<span-size:10.5pt;font-family:"Courier New";color:black">142
<span-size:10.5pt;font-family:"Courier New";color:black">WTNT44 KNHC 130859
<span-size:10.5pt;font-family:"Courier New";color:black">TCDAT4
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<span-size:10.5pt;font-family:"Courier New";color:black">Tropical Storm Isaac Discussion Number 23
<span-size:10.5pt;font-family:"Courier New";color:black">NWS National Hurricane Center Miami FL AL092018
<span-size:10.5pt;font-family:"Courier New";color:black">500 AM AST Thu Sep 13 2018
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<span-size:10.5pt;font-family:"Courier New";color:black">Data from a NOAA P-3 Hurricane Hunter aircraft that departed the
<span-size:10.5pt;font-family:"Courier New";color:black">storm shortly before 0600 UTC indicated that the tropical storm has
<span-size:10.5pt;font-family:"Courier New";color:black">weakened a little more. Maximum flight-level winds were around 51
<span-size:10.5pt;font-family:"Courier New";color:black">kt, while maximum SFMR winds were only 41 kt. Both of these
<span-size:10.5pt;font-family:"Courier New";color:black">support an initial intensity of 40 kt. Wind measurements from the
<span-size:10.5pt;font-family:"Courier New";color:black">plane also suggested that Isaac is close to opening up into a
<span-size:10.5pt;font-family:"Courier New";color:black">tropical wave and its circulation is likely barely closed at the
<span-size:10.5pt;font-family:"Courier New";color:black">surface. Another P-3 mission is scheduled for this morning.
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<span-size:10.5pt;font-family:"Courier New";color:black">Isaac is nearly completely devoid of deep convection at the moment,
<span-size:10.5pt;font-family:"Courier New";color:black">and is not trackable in radar data from Guadeloupe and Martinique.
<span-size:10.5pt;font-family:"Courier New";color:black">Given the lack of deep convection to sustain the cyclone, continued
<span-size:10.5pt;font-family:"Courier New";color:black">gradual weakening is expected. However, given the extent of
<span-size:10.5pt;font-family:"Courier New";color:black">40 mph winds observed by the NOAA plane, Isaac is still likely to
<span-size:10.5pt;font-family:"Courier New";color:black">bring gusty conditions to many of the Leeward Islands through
<span-size:10.5pt;font-family:"Courier New";color:black">this afternoon. The dynamical guidance is now in fairly good
<span-size:10.5pt;font-family:"Courier New";color:black">agreement on the intensity of Isaac for the next few days, and
<span-size:10.5pt;font-family:"Courier New";color:black">nearly all of the models depict Isaac opening into a trough between
<span-size:10.5pt;font-family:"Courier New";color:black">48 and 96 h. The NHC forecast conservatively maintains Isaac
<span-size:10.5pt;font-family:"Courier New";color:black">through day 4 in an attempt to maintain some continuity, but it
<span-size:10.5pt;font-family:"Courier New";color:black">is very possible that Isaac will open into a trough sooner than
<span-size:10.5pt;font-family:"Courier New";color:black">indicated. Some of the dynamical models suggest that regeneration
<span-size:10.5pt;font-family:"Courier New";color:black">could occur in the western Caribbean, however the predictability of
<span-size:10.5pt;font-family:"Courier New";color:black">such an event is too low to explicitly show in the forecast at this
<span-size:10.5pt;font-family:"Courier New";color:black">point.
<span-size:10.5pt;font-family:"Courier New";color:black">
<span-size:10.5pt;font-family:"Courier New";color:black">Isaac is still moving quickly westward, with an initial motion of
<span-size:10.5pt;font-family:"Courier New";color:black">275/15 kt. Confidence in the track forecast remains high, and the
<span-size:10.5pt;font-family:"Courier New";color:black">track guidance is tightly clustered through the forecast period.
<span-size:10.5pt;font-family:"Courier New";color:black">Very little change was made to the track forecast, which continues
<span-size:10.5pt;font-family:"Courier New";color:black">to closely follow the HCCA model. As long as Isaac remains a
<span-size:10.5pt;font-family:"Courier New";color:black">shallow cyclone, it should continue to be steered westward by the
<span-size:10.5pt;font-family:"Courier New";color:black">low-level tradewind flow, even if, or when, it opens up into a
<span-size:10.5pt;font-family:"Courier New";color:black">trough.
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<span-size:10.5pt;font-family:"Courier New";color:black">Key Messages:
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<span-size:10.5pt;font-family:"Courier New";color:black">1. Isaac is expected to produce tropical-storm-force winds across
<span-size:10.5pt;font-family:"Courier New";color:black">portions of the Lesser Antilles this morning and afternoon, and
<span-size:10.5pt;font-family:"Courier New";color:black">tropical storm warnings are in effect for Martinique, Dominica, and
<span-size:10.5pt;font-family:"Courier New";color:black">Guadeloupe.
<span-size:10.5pt;font-family:"Courier New";color:black">
<span-size:10.5pt;font-family:"Courier New";color:black">2. Tropical storm watches are in effect for Montserrat, St. Kitts
<span-size:10.5pt;font-family:"Courier New";color:black">and Nevis, Antigua, Barbuda, Saba and St. Eustatius, St. Maarten,
<span-size:10.5pt;font-family:"Courier New";color:black">and St. Martin. Tropical storm conditions are possible on these
<span-size:10.5pt;font-family:"Courier New";color:black">islands today and interests on those islands should follow any
<span-size:10.5pt;font-family:"Courier New";color:black">advice given by their local officials.
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<span-size:10.5pt;font-family:"Courier New";color:black">FORECAST POSITIONS AND MAX WINDS
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<span-size:10.5pt;font-family:"Courier New";color:black">INIT 13/0900Z 15.4N 59.7W 40 KT 45 MPH
<span-size:10.5pt;font-family:"Courier New";color:black">12H 13/1800Z 15.5N 61.8W 35 KT 40 MPH
<span-size:10.5pt;font-family:"Courier New";color:black">24H 14/0600Z 15.5N 64.8W 35 KT 40 MPH
<span-size:10.5pt;font-family:"Courier New";color:black">36H 14/1800Z 15.5N 67.8W 35 KT 40 MPH
<span-size:10.5pt;font-family:"Courier New";color:black">48H 15/0600Z 15.4N 70.4W 35 KT 40 MPH
<span-size:10.5pt;font-family:"Courier New";color:black">72H 16/0600Z 15.6N 74.8W 35 KT 40 MPH
<span-size:10.5pt;font-family:"Courier New";color:black">96H 17/0600Z 16.9N 78.5W 30 KT 35 MPH
<span-size:10.5pt;font-family:"Courier New";color:black">120H 18/0600Z...DISSIPATED
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<span-size:10.5pt;font-family:"Courier New";color:black">$$
<span-size:10.5pt;font-family:"Courier New";color:black">Forecaster Zelinsky
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