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Tropical Depression Eta Forecast Discussion Number 18
2020-11-05 03:38:42| National Hurricane Center (Atlantic)
Issued at 900 PM CST Wed Nov 04 2020 000 WTNT44 KNHC 050238 TCDAT4 Tropical Depression Eta Discussion Number 18 NWS National Hurricane Center Miami FL AL292020 900 PM CST Wed Nov 04 2020 The rugged terrain of Central America is taking a toll on Eta. The low-level circulation is losing definition, and deep convection is well removed from the center. Eta was downgraded to a 30-kt tropical depression a few hours ago, and the initial intensity is held at that value for this advisory. The strongest winds are likely occurring offshore over the Gulf of Honduras, as noted in earlier ASCAT scatterometer surface wind data. Eta, or its remnant low, is forecast to move west-northwestward to northwestward during the next 12 to 24 hours, taking the cyclone across portions of Honduras during that time. In 24 to 36 hours, a turn to the north and then northeast is forecast as Eta feels some influence from a mid- to upper level trough moving over the northwestern Gulf of Mexico. As this trough slides southeastward across the Gulf, it should steer Eta northeastward at a faster forward speed toward Cuba, likely approaching that country late Saturday or Sunday. After that time, the models show Eta rotating around the north side of the trough (or cut-off low) in the vicinity of south Florida and the Florida Keys late this weekend and early next week. There is still a lot of spread in the model tracks at the 96- and 120-hour time periods, which is not surprising given the expected complex steering pattern. The NHC track forecast is adjusted a little to the east of the previous one to come into better agreement with the latest models, but confidence in the details of the extended track forecast is low. Continued weakening is expected while Eta remains inland over the rugged terrain of Central America, and the cyclone will likely degenerate into a remnant low or trough of low pressure on Thursday. Whatever is left of Eta, and the broad gyre that it is embedded within, will move offshore of Belize over the northwestern Caribbean Sea by Thursday night or Friday. The rate of intensification over the northwestern Caribbean Sea will likely be gradual because of the mixed environmental conditions. On one hand, Eta will be moving over warm water and in a region of upper-level diffluence, which should support convective growth and strengthening. Conversely, there will also be an increase in wind shear and the cyclone is likely to have a broad structure, which should prevent rapid intensification. The net result will likely be slow but steady strengthening, and Eta is forecast to be a strong tropical storm when it is near south Florida. The models are in fair agreement on Eta's future intensity, and this forecast is just a little higher than the previous one. Key Messages: 1. Through Monday morning, heavy rainfall from Eta will lead to catastrophic, life-threatening flash flooding and river flooding across portions of Central America, along with landslides in areas of higher terrain. Flash and river flooding is also possible across Jamaica, southeast Mexico, the Cayman Islands and western Cuba. 2. Eta is forecast to regain tropical storm strength over the northwestern Caribbean Sea late this week. Although the details of the future track and intensity of Eta are uncertain, there is an increasing risk of impacts from wind and rainfall in portions of Cuba, southern Florida and the Florida Keys this weekend and early next week. FORECAST POSITIONS AND MAX WINDS INIT 05/0300Z 14.2N 86.3W 30 KT 35 MPH...INLAND 12H 05/1200Z 15.0N 87.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 24H 06/0000Z 16.1N 87.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 06/1200Z 17.2N 86.8W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 07/0000Z 18.2N 85.5W 35 KT 40 MPH...TROPICAL CYCLONE 60H 07/1200Z 19.3N 83.7W 40 KT 45 MPH 72H 08/0000Z 20.4N 82.0W 45 KT 50 MPH 96H 09/0000Z 23.3N 79.9W 50 KT 60 MPH 120H 10/0000Z 24.7N 81.4W 55 KT 65 MPH $$ Forecaster Cangialosi
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