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Tropical Storm Eta Forecast Discussion Number 40
2020-11-10 09:39:18| National Hurricane Center (Atlantic)
Issued at 300 AM CST Tue Nov 10 2020 000 WTNT44 KNHC 100839 TCDAT4 Tropical Storm Eta Discussion Number 40 NWS National Hurricane Center Miami FL AL292020 300 AM CST Tue Nov 10 2020 There hasn't been a lot of change to the cloud pattern of Eta overnight, with the center apparently located on the northwestern side of a small central dense overcast. Scatterometer data from earlier indicated 35-40 kt winds, and with the typical undersampling from that instrument, along with consensus 45-kt estimates from TAFB/SAB, so Eta's initial wind speed is kept at 45 kt. A NOAA Hurricane Hunter aircraft should be in the storm this morning. Eta is forecast to be in a low-to-moderate shear environment over warm SSTs for the next couple of days. Gradual strengthening is expected through early Thursday, with the main restrictive factor being nearby dry air. After that time, increasing shear and drier mid-level air are likely to cause Eta to weaken. The rate of this weakening is pretty uncertain, and a lot depends on how much Eta can re-intensify over the next couple of days. The new forecast is similar to the previous one, which is quite close to the consensus guidance. The storm has basically become stationary overnight. Eta should drift to north today due to steering flow changes with a nearby upper-level low losing influence while ridging east of Florida builds southward. A slow northward track is then anticipated for a couple of days over the east-central Gulf of Mexico in this flow pattern. Beyond that time, model guidance is in rather poor agreement, ranging from a stronger system moving faster to the northeast due to broad troughing over the south-central United States, to a weaker tropical cyclone getting caught under a narrow ridge over the Gulf of Mexico and turning west-southwestward. Since the new forecast expects Eta to be weakening, the NHC forecast will be west of the consensus and west of the previous track. I have little confidence in the long-range track forecast due to its seeming dependence on the intensity, and the wide spread in the guidance. Key Messages: 1. Heavy rainfall from Eta will continue across western Cuba and South Florida today and tonight. Additional flash and urban flooding, especially across previously inundated areas, will be possible in South Florida. Flash and urban flooding will also be possible for western Cuba. 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 10/0900Z 22.9N 85.5W 45 KT 50 MPH 12H 10/1800Z 23.1N 85.6W 50 KT 60 MPH 24H 11/0600Z 24.0N 85.6W 55 KT 65 MPH 36H 11/1800Z 25.0N 85.4W 60 KT 70 MPH 48H 12/0600Z 26.0N 85.3W 60 KT 70 MPH 60H 12/1800Z 26.8N 85.3W 50 KT 60 MPH 72H 13/0600Z 27.3N 85.4W 40 KT 45 MPH 96H 14/0600Z 28.8N 86.5W 35 KT 40 MPH 120H 15/0600Z 30.0N 87.0W 30 KT 35 MPH $$ Forecaster Blake
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