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TROPICAL STORM GRACE DISCUSSION NUMBER   8
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072015
500 AM AST MON SEP 07 2015

Deep convection has redeveloped near the center of Grace overnight,
and an earlier SSMI microwave overpass showed that the convection
was organized in a couple of bands around the center.  There are
indications in geostationary satellite imagery that the shear is
beginning to increase as the cirrus outflow has become restricted
over the western portion of the system.  The initial wind speed
remains 45 kt, which is in agreement with subjective Dvorak
satellite intensity estimates from TAFB and SAB.  Little change in
strength is expected today.  Environmental conditions are forecast
to become less favorable by tonight as westerly vertical wind shear
increases and dry mid-level air over the tropical Atlantic impinges
on the circulation.  The shear is forecast to increase to 20-30 kt
by late Tuesday, and weakening is expected to begin by that time.
The NHC intensity forecast is close to the LGEM model and the
intensity consensus.  Given the strong southwesterly upper-level
winds expected near the eastern Caribbean late in the period, it is
quite possible that Grace will degenerate to a tropical wave
before it reaches the Lesser Antilles.

Grace continues to move westward or 275/14 kt.  The tropical
cyclone is forecast to move generally westward to the south of a
large mid- to upper-level ridge over the central Atlantic. The
model guidance is in good agreement on this scenario and the NHC
forecast is once again essentially an update of the previous NHC
advisory.  The new track forecast is close to the multi-model
consensus.


FORECAST POSITIONS AND MAX WINDS

INIT  07/0900Z 13.5N  33.9W   45 KT  50 MPH
 12H  07/1800Z 13.7N  36.1W   45 KT  50 MPH
 24H  08/0600Z 13.9N  39.1W   45 KT  50 MPH
 36H  08/1800Z 14.2N  42.2W   45 KT  50 MPH
 48H  09/0600Z 14.7N  45.4W   40 KT  45 MPH
 72H  10/0600Z 15.5N  51.6W   35 KT  40 MPH
 96H  11/0600Z 16.2N  57.2W   35 KT  40 MPH
120H  12/0600Z 16.8N  62.5W   30 KT  35 MPH

$$
Forecaster Brown

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