Tropical Storm Gabrielle Forecast Discussion Number 19

By | September 8, 2019

Issued at 1100 PM AST Sat Sep 07 2019


000
WTNT43 KNHC 080232
TCDAT3

Tropical Storm Gabrielle Discussion Number  19
NWS National Hurricane Center Miami FL       AL082019
1100 PM AST Sat Sep 07 2019

Microwave data indicate that Gabrielle has a well-organized central
core.  However, the convection isn't very deep, perhaps because of
dry air entrainment, with most of the convection in a band southeast
of the center.  The initial intensity is kept at 45 kt, which
agrees well with an ASCAT-B pass of 40-45 kt and the latest TAFB
fix.

The storm is moving steadily west-northwestward around the
southwestern side of a mid-level high over the eastern Atlantic.
This high is forecast to slide eastward as the westerlies intensify
due to flow around Gabrielle's southern flank in the far north
Atlantic.  Models are in very good agreement overall, but there
continues to be some speed differences.  The NHC forecast is on the
faster side of the guidance, near the NOAA corrected-consensus
guidance and the previous forecast, since the typical error in the
higher latitudes is to be too slow.

The low-shear area that was supposed to materialize in the
subtropical Atlantic near Gabrielle this weekend did not occur, and
as a result there is very little guidance suggesting that the
cyclone will become a hurricane.  The storm still has a day or two
to strengthen over relatively warm waters before shear increases
markedly, and water temperatures plummet north of the Gulf Stream.
The intensity forecast is reduced about 5 kt from the previous one
at 36-48 h, although still above the model consensus, and is similar
thereafter.  All models still show extratropical transition by 72 h
and dissipation by day 5.


FORECAST POSITIONS AND MAX WINDS

INIT  08/0300Z 32.0N  48.0W   45 KT  50 MPH
 12H  08/1200Z 33.4N  49.3W   50 KT  60 MPH
 24H  09/0000Z 35.8N  49.4W   55 KT  65 MPH
 36H  09/1200Z 38.8N  47.6W   55 KT  65 MPH
 48H  10/0000Z 41.7N  43.6W   55 KT  65 MPH
 72H  11/0000Z 47.0N  31.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 96H  12/0000Z 54.5N  13.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
120H  13/0000Z...DISSIPATED

$$
Forecaster Blake

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