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Tropical Depression Eight Discussion Number   1
NWS National Hurricane Center Miami FL       AL082017
1100 PM EDT Sat Aug 12 2017

Late afternoon GOES-16 visible satellite images showed that the
circulation associated with the low pressure located northeast of
the Bahamas had become better defined.  Since that time, the
night-time microphysics RGB product and other infrared satellite
pictures have continued to show an improvement in the circulation,
and recent ASCAT data show that the system has acquired a well-
defined center. Deep convection is organized in a large curved band,
however the center is located near the western edge of the band.
NOAA buoy 41046 located southeast of the center reported 25 to 30 kt
winds earlier this evening, and the scatterometer data support an
initial wind speed of 30 kt.

The depression is moving north-northwestward or 330/11 kt.
The depression should move north-northwestward to northward
around the western side of a deep-layer ridge over the central
Atlantic through Sunday night. It is expected to reach the
mid-latitude westerlies by late Monday and begin to accelerate
northeastward ahead of a short-wave trough that will be approaching
the northeastern United States.  The steering currents are well
established over the western Atlantic and the track guidance is in
good agreement on the forecast scenario. The NHC track forecast lies
near the various consensus aids.

The intensity forecast is more problematic.  The system is expected
to traverse warm water and remain in a low-shear environment during
the next day or so, but intrusions of dry mid-level air are likely
to limit strengthening.  The statistical guidance and the HWRF favor
more significant intensification than the global models, which
generally do not show much deepening.  In deference to the global
models, the NHC forecast is below the consensus, especially later in
the period.  The system is likely to become extratropical in 3 to 4
days, and the extratropical portion of the forecast is based on
guidance provided by the NOAA Ocean Prediction Center.


FORECAST POSITIONS AND MAX WINDS

INIT  13/0300Z 25.3N  70.3W   30 KT  35 MPH
 12H  13/1200Z 27.0N  71.2W   35 KT  40 MPH
 24H  14/0000Z 29.0N  71.9W   40 KT  45 MPH
 36H  14/1200Z 30.7N  72.0W   45 KT  50 MPH
 48H  15/0000Z 32.2N  71.4W   50 KT  60 MPH
 72H  16/0000Z 36.2N  66.9W   55 KT  65 MPH
 96H  17/0000Z 41.5N  54.5W   50 KT  60 MPH...POST-TROP/EXTRATROP
120H  18/0000Z 45.5N  39.0W   45 KT  50 MPH...POST-TROP/EXTRATROP

$$
Forecaster Brown

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