[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 062036
TCDAT3

Tropical Storm Gabrielle Discussion Number  13
NWS National Hurricane Center Miami FL       AL082019
500 PM AST Fri Sep 06 2019

Gabrielle has become somewhat better organized during the past few
hours, with a better-defined surface circulation moving closer to a
large burst of convection in the northern semicircle.  There has
been little change in the intensity estimates, so the initial wind
speed will stay 40 kt on this advisory.

The storm continues to move to the northwest at about 15 kt.  A
large subtropical ridge to the northeast of Gabrielle is forecast to
build westward, forcing the tropical cyclone to turn west-
northwestward on Saturday.  After that time, southwesterly flow
ahead of Hurricane Dorian should turn Gabrielle quickly northward
and northeastward by early next week.  Other than some minor speed
differences, the models continue to be tightly packed.  The new
NHC track forecast is basically an update of the previous one, and
it lies near the NOAA corrected-consensus model.

Southerly shear currently near Gabrielle is forecast to relax by
late tomorrow, at about the same time that it moves over very warm
waters near 29C.  This should promote strengthening, and it is
possible that Gabrielle could intensify quickly near recurvature.
By 96 h, the cyclone should move north of the Gulf Stream, with
increasing shear. These conditions should cause a fast extratropical
transition between 96-120 h.  The new NHC prediction is raised at 48
and 72 hours, and it should be noted that quite a few models show
Gabrielle becoming a category 2 hurricane at some point during that
time.


FORECAST POSITIONS AND MAX WINDS

INIT  06/2100Z 27.9N  39.6W   40 KT  45 MPH
 12H  07/0600Z 29.3N  41.7W   45 KT  50 MPH
 24H  07/1800Z 30.8N  44.5W   50 KT  60 MPH
 36H  08/0600Z 32.2N  47.0W   55 KT  65 MPH
 48H  08/1800Z 33.9N  48.4W   65 KT  75 MPH
 72H  09/1800Z 38.5N  46.0W   80 KT  90 MPH
 96H  10/1800Z 44.0N  38.5W   70 KT  80 MPH
120H  11/1800Z 53.0N  23.0W   60 KT  70 MPH...POST-TROP/EXTRATROP

$$
Forecaster Blake
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