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Hurricane Larry Forecast Discussion Number 25
2021-09-06 22:45:42| National Hurricane Center (Atlantic)
Issued at 500 PM AST Mon Sep 06 2021 000 WTNT42 KNHC 062045 TCDAT2 Hurricane Larry Discussion Number 25 NWS National Hurricane Center Miami FL AL122021 500 PM AST Mon Sep 06 2021 NOAA aircraft have been investigating Larry for much of this afternoon, providing valuable information regarding the structure and intensity of the hurricane. Peak 700-mb flight-level winds of 110 kt with SFMR winds of 101 kt were measured in the northwestern eyewall a couple of hours ago, supporting an intensity of about 100 kt in that portion of the cyclone. During that pass through the hurricane, the aircraft tail Doppler radar measured winds of 121 kt at a height of 3 km in the northeastern eyewall, which equate to about 109 kt at the surface. Therefore, the initial intensity has been adjusted up to 110 kt for this advisory. A pair of dropsondes into the eye of Larry measured a minimum central pressure of 956 mb. Both the aircraft and earlier ASCAT data indicated that hurricane-force winds extend up to 60 n mi from the center, while tropical-storm-force winds extend up to 160 n mi from the center. Larry is maintaining its stable, annular structure with a very large, mostly clear eye. The environment surrounding Larry is not forecast to change much over the next couple of days, so only some minor fluctuations in intensity are anticipated during that time. By 72 hours, decreasing sea-surface temperatures and an increase in vertical wind shear should cause the hurricane to begin weakening. The only change to the NHC intensity forecast was a 5-kt increase through the first few days to accommodate the adjustment required to the initial intensity. By the end of the forecast period, Larry is expected to transition to a powerful extratropical cyclone. The latest NHC forecast remains on the high end of the guidance, closest to the Decay-SHIPS model. The hurricane continues to move northwest at 9 kt to the southwest of a subtropical ridge. The forecast track confidence has remained high over the past few days. Larry should continue its northwestward motion through Wednesday, and then reach the western periphery of the ridge in a few days, causing the cyclone to begin a turn to the north, then northeast late this week. This track would bring Larry on its closest approach to Bermuda on Thursday. After turning northeast, the cyclone should accelerate into the mid-latitude westerlies. The latest NHC forecast is little changed from the previous one, and remains near the middle of tightly clustered track guidance. Key Messages: 1. Large swells generated by Larry are affecting the Lesser Antilles and will spread to portions of the Greater Antilles, the Bahamas, and Bermuda today through Tuesday. Significant swells should reach the east coast of the United States and Atlantic Canada by midweek and continue affecting these shores through the end of the week. 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 guidance of lifeguards and local officials this week. 2. Larry is forecast to approach Bermuda during the next few days as a large and powerful hurricane, bringing a risk of strong winds, heavy rainfall, and coastal flooding to the island by the middle of this week. While it is too soon to determine the magnitude of these hazards and potential impacts on Bermuda, interests there should closely monitor the latest forecast updates during the next several days. FORECAST POSITIONS AND MAX WINDS INIT 06/2100Z 22.5N 53.9W 110 KT 125 MPH 12H 07/0600Z 23.4N 55.0W 110 KT 125 MPH 24H 07/1800Z 24.9N 56.3W 105 KT 120 MPH 36H 08/0600Z 26.5N 57.6W 105 KT 120 MPH 48H 08/1800Z 28.3N 59.1W 105 KT 120 MPH 60H 09/0600Z 30.4N 60.7W 105 KT 120 MPH 72H 09/1800Z 33.1N 61.7W 100 KT 115 MPH 96H 10/1800Z 41.2N 57.9W 90 KT 105 MPH 120H 11/1800Z 51.7N 46.4W 70 KT 80 MPH...POST-TROP/EXTRATROP $$ Forecaster Latto
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