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Tropical Storm Eta Forecast Discussion Number 39
2020-11-10 03:53:43| National Hurricane Center (Atlantic)
Issued at 900 PM CST Mon Nov 09 2020 000 WTNT44 KNHC 100253 TCDAT4 Tropical Storm Eta Discussion Number 39 NWS National Hurricane Center Miami FL AL292020 900 PM CST Mon Nov 09 2020 Eta's convective structure appears to be gradually becoming better organized this evening. The center is located near the northern edge of a band that wraps around the southeastern and southern portions of the circulation. Recent subjective Dvorak data T-numbers were 3.0, which still support an initial intensity of 45 kt. With Eta's structure gradually improving and a forecast for the cyclone to remain over SSTs of around 28C and in generally low vertical wind shear conditions, some re-strengthening is likely during the next 24-36 hours. Although the NHC intensity forecast shows Eta remaining just below hurricane strength, there is a possibility that the storm will briefly regain hurricane status over the southeastern Gulf of Mexico within the next day or so. By 48 hours, when the cyclone moves over the east-central Gulf of Mexico, increasing vertical wind shear and dry mid-level air are likely to result in weakening, and like the previous forecast, the new NHC forecast indicates that Eta could weaken to a tropical depression by the end of the period. Some of the global model guidance suggests that Eta could weaken even faster than indicated below after 72 hours. Recent satellite fixes indicate that Eta is moving southwestward but a little slower than before at around 8 kt. Eta should slow its forward progress overnight and then meander over the southeastern Gulf of Mexico on Tuesday as steering current collapse. In 36-48 hours, Eta should begin moving northward between a mid-level ridge over the western Atlantic and a broad trough over the central United States. After 72 hours, the spread in the guidance increases when Eta is expected to be weaker and be steered by the low-level flow. Most of the guidance shows a northwestward to northward motion at that time period but have varying forward speed. The NHC track shows a slow north-northwest motion late in the period to account for these differences. There is lower than normal confidence in the latter portion of the track forecast given the large spread in the guidance. Key Messages: 1. Heavy rainfall from Eta will continue across portions of Cuba, the Bahamas, and southern Florida and spread north into central Florida. Additional flash and urban flooding, especially across previously inundated areas, will be possible in South Florida tonight. Flash and urban flooding will also be possible for Cuba, the Bahamas and the remainder of southern Florida over the next several days. 2. Eta could approach the Florida Gulf Coast later this week as a tropical storm, and possibly bring impacts from rain, wind, and storm surge. Interests in this area should continue to monitor the progress of Eta and updates to the forecast this week. FORECAST POSITIONS AND MAX WINDS INIT 10/0300Z 23.2N 85.2W 45 KT 50 MPH 12H 10/1200Z 22.8N 85.5W 50 KT 60 MPH 24H 11/0000Z 23.4N 85.5W 60 KT 70 MPH 36H 11/1200Z 24.6N 85.3W 60 KT 70 MPH 48H 12/0000Z 25.8N 85.2W 55 KT 65 MPH 60H 12/1200Z 26.6N 85.2W 50 KT 60 MPH 72H 13/0000Z 27.0N 85.3W 45 KT 50 MPH 96H 14/0000Z 27.7N 85.6W 35 KT 40 MPH 120H 15/0000Z 29.0N 86.0W 30 KT 35 MPH $$ Forecaster Brown
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