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Hurricane Larry Forecast Discussion Number 40
2021-09-10 16:48:30| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Fri Sep 10 2021 000 WTNT42 KNHC 101448 TCDAT2 Hurricane Larry Discussion Number 40 NWS National Hurricane Center Miami FL AL122021 1100 AM AST Fri Sep 10 2021 Larry remains a well organized hurricane at a high latitude, and it is quickly approaching southeastern Newfoundland. Satellite images show a fairly tight inner core and large curved bands surrounding that feature. However, there are some notable dry slots between the core and bands that have developed during the past several hours. The latest Dvorak numbers have nudged downward, with the CI values ranging between 65 kt and 72 kt. Based on these estimates, and a very recent ASCAT pass that showed peak winds near 65 kt, the initial intensity is set at 70 kt for this advisory. The cyclone remains quite large, with hurricane-force winds and tropical-storm-force winds estimated to extend outward up to 80 and 210 n mi from the center, respectively. The hurricane is in the process of turning to the right, with the latest initial motion estimated to be a fairly quick 015/25 kt. An even faster north-northeast to northeast motion is expected during the next day or two as the hurricane moves in the fast flow between a mid- to upper-level trough over the northeastern U.S./eastern Canada and a mid-level ridge over the central Atlantic. This motion should take Larry across southeastern Newfoundland tonight. Larry is then expected to merge with a large extratropical low over the Labrador Sea on Sunday. The NHC track forecast is similar to the previous one and near the middle of the guidance envelope. Although Larry will be moving over cooler waters north of the Gulf Stream Current later today, the hurricane will likely hold its strength or weaken just a little before landfall. After landfall, the models show the inner core dissipating, and the combination of land interaction, cooler waters, and an increase in shear should cause weakening and lead to extratropical transition by early Saturday. The NHC intensity forecast is close to the GFS model, which often performs well for hurricanes that transition to extratropical cyclones. 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 night. 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 10/1500Z 40.0N 60.5W 70 KT 80 MPH 12H 11/0000Z 45.1N 56.4W 70 KT 80 MPH 24H 11/1200Z 52.0N 49.4W 60 KT 70 MPH...POST-TROP/EXTRATROP 36H 12/0000Z 57.5N 44.0W 60 KT 70 MPH...POST-TROP/EXTRATROP 48H 12/1200Z 61.1N 38.7W 55 KT 65 MPH...POST-TROP/EXTRATROP 60H 13/0000Z...DISSIPATED $$ Forecaster Cangialosi
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