[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 090232
TCDAT3

Tropical Storm Gabrielle Discussion Number  23
NWS National Hurricane Center Miami FL       AL082019
1100 PM AST Sun Sep 08 2019

Gabrielle's cloud pattern has not become better organized since
earlier today.  The central convection has become a little more
fragmented, and the center is estimated to be near the northern
side of the main area of convection.  There is a well-defined
upper-level outflow jet over the southern portion of the
circulation.  The initial intensity is held at 55 kt in agreement
with the latest Dvorak Current Intensity number from TAFB, although
this may be generous given a recent ASCAT overpass of the storm.
Gabrielle's window for additional strengthening should soon close,
since the cyclone will be over warm waters for less than 24 hours,
and the dynamical models indicate a significant increase in vertical
shear during the next day or so.  Therefore, only a slight
short-term increase in strength seems likely.  The official
intensity forecast is in fairly good agreement with the latest
corrected consensus guidance, HCCA.  By 48 hours, the global models
depict the cyclone as embedded within a baroclinic zone over the
mid-latitudes of the Atlantic.  Therefore, the official forecast
shows Gabrielle becoming extratropical by that time.  By 96 hours,
the system should become absorbed by a large low pressure system at
high latitudes.

The initial motion is northward, or 360/13 kt.  The track forecast
philosophy is basically unchanged.  Over the next 1 to 2 days,
Gabrielle should turn northeastward and accelerate as it moves
around the northwestern periphery of a mid-level high centered near
the Azores.  Later on, the cyclone should accelerate further within
the mid-latitude west-southwesterly flow.  The official forecast is
very close to the previous NHC track, and close to the corrected
consensus prediction.

Based on the ASCAT data, the 34-kt wind radii over the southern
semicircle of the circulation were increased a bit.

FORECAST POSITIONS AND MAX WINDS

INIT  09/0300Z 36.5N  49.3W   55 KT  65 MPH
 12H  09/1200Z 38.6N  47.8W   60 KT  70 MPH
 24H  10/0000Z 41.1N  44.7W   55 KT  65 MPH
 36H  10/1200Z 43.6N  40.4W   50 KT  60 MPH
 48H  11/0000Z 46.5N  35.2W   45 KT  50 MPH...POST-TROP/EXTRATROP
 72H  12/0000Z 54.5N  18.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
 96H  13/0000Z...DISSIPATED

$$
Forecaster Pasch
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