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Hurricane Larry Forecast Discussion Number 39
2021-09-10 10:44:31| National Hurricane Center (Atlantic)
Issued at 500 AM AST Fri Sep 10 2021 000 WTNT42 KNHC 100844 TCDAT2 Hurricane Larry Discussion Number 39 NWS National Hurricane Center Miami FL AL122021 500 AM AST Fri Sep 10 2021 Larry's satellite presentation has remained largely unchanged overnight. Deep convection continues to persist over and to the northeast of the center, with a larger outer band around the eastern portion of the circulation. Subjective Dvorak intensity estimates from TAFB and SAB have lowered slightly, and the initial intensity has been adjusted downward to 75 kt. This lies between the lower subjective satellite estimates and the higher UW/CIMSS ADT and SATCON values. Larry is forecast to remain over warm waters and in low vertical wind shear conditions this morning, therefore little overall change in intensity is expected in the short term. The hurricane will cross the north wall of the Gulf Stream over much cooler SSTs this afternoon, but the increasingly fast forward speed of the system and baroclinic forcing from a mid-latitude trough approaching from the west is likely to help Larry maintain hurricane strength as is passes over southeastern Newfoundland tonight. Larry is forecast to become extratropical shortly thereafter, and some slight weakening should occur before the post-tropical cyclone is absorbed by a larger extratropical low near southern Greenland in a couple of days. The NHC intensity forecast is similar to the HCCA and IVCN consensus aids and also follows the trends of the latest global model guidance. Larry has turned north-northeastward or 015/23 kt. The track guidance is once again in excellent agreement that Larry should turn northeastward today and continue to accelerate ahead of the aforementioned trough. The center of Larry should pass over southeastern Newfoundland tonight, but users are reminded to not focus on the exact details of the track forecast as strong winds, heavy rainfall, and a dangerous storm surge will extend far from the center of the cyclone. The updated official forecast lies near the center of the track guidance envelope, but is slightly faster than the previous forecast during the first 36 hours. Key Messages: 1. Larry is forecast to move over portions of southeastern Newfoundland tonight as it undergoes transition to a hurricane-force post-tropical cyclone. Hurricane conditions, a dangerous storm surge, and heavy rainfall are expected in portions of southeastern Newfoundland where a Hurricane Warning in effect. 2. Large swells generated by Larry will continue to affect the Bahamas, Bermuda, and the east coast of the United States and Atlantic Canada through Saturday. 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 10/0900Z 37.7N 61.8W 75 KT 85 MPH 12H 10/1800Z 41.9N 59.2W 75 KT 85 MPH 24H 11/0600Z 48.6N 53.0W 70 KT 80 MPH 36H 11/1800Z 55.0N 46.8W 60 KT 70 MPH...POST-TROP/EXTRATROP 48H 12/0600Z 60.0N 42.0W 60 KT 70 MPH...POST-TROP/EXTRATROP 60H 12/1800Z...DISSIPATED $$ Forecaster Brown
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