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Tropical Storm Gabrielle Discussion Number   8
NWS National Hurricane Center Miami FL       AL082019
1100 AM AST Thu Sep 05 2019

Gabrielle is struggling due to persistent southeasterly shear. The
low-level center is completely exposed and has become quite
elongated, and the nearest deep convection is displaced almost
60 n mi to the north. And yet, ASCAT-A and B data at 1200 UTC
revealed that the winds have not yet decreased. Both passes showed
winds of 40-45 kt in the northwest quadrant of the cyclone, so the
initial intensity is held at 45 kt.

For the next 36 h or so, Gabrielle will remain in a very unfavorable
environment, and the wind shear is actually expected to increase
according to SHIPS diagnostics from the GFS and ECMWF models. Beyond
that time, the shear is forecast to decrease and Gabrielle will have
a window in which it could strengthen over the weekend. By early
next week, the cyclone is expected to move over much colder SSTs and
will likely begin the process of becoming post-tropical, so further
strengthening is unlikely. The new NHC forecast is generally close
to the previous one, but now allows for some slight short-term
weakening of Gabrielle, given the hostile current environment.

Almost no change was required to the track forecast, which is
merely an update to the previous advisory. Gabrielle should move
generally northwestward toward a weakness in the subtropical ridge
for the next 3 or 4 days before it recurves ahead of a deep-layer
mid-latitude trough approaching from the northwest by the end of the
forecast period. The NHC forecast lies near the middle of the track
guidance envelope.

FORECAST POSITIONS AND MAX WINDS

INIT  05/1500Z 22.8N  35.5W   45 KT  50 MPH
 12H  06/0000Z 23.8N  36.4W   45 KT  50 MPH
 24H  06/1200Z 25.5N  38.1W   40 KT  45 MPH
 36H  07/0000Z 27.4N  40.0W   40 KT  45 MPH
 48H  07/1200Z 29.4N  42.3W   45 KT  50 MPH
 72H  08/1200Z 33.0N  47.0W   55 KT  65 MPH
 96H  09/1200Z 37.0N  48.0W   60 KT  70 MPH
120H  10/1200Z 42.0N  42.5W   55 KT  65 MPH

$$
Forecaster Zelinsky

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