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Tropical Depression Isaac Discussion Number  28
NWS National Hurricane Center Miami FL       AL092018
1100 AM AST Fri Sep 14 2018

Deep convection has been increasing near the center of Isaac, but
visible imagery indicates that the circulation has become
more elongated from northeast to southwest.  It is possible that
Isaac is in the process of losing a well-defined center, but we will
know more about the wind structure in a few hours since the NOAA
Hurricane Hunter aircraft should be in the area.  The initial wind
speed is held at 30 kt.

Vertical shear has decreased near Isaac, with some outflow in the
western semicircle noted and consolidation of the convection.
Still, this area of the eastern Caribbean isn't known as the
graveyard for nothing, and the system might just be too shallow and
disorganized to take advantage of the changing environment.  Almost
all of the dynamical models, save the UKMET, show the cyclone moving
westward to west-northwestward at a slower forward speed during the
next few days and degenerating into an open wave in the central
Caribbean Sea.  This solution is also supported by fewer members of
the GFS and ECMWF ensemble now maintaining a coherent system in the
long range.  Little change is made to the previous track and
intensity forecasts, and we will see what the aircraft finds this
afternoon and if the 1200 UTC model cycle maintains the dissipation
trend.

FORECAST POSITIONS AND MAX WINDS

INIT  14/1500Z 14.9N  67.3W   30 KT  35 MPH
 12H  15/0000Z 15.0N  69.0W   30 KT  35 MPH
 24H  15/1200Z 15.1N  71.3W   30 KT  35 MPH
 36H  16/0000Z 15.2N  73.3W   25 KT  30 MPH
 48H  16/1200Z 15.6N  75.3W   25 KT  30 MPH
 72H  17/1200Z 17.0N  79.5W   25 KT  30 MPH
 96H  18/1200Z...DISSIPATED

$$
Forecaster Blake

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