000
WTNT44 KNHC 172048
TCDAT4

Tropical Storm Harvey Discussion Number   2
NWS National Hurricane Center Miami FL       AL092017
500 PM AST Thu Aug 17 2017

An Air Force Reserve Hurricane Hunter aircraft found a well-defined
circulation in the low pressure area east of the Lesser Antilles,
with the center near a cluster of sheared, but strong, convection.
The aircraft data suggest that the maximum winds are near 35 kt
and that the central pressure is near 1004 mb.  Based on these
data, the disturbance is upgraded to Tropical Storm Harvey.

The initial motion is 270/16.  There is no change to the forecast
philosophy since the previous advisory.  A deep-layer ridge to the
north of the system should steer it quickly just north of due west
through the forecast period, with this motion expected to bring the
system through the Lesser Antilles and into the eastern Caribbean
Sea in 12-24 h, into the central Caribbean by 48-72 h, and to the
western Caribbean by 96-120 h.  One adjustment is that the 96-120 h
points have been nudged a little southward in response to a shift in
the guidance, and thus now lie closer to Central America than on
the previous forecast.  The forecast track again lies near the
center of the tightly clustered guidance envelope and the various
consensus models.

The system is in an area of moderate easterly vertical shear, and
the large-scale models suggest that light/moderate shear should
continue through at least 72 h.  The conflicting forecast scenarios
alluded to in the previous advisory remain, with the SHIPS and
LGEM models still showing steady intensification while the GFS and
ECMWF models still forecast degeneration to an easterly wave over
the central Caribbean.  The new intensity forecast again follows the
trend of the SHIPS/LGEM models, but it remains on the low side of
the guidance envelope out of respect for the GFS/ECMWF. The 96-120 h
intensities have been decreased a little due to the forecast track
showing more land interaction.


FORECAST POSITIONS AND MAX WINDS

INIT  17/2100Z 13.0N  55.8W   35 KT  40 MPH
 12H  18/0600Z 13.1N  58.3W   35 KT  40 MPH
 24H  18/1800Z 13.4N  61.6W   40 KT  45 MPH
 36H  19/0600Z 13.7N  65.1W   45 KT  50 MPH
 48H  19/1800Z 14.0N  68.8W   45 KT  50 MPH
 72H  20/1800Z 14.5N  76.5W   55 KT  65 MPH
 96H  21/1800Z 15.5N  83.5W   60 KT  70 MPH
120H  22/1800Z 17.0N  88.5W   55 KT  65 MPH...INLAND

$$
Forecaster Beven