Tropical Storm VICKY Advisory pon., 14.09.

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Tropical Depression Twenty-One Special Discussion Number   1
NWS National Hurricane Center Miami FL       AL212020
900 AM CVT Mon Sep 14 2020

First-light visible satellite imagery indicates that the low
pressure system that moved off the coast of Africa a few days ago
has continued to become better organized overnight. Scatterometer
surface wind data from around 13/2200 UTC indicated that the
circulation had become better defined, and that surface winds of
25-28 kt existed in the southwestern quadrant. Since then, deep
convection has increased, and it is presumed that the surface winds
and circulation definition have increased in response, which
justifies the initiation of advisories on TD-21.

The initial motion estimate is an uncertain 355/05 kt. The cyclone
is forecast to gradually move northward today and northwestward
tonight as the depression moves around the eastern end of the
eastern Atlantic/west African monsoon trough. By Tuesday night and
continuing into Wednesday and Thursday, a west-northwestward to
westward motion along the southern periphery of a deep-layer ridge
is expected. The NHC track forecast lies down the middle of the
surprisingly tightly packed guidance envelope, and is similar to
the consensus model TVCA.

The depression is expected to be short-lived as a tropical cyclone.
Having said that, there is a narrow window of opportunity today and
tonight for the cyclone to strengthen into a tropical storm before
strong westerly shear in excess of 30 kt is forecast to induce rapid
weakening on Tuesday. The cyclone is expected to degenerate into a
remnant low by Tuesday night, and then dissipate over water on
Friday, if not sooner.

FORECAST POSITIONS AND MAX WINDS

INIT  14/1000Z 18.5N  28.3W   30 KT  35 MPH
 12H  14/1800Z 19.6N  28.6W   35 KT  40 MPH
 24H  15/0600Z 20.5N  29.6W   30 KT  35 MPH
 36H  15/1800Z 21.3N  30.9W   25 KT  30 MPH
 48H  16/0600Z 21.9N  32.8W   25 KT  30 MPH...POST-TROP/REMNT LOW
 60H  16/1800Z 22.4N  34.8W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  17/0600Z 22.8N  36.9W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  18/0600Z 23.4N  41.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  19/0600Z...DISSIPATED

$$
Forecaster Stewart/Beven