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Tropical Storm ISAAC


Tropical Storm Isaac Discussion Number  30
NWS National Hurricane Center Miami FL       AL092018
1100 PM AST Fri Sep 14 2018

Isaac has rapidly lost organization since the last advisory. The
cyclone has been devoid of any deep convection for most of the
evening, with only a small burst recently forming well to the west
of where Isaac's low-level center is believed to be located. While
it is possible, if not likely, that the maximum winds have decreased
a little since this afternoon due to the lack of convection, the
initial intensity has been held at 35 kt based on earlier aircraft
data. A NOAA Hurricane Hunter aircraft is scheduled to investigate
Isaac again overnight and will provide a better estimate of the
strength and status of Isaac.

The global models continue to insist that Isaac could open into a
trough at any time, and based on the current state of the cyclone,
this could be imminent. The regional hurricane models, however, show
the development of one or more mesoscale lows embedded within a
larger cyclonic envelope that cause Isaac to persist for at least a
few more days in those models. While the global model solution still
seems more likely, I can't rule out that Isaac will persist a little
longer, so the NHC forecast still carries a 72 h forecast point.
Regardless of whether Isaac is a tropical storm or a tropical wave
over the next few days, heavy rains and occasional gusty winds are
still likely across much of the Greater Antilles through the next
couple of days.

It has been very difficult to try to pinpoint a low-level center of
Isaac over the past few hours, but based on microwave data it
appears to still be moving west at about 13 kt. The GFS and ECMWF
are in very good agreement and show Isaac, or its remnants, moving
steadily westward for the next several days. The regional models on
the other hand show a farther north motion, in part due to one or
more reformations of the center. The NHC forecast continues to favor
the global model solutions and is on the south side of the guidance
envelope, however if it becomes clear that Isaac will survive
longer, a northward adjustment may be required in later advisories.


INIT  15/0300Z 15.4N  69.5W   35 KT  40 MPH
 12H  15/1200Z 15.5N  71.3W   35 KT  40 MPH
 24H  16/0000Z 15.7N  73.3W   35 KT  40 MPH
 36H  16/1200Z 16.2N  75.3W   35 KT  40 MPH
 48H  17/0000Z 16.7N  77.4W   30 KT  35 MPH
 72H  18/0000Z 18.7N  81.4W   30 KT  35 MPH
 96H  19/0000Z...DISSIPATED

Forecaster Zelinsky