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Tropical Storm Isaac Forecast Discussion Number 30
2018-09-15 04:39:03| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Fri Sep 14 2018 956 WTNT44 KNHC 150238 TCDAT4 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. FORECAST POSITIONS AND MAX WINDS 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
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