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Hurricane Larry Forecast Discussion Number 38
2021-09-10 04:44:46| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Thu Sep 09 2021 249 WTNT42 KNHC 100244 TCDAT2 Hurricane Larry Discussion Number 38 NWS National Hurricane Center Miami FL AL122021 1100 PM AST Thu Sep 09 2021 There is not much new to report in the satellite structure with Larry this evening. The hurricane consists of a small core region of cold convective cloud tops near and just north of the center with a much larger concentric band of more moderate convective activity encircling the smaller core. Radar from Bermuda also shows this structure well even as the hurricane pulls away from the island. The most recent subjective Dvorak satellite intensity estimates from SAB and TAFB were unchanged from this afternoon, and the initial intensity will remain at 80 kt for this advisory. Larry is now moving to the north and beginning to accelerate at 360/20 kt. The track guidance remains in good agreement that Larry should soon turn to the northeast and continue accelerating quickly ahead of a large mid-latitude trough. On the current track, Larry should pass near or over southeastern Newfoundland tomorrow night or Saturday morning, becoming post-tropical shortly after it passes by. The post-tropical cyclone Larry should continue to move rapidly to the northeast until it is absorbed by the aforementioned mid-latitude trough after 48 hours. The official track forecast again lies close to the various consensus model predictions, and is just a touch faster than the previous forecast. Larry has another 12 hours or so over warm Gulf Stream waters, and most of the guidance is in agreement that the hurricane should maintain its intensity in the short-term. However, more gradual weakening should begin thereafter once Larry moves over much cooler waters. Unfortunately, there is not much time for Larry to weaken before the hurricane impacts Newfoundland, and it also is possible the rapidly approaching mid-latitude trough will provide some baroclinic forcing that could expand the wind field of the hurricane further. The NHC intensity forecast remain close to the latest HCCA guidance which is quite similar to the previous forecast. After 24 hours, the latest forecast GFS and ECMWF simulated IR brightness temperature suggest that Larry's convection should quickly shear off after passing by Newfoundland, with the hurricane becoming a powerful post-tropical cyclone by 36 hours. Both of these models now also suggest the post-tropical cyclone will quickly be stretched and then absorbed as its captured by an even larger extratropical cyclone produced by the upstream trough after 48 hours. Key Messages: 1. Larry is forecast to move near or over portions of southeastern Newfoundland Friday night or early Saturday morning as it undergoes transition to a hurricane-force post-tropical cyclone. Hurricane conditions and dangerous storm surge are expected in portions of southeastern Newfoundland where a Hurricane Warning in effect. 2. Large swells generated by Larry will continue to affect the Leeward Islands, portions of the Greater Antilles, the Bahamas, Bermuda, and the east coast of the United States and Atlantic Canada through the end of the week. These swells will cause life-threatening surf and rip current conditions, and beachgoers and other interests along these coasts are urged to follow the guidance of lifeguards and local officials. FORECAST POSITIONS AND MAX WINDS INIT 10/0300Z 35.5N 62.3W 80 KT 90 MPH 12H 10/1200Z 39.0N 60.9W 80 KT 90 MPH 24H 11/0000Z 45.1N 56.1W 75 KT 85 MPH 36H 11/1200Z 52.0N 49.3W 65 KT 75 MPH...POST-TROP/EXTRATROP 48H 12/0000Z 58.1N 44.0W 60 KT 70 MPH...POST-TROP/EXTRATROP 60H 12/1200Z...DISSIPATED $$ Forecaster Papin
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