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Potential Tropical Cyclone Nine Forecast Discussion Number 4
2019-09-13 16:55:46| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT Fri Sep 13 2019 000 WTNT44 KNHC 131455 TCDAT4 Potential Tropical Cyclone Nine Discussion Number 4 NWS National Hurricane Center Miami FL AL092019 1100 AM EDT Fri Sep 13 2019 Preliminary data from a reconnaissance plane indicate that the disturbance has not developed a well-defined center yet and continues to be characterized by an elongated SW to NE trough of low pressure. Satellite images however, suggest that the system could be consolidating a little bit farther to the east within the area of deep convection. The reconnaissance plane will also check this region soon. In this advisory, the initial position is a point near the middle of of the trough, but not quite as far east as the convective area. The initial intensity remains 25 kt. The disturbance is embedded within a moderate shear environment, but this parameter is not expected to be strong enough to halt development. The NHC forecast still calls for this system to become a tropical cyclone later today or Saturday. Global models develop the system and guidance suggests that the cyclone could even reach hurricane intensity by the end of the forecast period. By then, the system is expected to be over the Atlantic well southeast of the coast of the Carolinas. Due to a lack of a well-defined center, the initial motion is highly uncertain. It appears that there has been little motion during the past few hours. A weakness in the ridge over the western Atlantic is forecast to develop and this pattern should steer the system slowly toward the northwest and then northward. In about 3 days, an eastward moving mid-latitude trough will force the system to recurve away from the coast toward the Atlantic. The guidance has shifted a little to east this morning and consequently the NHC track forecast was adjusted in that direction. However, the official forecast is still on the western edge of the guidance envelope. If the disturbance develops a little more to the east, the track forecast will probably adjusted to the right later today. Key Messages: 1. The system is expected to become a tropical storm and bring tropical-storm-force winds and heavy rainfall to portions of the northwestern Bahamas later today and Saturday. Significant storm surge is not expected in the northwest Bahamas from this system. Residents there should follow any advice given by local officials. 2. The system could bring tropical-storm-force winds to portions of the Florida east coast over the weekend. Residents there should monitor the progress of this system and follow any advice given by local officials. 3. Heavy rainfall and scattered flash flooding is possible this weekend in coastal sections of eastern Florida, Georgia, and South Carolina. Depending on the track of the system, heavy rainfall could reach eastern North Carolina next week. 4. Note that forecast uncertainty for these disturbances is generally larger than for tropical cyclones, especially beyond 48-72 hours. FORECAST POSITIONS AND MAX WINDS INIT 13/1500Z 25.0N 74.5W 25 KT 30 MPH...POTENTIAL TROP CYCLONE 12H 14/0000Z 25.8N 76.5W 30 KT 35 MPH...TROPICAL CYCLONE 24H 14/1200Z 26.6N 78.0W 35 KT 40 MPH 36H 15/0000Z 28.0N 79.4W 40 KT 45 MPH 48H 15/1200Z 29.2N 80.0W 50 KT 60 MPH 72H 16/1200Z 31.0N 79.0W 60 KT 70 MPH 96H 17/1200Z 31.5N 75.0W 65 KT 75 MPH 120H 18/1200Z 32.0N 71.5W 70 KT 80 MPH $$ Forecaster Avila
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