FLHurricane.com: TD 27 Active in the SE Caribbean--here we go

...Interesting subtropical low appears to be genesizing about 1000 naut miles NE of the Leewards this morning...

First, while nothing I say is intended to preclude the possibility that a tropical depression will form of the current disturbance in the central/West Caribbean (close to Hon), it would be increasingly difficult in about another day.5. Reason being, large scale changes over Eastern N/A (which have relative certainty for trends and related teleconnections), suggest a significant expression of the +PNA is about to occur - probably lasting some time if not the rest of the month into Decembers first weeks... Hurrah, if you are a winter enthusiast, but this may also subtend a tendency for stronger SW shear components, even as far S as where any would be tropical depression #25 (or is it 26?) would materialize.

My early take on this is that it may behave similar to what we just saw happen in the eastern Caribbean... A depression will likely form near the coast of Hon...but then have difficulty intensifying "much" beyond that ranking as the surrounding environment gradually takes on these suggested increasing hostilities...

Currently on IR, there are "popcorn" cumulonimbus situated near the core of a cold U/A low, about 1000 naut miles N of the Leewards. About 300 naut miles ENE of there, we see a very baroclinic looking feature involving the lower to mid lvl fields. Having wrapped dry air into the backside (confirmed by WV), while isentropic lift associated with NW pulled WCB is a smoking gun for a frontogenic process.... But, what it interesting about this is that it is actually situated over sub-tropical type SSTs, while the NAO is neutral, tending positive in time, in tandem with said +PNA contruct set to evolve over the next 36 hours.

This will be something to watch as it slowly (most likely) migrates to the W. The +NAO, albeit subtle and or uncertain as to how intense it will ultimately become, will likely not be a very big influencer here in these nearer terms; nevertheless, it will tend to intensify the easterly component to the N of the gyre in question, and also, perhaps instantiate less capability for any wayward attempt at creating westerly shear in that area, in general. That is interesting considering that we are in the time of the year where we have about equal chances for having the shear be present in that area; perhaps much of this is a nice homage to how strong the ensuing +PNA may become, as having a very strong ridge tendency near 50W, would be a nice coupled signature for a trough evolving over the eastern 1/3 of N/A.

What all this means is that it seems higher than the average "mere 20% chance" (if you will...) that a sub-tropical low will be generated; or at least, more thermodynamically sub-tropical than the current appeal. That is to say, warm core are the surface, cold core aloft. There after, the advent of said ridge-trough couplet between the Atlantic and the intracontinental areas of eastern N/A would tend to imply a westerly drift, into a region with still warmer SSTs.

It wouldn't be a prediction for a hurricane here - I couldn't responsibly make that claim (even if a transitioned result isn't "IM"possible). But, it is an interesting time in the models because there is a lot of contention between the UKMET and GFS camps ( as just an example ), arguing over the feasibility, placemenet...etc, of a non-atypical autumnal ECS. (Drat! probably too warm this first go...)... Neat to see an ECS however, when you also have (possibly) a sub-tropical low embedded SE, but ever closer to the l/w axis the produced the ECS. . Could the l/w axis eventually interact with such a sub-tropical system ? It's a wild idea that wouldn't show up to well in the models, and of course, since those types of interaction are rare (1991 took 300 years of American technology to finally observe one, so who am I kidding)...it is more likely that the two would transpire unperturbed by eithers presents. Still, gotta love the playing field.

Edited by typhoon_tip (Thu Nov 17 2005 12:58 PM)

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