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Tropical Storm Eta Forecast Discussion Number 30
2020-11-07 21:54:30| National Hurricane Center (Atlantic)
Issued at 400 PM EST Sat Nov 07 2020 000 WTNT44 KNHC 072054 TCDAT4 Tropical Storm Eta Discussion Number 30 NWS National Hurricane Center Miami FL AL292020 400 PM EST Sat Nov 07 2020 An earlier Air Force Reserve Hurricane Hunter aircraft found that Eta had strengthened to 50 kt with a central pressure of 994 mb. Since that time, the storm organization is unchanged in satellite imagery, while the central convection looks a little more ragged in radar data from Grand Cayman Island and Cuba. Eta is currently being affected by 25-35 kt of southwesterly vertical wind shear, and water vapor imagery shows upper-level dry air approaching the inner core from the west. The initial motion now 050/14. There is little change to the forecast philosophy through the first 96 h of the forecast. A mid- to upper-level trough over the Gulf of Mexico should steer Eta northeastward for the next 12 h or so, which would bring the center near or over the coast of central Cuba. Then from 12-96 h, the trough should cut off into a closed low near western Cuba, with Eta turning northward and eventually westward near the Florida Keys and south Florida as it merges with the low. The track guidance has shifted a little to the west over Cuba and a little to the south near Florida, possibly in response to data from the G-IV jet mission earlier today, and the new track forecast does likewise. The track guidance becomes quite divergent after 96 h, and the 96-120 h motion is now slower than the previous forecast as a result. The intensity forecast is tricky. Strong upper-level divergence caused by the trough is allowing the cyclone to strengthen. However, at some time in the next 24-48 h the shear and dry air entrainment should prevent any further strengthening. The intensity guidance shows a little intensification during the next 24-36 h with the bulk of the guidance peaking near 60 kt. After that time, the dry air should cause at least some weakening. The new intensity forecast is increased a bit from the previous forecast to show a 60-kt intensity at 24 and 36 h. This requires issuing a hurricane watch for the Florida Keys and portions of south Florida. Key Messages: 1. Heavy rainfall will continue across the Cayman Islands, portions of Cuba, and Jamaica, and will spread north into the Bahamas and southern Florida. This rain may result in significant, life-threatening flash flooding and river flooding in Cuba. Flash and urban flooding will also be possible for the Cayman Islands, Jamaica, the Bahamas and southern Florida, along with potential minor river flooding in central Florida. 2. Tropical storm conditions will continue for a few more hours in portions of the Cayman Islands, and are expected tonight and Sunday in portions of Cuba and the northwestern Bahamas, where Tropical Storm Warnings are in effect. 3. Damaging tropical-storm-force winds are expected Sunday night, with hurricane-force winds possible, in the Florida Keys and portions of the southern Florida peninsula, where a Tropical Storm Warning and Hurricane Watch are in effect. Elsewhere across portions of the east and west coasts of the Florida peninsula, the risk of tropical-storm-force winds will extend well away from Eta's center, and Tropical Storm Watches and Warnings are in effect. 4. A life-threatening storm surge is possible along portions of the southern coast of the Florida peninsula and the Florida Keys, where a Storm Surge Watch is in effect. Residents in the Storm Surge Watch area should follow any advice given by local officials. FORECAST POSITIONS AND MAX WINDS INIT 07/2100Z 20.4N 80.7W 50 KT 60 MPH 12H 08/0600Z 21.6N 79.4W 55 KT 65 MPH...INLAND 24H 08/1800Z 23.3N 79.0W 60 KT 70 MPH...OVER WATER 36H 09/0600Z 24.7N 79.9W 60 KT 70 MPH 48H 09/1800Z 25.2N 81.2W 55 KT 65 MPH 60H 10/0600Z 25.7N 82.8W 55 KT 65 MPH 72H 10/1800Z 26.1N 83.6W 50 KT 60 MPH 96H 11/1800Z 26.5N 84.0W 50 KT 60 MPH 120H 12/1800Z 27.0N 84.0W 45 KT 50 MPH $$ Forecaster Beven
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