Tropical Storm Gabrielle Forecast Discussion Number 20

By | September 8, 2019

Issued at 500 AM AST Sun Sep 08 2019


000
WTNT43 KNHC 080832
TCDAT3

Tropical Storm Gabrielle Discussion Number  20
NWS National Hurricane Center Miami FL       AL082019
500 AM AST Sun Sep 08 2019

Gabrielle has become a little better organized overnight.  The
storm now has well-defined curved bands, especially to the south
of the center, with some evidence of an inner core trying to form.
The initial intensity is nudged upward to 50 kt, which is between
the Dvorak classification from TAFB and the latest satellite
consensus estimate from the CIMSS at the University of Wisconsin.
Earlier ASCAT data revealed that Gabrielle is a compact storm with
its tropical-storm-force winds only extending out to about 60 n mi
from the center.

The tropical storm is gradually turning to the right, with the
initial motion estimated to be northwestward at 11 kt.  The system
is located near the southwestern periphery of a mid-level ridge
centered near the Azores, and it should be moving around the
western side of that ridge later today and tonight.  This should
cause Gabrielle to turn northward with some increase in forward
speed during that time.  An even faster northeastward motion is
expected on Monday and Tuesday as Gabrielle, or its post-tropical
remnants, become embedded in the mid-latitude westerlies.  The
track models are in fairly good agreement, and only minor
adjustments were made to the previous forecast.

Gabrielle could strengthen a little more today while it remains
over warm water and in generally favorable atmospheric conditions.
However, the combined influences of increasing southerly shear and
cooler waters should end the chances of intensification on Monday.
The global models are in agreement that Gabrielle should become
extratropical when it merges with a cold front that is associated
with Post-Tropical Cyclone Dorian in a little more than 2 days.
The extratropical low is expected to gradually weaken and
ultimately dissipate in 4 to 5 days.  The NHC intensity forecast is
largely an update of the previous one and in line with the majority
of the intensity guidance.


FORECAST POSITIONS AND MAX WINDS

INIT  08/0900Z 32.7N  48.6W   50 KT  60 MPH
 12H  08/1800Z 34.3N  49.2W   55 KT  65 MPH
 24H  09/0600Z 37.1N  48.5W   55 KT  65 MPH
 36H  09/1800Z 40.1N  45.7W   55 KT  65 MPH
 48H  10/0600Z 42.7N  41.0W   55 KT  65 MPH
 72H  11/0600Z 48.1N  28.6W   45 KT  50 MPH...POST-TROP/EXTRATROP
 96H  12/0600Z 56.0N  10.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
120H  13/0600Z...DISSIPATED

$$
Forecaster Cangialosi

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