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TROPICAL STORM GRACE DISCUSSION NUMBER   5
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072015
1100 AM AST SUN SEP 06 2015

The cloud pattern of the storm has changed little in organization
over the past several hours.  There are fairly well-defined curved
bands over both the northern and southern portions of the
circulation.  The deep convection is not very impressive, however,
with a limited amount of cold cloud tops and there is a dry slot in
the western semicircle.  The current intensity is kept at 40
kt, which is the average of Dvorak estimates from TAFB and SAB.
Over the next 1 to 2 days, Grace is forecast to move through a low
vertical wind shear environment with sea surface temperatures
sufficiently warm for strengthening. Thereafter, the tropical
cyclone should be encountering increasing west-southwesterly shear
associated with a large upper-tropospheric trough over the eastern
Caribbean Sea.  So, whereas intensification is probable in the short
term, Grace is likely to weaken later in the forecast period. The
official intensity forecast is the same as the previous one, and is
slightly above the latest model consensus.

Visible satellite fixes indicate that the westward motion
continues.  The steering scenario appears to be straightforward.
Grace should remain situated to the south of a subtropical ridge,
and embedded in mid- to low-level easterly flow throughout the
forecast period.  The track guidance is in good agreement on a
continued westward motion for the next 5 days, and the NHC forecast
is close to the dynamical model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT  06/1500Z 12.9N  29.9W   40 KT  45 MPH
 12H  07/0000Z 13.0N  32.0W   45 KT  50 MPH
 24H  07/1200Z 13.3N  34.7W   50 KT  60 MPH
 36H  08/0000Z 13.6N  37.4W   55 KT  65 MPH
 48H  08/1200Z 13.8N  40.1W   55 KT  65 MPH
 72H  09/1200Z 14.3N  45.3W   50 KT  60 MPH
 96H  10/1200Z 15.0N  50.5W   40 KT  45 MPH
120H  11/1200Z 15.5N  55.5W   35 KT  40 MPH

$$
Forecaster Pasch

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