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Tropical Depression Eight Discussion Number   3
NWS National Hurricane Center Miami FL       AL082017
1100 AM EDT Sun Aug 13 2017
 
The overall organization of the depression has changed little this
morning.  Visible satellite imagery and NOAA buoy data indicate
that center is located near the northwestern edge of the area of
convective banding.  In fact, nearly all of the convective banding
is located over the eastern and southeastern portions of the
circulation.  The initial intensity remains 30 kt, which is
supported by subjective Dvorak T-numbers of 2.0 from both TAFB and
SAB.
 
The depression is moving north-northwestward or 335/11 kt. The
track forecast reasoning remains unchanged. The depression is
forecast to move north-northwestward to northward around the western
portion of a deep-layer subtropical ridge during the next day or
so.  After that time, the cyclone is expected to turn northeastward
ahead of a shortwave trough that will be approaching the
northeastern United States.  As the southwesterly flow increases
over the western Atlantic ahead of the trough by 72 hours, the
cyclone should begin to accelerate northeastward.  The track
guidance is once again in excellent agreement, and only a slight
westward adjustment from the previous forecast was required.
 
The depression is currently over warm water and within a low
shear environment, but the mid-level atmosphere is relatively dry.
These conditions should allow some modest strengthening during the
next day or so.  Vertical shear is forecast to increase by late
Monday, and increase further in 2 to 3 days, which should put an
end to any additional intensification.  The system is forecast to
become extratropical in 3 to 4 days, but if it does not strengthen
it could be absorbed by an approaching trough off the Mid-Atlantic
and northeastern U.S. in a few days.  The latter portion of the
forecast continues to be based on guidance provided by the NOAA
Ocean Prediction Center.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  13/1500Z 27.4N  71.5W   30 KT  35 MPH
 12H  14/0000Z 29.1N  72.2W   35 KT  40 MPH
 24H  14/1200Z 30.7N  72.4W   40 KT  45 MPH
 36H  15/0000Z 32.5N  71.9W   45 KT  50 MPH
 48H  15/1200Z 34.6N  70.5W   50 KT  60 MPH
 72H  16/1200Z 39.0N  62.0W   50 KT  60 MPH
 96H  17/1200Z 42.5N  49.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
120H  18/1200Z 47.0N  35.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
 
$$
Forecaster Brown
 
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