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Hurricane Sam Forecast Discussion Number 26
2021-09-29 04:35:07| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Tue Sep 28 2021 000 WTNT43 KNHC 290234 TCDAT3 Hurricane Sam Discussion Number 26 NWS National Hurricane Center Miami FL AL182021 1100 PM AST Tue Sep 28 2021 Satellite images suggest that Sam has strengthened. The eyewall of the hurricane has become more intense, with a warmer eye noted during the past several hours since the last reconnaissance aircraft departed. The initial wind speed is nudged upward to 120 kt, a little above what the previous aircraft mission from this afternoon supported. Another Air Force Reserve Hurricane Hunter plane is scheduled to fly through Sam in a few hours for a better look at the intensity. Sam is forecast to move into an area with somewhat lower wind shear and higher ocean heat content by late Wednesday. In addition, the hurricane will likely be moving a little faster, which decreases the upwelling potential under the storm. These factors lead me to believe Sam isn't quite done intensifying, and could reach another peak sometime late Wednesday or Thursday. The one fly-in-the- ointment to this forecast is another eyewall replacement cycle potentially beginning, although recent microwave data doesn't give that impression. Thus, the new forecast is raised from the last one during the first couple of days, on the higher side of the guidance. A more consistent weakening trend is expected late week, due to cooler SSTs and increasing shear, and no significant changes were made to the official forecast at long range. The hurricane continues moving northwestward at about 8 kt. Models are locked into this track continuing for the next day or two at a faster pace around the southwestern portion of a strengthening Atlantic subtropical ridge. Thereafter, Sam should turn northward on Friday and northeastward this weekend, likely a fair distance east of Bermuda, due to a large mid-latitude trough moving off of the United States east coast. Model guidance remains in close agreement on almost all of the forecast, and the only significant change from the last advisory is an eastward adjustment on Day 5 due to guidance suggesting that Sam gets shunted more eastward by the trough, rather than captured by it. Key Messages: 1. Large swells generated by Sam are affecting the Leeward Islands and will spread to portions of the Virgin Islands, Puerto Rico, Hispaniola, the Bahamas, and Bermuda by Thursday or Friday. Significant swells will likely reach the east coast of the United States and Atlantic Canada by the weekend. These swells will likely cause life-threatening surf and rip current conditions, and beachgoers and other interests along these coasts are urged to follow the advice of lifeguards and local officials through the upcoming weekend. FORECAST POSITIONS AND MAX WINDS INIT 29/0300Z 18.4N 55.6W 120 KT 140 MPH 12H 29/1200Z 19.1N 56.7W 120 KT 140 MPH 24H 30/0000Z 20.2N 58.2W 125 KT 145 MPH 36H 30/1200Z 21.8N 59.9W 125 KT 145 MPH 48H 01/0000Z 23.9N 61.2W 120 KT 140 MPH 60H 01/1200Z 26.4N 61.9W 115 KT 130 MPH 72H 02/0000Z 29.1N 61.8W 110 KT 125 MPH 96H 03/0000Z 35.0N 58.0W 100 KT 115 MPH 120H 04/0000Z 40.0N 52.0W 85 KT 100 MPH $$ Forecaster Blake
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