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Tropical Depression Eta Forecast Discussion Number 23
2020-11-06 09:36:58| National Hurricane Center (Atlantic)
Issued at 300 AM CST Fri Nov 06 2020 000 WTNT44 KNHC 060836 TCDAT4 Tropical Depression Eta Discussion Number 23 NWS National Hurricane Center Miami FL AL292020 300 AM CST Fri Nov 06 2020 Although satellite images and surface observations suggest that the circulation of Eta is elongated, deep convection has been increasing near and over the center during the past several hours. Unfortunately, the ASCAT scatterometer missed the region where Eta is located, so there has not been much additional data to analyze the structure and intensity of the cyclone. The initial wind speed is held at 30 kt based on a 2.0/30 kt Dvorak classification from TAFB. The NOAA and Air Force Hurricane Hunters are scheduled to investigate Eta later today, and that data will be helpful in analyzing the cyclone. The depression is moving northward at 7 kt. Eta is forecast to turn northeastward later today, and accelerate slightly in that direction through Saturday in response to a mid- to upper-level trough that is expected to slide southeastward across the Gulf of Mexico. This motion should take Eta to the west of the Cayman Islands on Saturday and then across Cuba Saturday night or Sunday. Around the time Eta is forecast to be near Cuba, the models show the storm slowing down and turning northwestward or westward as the trough cuts off, and Eta pivots around the north side of that cut off low. This change in the storm motion should bring Eta near or over the Florida Keys and south Florida late in the weekend and early next week. The details in the location and timing of where Eta and the mid- to upper-level low interact will be very important to the exact track of Eta for south Florida and the Florida Keys. The new track forecast is a touch to the north of the previous one when Eta is expected to be near Florida, to be in better agreement with the latest consensus aids. The cyclone is currently over warm water, in a moist environment, and will be moving into a region of upper-level diffluence as it tracks across the northwestern Caribbean Sea. These conditions should allow for thunderstorms to organize near the center and for the cyclone to gradually intensify during the next couple of days. However, rapid intensification seems unlikely given the broad structure of Eta. The models show an increase in shear and some dry air entraining into the circulation around the time it nears Cuba this weekend, which in combination with land interaction could limit additional strengthening by then. The intensity forecast for the 72-120 hour period is more complicated as it will depend on the trough interaction mentioned above. Most of the intensity models show Eta holding steady in strength after its passage over Cuba, and the NHC forecast does the same. The wind field of Eta is expected to increase in size during the next few days, and the cyclone will likely produce a large area of tropical-storm-force winds on its north side when it is near Cuba, the Florida Keys, and southern Florida. 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 later today. Although the details of the future track and intensity of Eta are still 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 and the northwestern Bahamas this weekend and early next week. FORECAST POSITIONS AND MAX WINDS INIT 06/0900Z 17.3N 87.4W 30 KT 35 MPH 12H 06/1800Z 18.0N 86.6W 35 KT 40 MPH 24H 07/0600Z 19.1N 84.5W 40 KT 45 MPH 36H 07/1800Z 20.2N 82.2W 45 KT 50 MPH 48H 08/0600Z 21.8N 80.3W 50 KT 60 MPH 60H 08/1800Z 23.5N 79.9W 55 KT 65 MPH 72H 09/0600Z 24.6N 80.7W 55 KT 65 MPH 96H 10/0600Z 25.1N 83.7W 55 KT 65 MPH 120H 11/0600Z 25.9N 85.0W 55 KT 65 MPH $$ Forecaster Cangialosi
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