[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 041454
TCDAT3

Tropical Storm Gabrielle Discussion Number   4
NWS National Hurricane Center Miami FL       AL082019
1100 AM AST Wed Sep 04 2019

Gabrielle appears better organized on satellite imagery
this morning with the low-level center moving a little more
underneath the convection.  In addition, a large curved band has
become better defined in the northern semicircle.  The initial wind
speed is increased to 45 kt, which is consistent with a
just-received ASCAT-C pass of 40-45 kt.

The initial motion estimate is 320/8.  For the next 5 days,
Gabrielle is forecast to move generally northwestward toward a break
in the Bermuda-Azores high pressure ridge located between 40W-50W
longitude. An increase in forward speed in a few days is expected
due to the gradient between an upper-level low to the west and the
ridge to the northeast. The official forecast track lies slightly to
the east of the previous forecast in the short term, and then is
very close to the previous NHC track in days 3 to 5.

Gabrielle is expected to remain in a marginal environment during the
next 2 to 3 days, with moderate southerly to southwesterly wind
shear, low values of mid-level relative humidity and SSTs near
26-27C. No change in wind speed is predicted during the first two
days.  Thereafter, some strengthening is possible as Gabrielle moves
on the northeast side of the upper-level low concurrent with the
cyclone moving over warmer water.  This is a typical situation for
intensification, so the forecast wind speed is raised slightly at
days 4-5. The intensity forecast is fairly consistent with the bulk
of the typically reliable intensity models.


FORECAST POSITIONS AND MAX WINDS

INIT  04/1500Z 20.5N  33.8W   45 KT  50 MPH
 12H  05/0000Z 21.0N  34.5W   45 KT  50 MPH
 24H  05/1200Z 21.9N  35.6W   45 KT  50 MPH
 36H  06/0000Z 23.1N  36.9W   45 KT  50 MPH
 48H  06/1200Z 24.6N  38.4W   45 KT  50 MPH
 72H  07/1200Z 28.6N  41.7W   50 KT  60 MPH
 96H  08/1200Z 32.5N  45.5W   55 KT  65 MPH
120H  09/1200Z 36.5N  47.5W   55 KT  65 MPH

$$
Forecaster Blake/Hagen
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