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Tropical Depression Eta Forecast Discussion Number 24
2020-11-06 16:00:33| National Hurricane Center (Atlantic)
Issued at 900 AM CST Fri Nov 06 2020 417 WTNT44 KNHC 061500 TCDAT4 Tropical Depression Eta Discussion Number 24 NWS National Hurricane Center Miami FL AL292020 900 AM CST Fri Nov 06 2020 Satellite imagery indicates that Eta is producing organized convection in a large band over its northern and eastern quadrants, with the center located just off the coast of Belize near the western end of the band. These data, along with surface observations, also show that the circulation is elongated. The initial intensity remains 30 kt in agreement with a satellite intensity estimate from TAFB. An Air Force Reserve Hurricane Hunter aircraft is scheduled to investigate Eta this afternoon, and a NOAA flight is scheduled for this evening. The initial motion is a somewhat uncertain 025/6 kt. A developing mid- to upper-level trough over the Gulf of Mexico is expected to steer Eta northeastward for the next 48 h or so with an increase in forward speed. Between 48-72 h, the trough is forecast to become a closed low near south Florida and western Cuba, with Eta expected to turn northwestward around and into the low. After 72 h, the merged system is likely to move slowly west-northwestward. While the guidance is in good agreement on the synoptic evolution, there are a lot of differences in the track forecast details in terms of both the heading and the forward speed, with the GFS-based guidance tending to be to the east and north of the UKMET/ECMWF/Canadian. Overall, the consensus models have shifted a little to the east and north since the last advisory, and the new forecast track is also nudged in those directions. Eta will move over the warm waters of the northwestern Caribbean during the next 48 h or so, and the upper-level divergence is forecast to be quite strong. This should allow some strengthening, although this is likely to be slowed by 20-30 kt of southwesterly vertical wind shear. The intensity forecast for this part of the cyclone's life is similar to the previous forecast and lies a bit below the bulk of the intensity guidance. Between 48-72 h , Eta may take on at least some subtropical cyclone characteristics as it merges with the mid- to upper-level low. During this process, some of the guidance suggests the possibility that a tight inner wind core may develop. There is a chance that during this time that Eta could regain hurricane strength, although this would be an intensity above the current guidance. After 72 h, dry air entrainment is expected to cause the cyclone to weaken. 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. The new forecast track requires a Tropical Storm Warning for the Cayman Islands at this time, and a Tropical Storm Watch for portions of Cuba. Watches may be required for portions of south Florida and the Florida Keys later today or tonight. Key Messages: 1. Rainfall associated with Eta will continue to result in catastrophic, life-threatening flash flooding and river flooding across portions of Central America, along with landslides in areas of higher terrain. Significant, life-threatening flash flooding and river flooding is possible in the Cayman Islands and Cuba. Flash flooding and urban flooding is also possible for Jamaica and southeast Mexico. 2. This weekend Eta is expected to bring tropical storm conditions to portions of the Cayman Islands, where a Tropical Storm Warning is in effect. Tropical storm conditions possible in portions of western and central Cuba, where a Tropical Storm Watch is in effect. 3. There is an increasing risk of impacts from wind and flash and urban flooding due to heavy rainfall in portions of southern Florida, the Florida Keys and portions of the Bahamas this weekend and early next week. Tropical Storm or Hurricane Watches will likely be issued later today or tonight for a portion of this area. FORECAST POSITIONS AND MAX WINDS INIT 06/1500Z 17.8N 87.0W 30 KT 35 MPH 12H 07/0000Z 18.6N 85.7W 35 KT 40 MPH 24H 07/1200Z 19.7N 83.5W 40 KT 45 MPH 36H 08/0000Z 21.0N 81.4W 45 KT 50 MPH 48H 08/1200Z 22.7N 79.9W 50 KT 60 MPH...INLAND 60H 09/0000Z 24.1N 80.0W 55 KT 65 MPH...OVER WATER 72H 09/1200Z 25.0N 81.2W 55 KT 65 MPH 96H 10/1200Z 25.5N 84.0W 50 KT 60 MPH 120H 11/1200Z 26.5N 85.0W 50 KT 60 MPH $$ Forecaster Beven
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