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| #1016249 (Received by flhurricane at: 11:02 AM 12.Sep.2020) TCDAT4 Tropical Depression Nineteen Discussion Number 4 NWS National Hurricane Center Miami FL AL192020 1100 AM EDT Sat Sep 12 2020 The tropical cyclone's cloud pattern has exhibited little change on satellite imagery over the past several hours, although recently the Miami radar shows better-defined banding features over the southern portion of the circulation. The current intensity estimate remains at 30 kt for now, which is consistent with surface observations over the extreme southern Florida peninsula. An Air Force Hurricane Hunter aircraft is scheduled to investigate the system in a few hours, which should provide a better estimate of the cyclone's intensity. Since the system will be traversing very warm waters and through a moist air mass with moderate vertical shear for the next few days, steady strengthening is anticipated. The cyclone will likely become a hurricane in 2-3 days, although an increase in vertical shear could slow the rate of intensification over the northern Gulf of Mexico. The official forecast intensity around 72 hours is very close to that shown by the simple and corrected model consensus predictions. The depression has been moving a little north of west, or about 280/8 kt. A west-northwestward or northwestward motion is expected for the next day or two, along the southwestern periphery of a mid-level high pressure system centered just east of the mid-Atlantic coast. This high is forecast to weaken within 2-3 days which should lead to a slowing of the forward motion by Monday. The forward speed is likely to remain slow through 96 hours, although a high that is predicted to build over the Florida peninsula in 4-5 days should push the system across the coastline before the end of the forecast period. The official track forecast is close to the corrected consensus track prediction, HCCA, which has been a reliable performer so far. Users are reminded to not to focus on the exact details of the track or intensity forecast as the average NHC track error at 96 h is around 150 miles and the average intensity error is around 15 mph. In addition, winds, storm surge, and rainfall hazards will extend far from the center. KEY MESSAGES: 1. The depression is forecast to strengthen to a hurricane early next week as it moves across the northeastern Gulf of Mexico, and there is an increasing risk of life-threatening storm surge and dangerous hurricane-force winds from southeastern Louisiana to the Alabama coast. Residents in these areas should closely monitor the progress of this system and updates to the forecast, as Storm Surge and Hurricane watches will likely be issued later today. 2. The depression is expected to produce flash flooding across portions of southern Florida and prolong existing minor river flooding across central Florida through Sunday. Flash, urban, and minor to isolated moderate river flooding is likely across portions of the central Gulf Coast Sunday through Tuesday. 3. Tropical storm conditions are possible by Sunday night in portions of the Florida Panhandle, where a Tropical Storm Watch is in effect. Wind gusts to tropical-storm force could occur over portions of the southern Florida Peninsula today. FORECAST POSITIONS AND MAX WINDS INIT 12/1500Z 25.6N 81.5W 30 KT 35 MPH 12H 13/0000Z 26.2N 83.0W 35 KT 40 MPH 24H 13/1200Z 27.1N 84.8W 40 KT 45 MPH 36H 14/0000Z 28.0N 86.4W 50 KT 60 MPH 48H 14/1200Z 28.7N 87.6W 60 KT 70 MPH 60H 15/0000Z 29.3N 88.5W 65 KT 75 MPH 72H 15/1200Z 29.8N 89.1W 70 KT 80 MPH 96H 16/1200Z 30.6N 89.9W 55 KT 65 MPH...INLAND 120H 17/1200Z 32.0N 89.5W 30 KT 35 MPH...INLAND $$ Forecaster Pasch |