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Tropical Storm Elsa Forecast Discussion Number 23
2021-07-06 04:50:47| National Hurricane Center (Atlantic)
Issued at 1100 PM EDT Mon Jul 05 2021 000 WTNT45 KNHC 060250 TCDAT5 Tropical Storm Elsa Discussion Number 23 NWS National Hurricane Center Miami FL AL052021 1100 PM EDT Mon Jul 05 2021 Radar data from Cuba and Key West, Florida, along with surface observations, indicate that the center of Elsa is back over water, having emerged off the northern coast of of Cuba around 0200 UTC. Doppler velocity data from the NOAA WSR-88D at Key West indicate values of around 55 t at 10,000 ft, which supports equivalent surface winds of 49 kt. An Air Force reconnaissance aircraft flying just offshore the north coast of Cuba over deep water measured reliable SFMR surface winds of at least 50 kt. Based on these data, the intensity has been increased to 50 kt. The initial motion estimate is 330/10 kt. Just like over the past three days, no significant changes have been made to the previous track forecast or synoptic reasoning. Elsa is now moving north-northwestward around the southwestern periphery of a deep-layer ridge whose axis extends westward across the Atlantic to central Florida. The cyclone should gradually move around the ridge over the next 36 hours, turning northward on Tuesday and then north-northeastward Tuesday night and Wednesday morning. By late Wednesday, Elsa should accelerate northeastward ahead of a mid-latitude trough and frontal system, moving across the eastern United States to near Atlantic Canada. The new NHC track forecast is very similar to the previous advisory track, but was nudged slightly eastward due to the more eastward initial position, and lies a tad east of of the various tightly clustered track consensus models. Some additional strengthening is expected over the next 36 hours, with some of the SHIPS and global models showing Elsa possibly reaching 60 kt just before landfall along the northwestern Florida peninsula. This would typically require a Hurricane Watch for a small portion of northwest Florida. However, given that Elsa has been hugging a very tight mid-level moisture gradient -- a condition that is expected to continue until landfall occurs in about 36 hours -- the new official intensity forecast remains similar to the previous advisory and holds the peak intensity at 55 kt due to expected intermittent dry-air intrusions. Subsequent NHC forecasts can assess the new reconnaissance and model data that will be coming in later tonight, and determine if an increase in the intensity forecast and the issuance of a hurricane watch or warning is required. By 96 hours, the global models suggest that the cyclone will merge with a frontal zone, so the new intensity forecast continues to shows extratropical transition at that time. Key Messages: 1. Heavy rain will impact the Cayman Islands and Cuba tonight resulting in significant flooding and mudslides over Cuba. As Elsa approaches the Florida Keys, Florida Peninsula, and southeast Georgia through Wednesday, heavy rainfall may result in isolated flash, urban, and minor river flooding, with considerable flooding possible in southwest and western portions of Florida. Mid to late week, heavy rains across coastal South Carolina, North Carolina, and southeastern Virginia may result in isolated flash and urban flooding. 2. There is a danger of life-threatening storm surge along portions of the west coast of Florida Tuesday night and Wednesday, and a Storm Surge Warning has been issued for that area. 3. Tropical storm conditions are expected to continue across portions of central and western Cuba tonight, and spread northward across portions of the Florida Keys and the Florida west coast through Wednesday, where a Tropical Storm Warning is in effect. 4. There is a risk of tropical storm conditions along portions of the coasts of Georgia and the Carolinas Wednesday and Thursday. FORECAST POSITIONS AND MAX WINDS INIT 06/0300Z 23.5N 82.3W 50 KT 60 MPH 12H 06/1200Z 24.9N 82.9W 55 KT 65 MPH 24H 07/0000Z 26.9N 83.3W 55 KT 65 MPH 36H 07/1200Z 29.2N 83.1W 55 KT 65 MPH 48H 08/0000Z 31.6N 82.0W 30 KT 35 MPH...INLAND 60H 08/1200Z 34.0N 79.8W 30 KT 35 MPH...INLAND 72H 09/0000Z 36.9N 76.1W 30 KT 35 MPH...INLAND 96H 10/0000Z 43.3N 66.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 11/0000Z 50.5N 52.4W 40 KT 45 MPH...POST-TROP/EXTRATROP $$ Forecaster Stewart
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