[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 072035
TCDAT3

Tropical Storm Gabrielle Discussion Number  18
NWS National Hurricane Center Miami FL       AL082019
500 PM AST Sat Sep 07 2019

Gabrielle is still a disorganized tropical cyclone.  The center is
definitely more apparent--after its morning re-formation--but it
appears to be wobbling around within a larger oval-shaped
circulation.  Most of the deep convection is also displaced to the
west and southwest of the center due to about 20 kt of easterly
shear.  The initial intensity remains 45 kt based on earlier
scatterometer data.

The cyclone has been rotating around the northeastern side of a mid-
to upper-level low, but as this low weakens, Gabrielle is expected
to recurve around the western side of a mid-tropospheric high
located near the Azores.  Gabrielle should then get picked up by
the mid-latitude westerlies in about 48 hours, at which point it
will accelerate northeastward toward the north Atlantic.  The track
models remain in good agreement on Gabrielle's future trajectory,
but there are some speed differences, particularly between the
faster GFS and slower ECMWF once the cyclone becomes extratropical.
The updated NHC forecast splits the difference, lying near the
various consensus models, which makes it just a little west of the
previous forecast during the first 36 hours.

Gabrielle has about another 36 hours over waters that are 26C or
warmer, but the moderate-to-strong vertical shear currently
affecting the system is likely to continue, and then increase
significantly starting in 48 hours.  Therefore, only modest
strengthening is anticipated, and the NHC intensity forecast is
now near the high end of the intensity models.  All the global
models indicate that Gabrielle should become an extratropical
cyclone by 72 hours, and then it should dissipate by 120 hours.


FORECAST POSITIONS AND MAX WINDS

INIT  07/2100Z 31.9N  46.5W   45 KT  50 MPH
 12H  08/0600Z 32.9N  48.3W   50 KT  60 MPH
 24H  08/1800Z 34.9N  49.4W   55 KT  65 MPH
 36H  09/0600Z 37.7N  48.7W   60 KT  70 MPH
 48H  09/1800Z 40.8N  45.6W   60 KT  70 MPH
 72H  10/1800Z 46.0N  33.5W   55 KT  65 MPH...POST-TROP/EXTRATROP
 96H  11/1800Z 52.0N  17.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
120H  12/1800Z...DISSIPATED

$$
Forecaster Berg
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