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Tropical Depression Eta Forecast Discussion Number 20
2020-11-05 15:50:54| National Hurricane Center (Atlantic)
Issued at 900 AM CST Thu Nov 05 2020 000 WTNT44 KNHC 051450 TCDAT4 Tropical Depression Eta Discussion Number 20 NWS National Hurricane Center Miami FL AL292020 900 AM CST Thu Nov 05 2020 Eta remains disorganized this morning, as visible imagery suggests that the circulation has become elongated and that multiple vorticity centers may be present inside the larger cyclonic envelope. The center position for this advisory, which is over northwestern Honduras, is closer to convection in the northwestern semicircle than was the case 6 h ago, so the cyclone is being maintained as a tropical depression at this time. The initial motion is a somewhat uncertain 305/8 kt. Eta or its remnants should move generally northwestward today, then turn northward tonight. From 24-72 h, the system should move northeastward in response to a developing mid- to upper-level trough over the central and eastern Gulf of Mexico. From 72-120 h, the trough is forecast to become a closed mid- to upper-level low in the vicinity of western Cuba, with the center of Eta likely to turn west-northwestward on the north side of the low. While the global models are in good agreement with this synoptic evolution, there is a significant spread in the forecast tracks between the fastest and farthest east GFS and the slowest and farthest west UKMET. The new forecast track lies between these extremes in best overall agreement with the ECMWF and Canadian models, and it calls for the system to be near western Cuba and the Cayman Islands in 60-72 h, and then be over the southeastern Gulf of Mexico by the end of the forecast period. Little change in strength is expected before the center moves back over the Caribbean, but there is still a chance that Eta could degenerate to a remnant low pressure area later today if the convection does not persist. Intensification is expected over the warm waters of the Caribbean Sea from 24-72 h, although this may be slowed by southwesterly shear caused by the aforementioned trough. As the trough cuts off near or over Eta between 72-120 h, the global models suggest that the system could strengthen while acquiring at least some subtropical or hybrid characteristics due to upper-level cold air entrainment. The new intensity forecast is little changed from the previous forecast, and in the latter part of the forecast period it lies near the intensity consensus. It should be noted that while Eta regaining hurricane strength cannot be ruled out, there is little support for that in the current guidance. 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 the Cayman Islands, Cuba, southern Florida and the Florida Keys this weekend and early next week. FORECAST POSITIONS AND MAX WINDS INIT 05/1500Z 15.1N 87.8W 25 KT 30 MPH...INLAND 12H 06/0000Z 15.7N 88.0W 25 KT 30 MPH...INLAND 24H 06/1200Z 16.8N 87.6W 25 KT 30 MPH...OVER WATER 36H 07/0000Z 17.8N 86.2W 30 KT 35 MPH 48H 07/1200Z 19.0N 84.5W 35 KT 40 MPH 60H 08/0000Z 20.1N 83.0W 45 KT 50 MPH 72H 08/1200Z 21.3N 81.2W 50 KT 60 MPH 96H 09/1200Z 23.0N 80.0W 50 KT 60 MPH 120H 10/1200Z 24.0N 83.0W 55 KT 65 MPH $$ Forecaster Beven
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