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TROPICAL SUMMARY - MONDAY JULY 27, 2015
IF IT LOOKS, SWIMS AND QUACKS ...
Low pressure system over the northeast Gulf became better organized overnight and this morning, arguably meeting the publicly posted definition of being a tropical depression, but it is not officially one
Regardless, its effects include bands of heavy rain, brisk winds, and rip currents
The forecast evolution from the Gulf to subtropical Atlantic remains complicated; in any event a zone of moisture will continue trailing back across Florida
ELSEWHERE
N/c from yesterday's tropical summary http://on.fb.me/1MvRjao in regard to the slow-moving depression in the Bay of Bengal and its threats, or the prospect of a disturbance in the east-central Pacific developing, though NHC has lowered the odds of that a bit (but still in the high range)
GULF/FLORIDA/ATLANTIC
In objectively analyzing this system, as I posted http://on.fb.me/1SJWimI this morning with additional graphics, it seemed to meet, with its increased organization, all the criteria of NHC's public definition http://1.usa.gov/1VJwjjy of a tropical cyclone.
Its circulation is no longer based on non-tropical/frontal temperature contrasts; there's a "closed" (fully circular) circulation with a well-defined center and rainbands swirling around (radar loop above); the convection i.e. rain/tstorms is not just shallow (radar indicates tops >40K feet), and it's been persistent and organized. That convection is mainly on the south side, but there have been other asymmetric/sheared systems which have officially been tropical cyclones.
There is some unwritten desire for sufficient longevity prior to designation (though there have been short-lived tropical cyclones); at the very least this could be considered a tropical low, and it's curious that even with this afternoon's tropical weather outlook update http://1.usa.gov/1Ku8aaq, the National Hurricane Center is not even acknowledging its existence - not even circling an area with a 0% chance of anything being/becoming a tropical depression now in the Gulf or later in the subtropical Atlantic.
The brisk upper-level winds from the northeast that are producing the asymmetry are fortunately also inhibiting the system from being stronger than it is, and one thing that everybody can agree on is that it would currently be of tropical depression, not tropical storm, strength (no evidence yet of 39+ mph sustained winds).
Regardless of meteorological semantics, this system already has quite a history, with the rescue situation in the Atlantic having been associated with thunderstorms during the its formative stages on Friday; and from Friday through yesterday's & today's more organized/tropical evolution, up to almost a foot of rain having been measured in western Florida along with flooding. Effects on sea and land will continue, with locally heavy rain, gusty winds, and rip currents.
Looking forward, the situation is still somewhat complicated. Models either have whatever it is moving across the northern peninsula tomorrow and emerging over the subtropical Atlantic or getting disrupted & dissipating but then reforming there, and/or a separate system spinning up, and latest satellite imagery shows a couple other Things already.
In any event, a zone of moisture will continue trailing back across Florida for a while, with additional clouds, rain and thunderstorms. |