structure. Likely not to move a while lot over the next few days in this blocknig regime; if anything, it should drift south. The tropical MM5 we run here in the lab (http://moe.met.fsu.edu/mm5) suggests a slow southward drift to the system, gradually dissipating in about 3-4 days. Were it to last beyond there, the strength of the ridge over the US would determine ultimate motion -- stronger would send it towards Florida (broken record, I know), weaker out to sea. The latter looks more likely, though, esp. after dissipation. We only run it at 00z each day though, so the data might be slightly old. I'll add more if there's anything new down the line...



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