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Hurricane Larry Forecast Discussion Number 27
2021-09-07 10:48:57| National Hurricane Center (Atlantic)
Issued at 500 AM AST Tue Sep 07 2021 000 WTNT42 KNHC 070848 TCDAT2 Hurricane Larry Discussion Number 27 NWS National Hurricane Center Miami FL AL122021 500 AM AST Tue Sep 07 2021 Larry has maintained a very warm, pronounced eye with a diameter of around 45 to 50 n mi overnight. However, recent infrared satellite imagery and earlier microwave data show some weaknesses in the western eyewall of the hurricane, potentially signaling the entrainment of some drier air into its inner core. This could be the result of some moderate westerly shear impinging on the system. The initial intensity is lowered to 105 kt for this advisory, based on a 0520 UTC SATCON estimate of 103 kt and T5.5/102 kt current intensity Dvorak estimates from TAFB and SAB. An Air Force Reserve hurricane hunter reconnaissance flight is scheduled to investigate Larry later this morning, which should provide more insight into the hurricane's structure and intensity. Larry is moving toward the northwest at 315/9 kt, as the hurricane is being steered around a subtropical ridge over the central Atlantic. This general motion is expected to continue for the next 48 h or so. By Thursday, the hurricane is forecast to turn northward within the flow between the ridge and an approaching deep-layer trough that will be crossing the northeastern United States. As the trough moves over the western Atlantic, Larry should accelerate northeastward deeper into the mid-latitudes on Friday and Saturday, passing near or over portions of Atlantic Canada. The latest NHC track forecast lies near the HCCA and TVCA consensus aids, and no significant adjustments were made from the previous forecast. Larry is expected to pass east of Bermuda on Thursday as a large hurricane. Given the expansive size of its wind field, a Tropical Storm Watch could be required for the island later today. Although the warm sea-surface temperatures and diminishing vertical wind shear along Larry's forecast track appear favorable during the next couple of days, it may not be able to take advantage of these conditions due to its large size, as well as the potential for another eyewall replacement cycle. As previously noted, Larry's broad wind field and moderate forward speed could also result in some upwelling of cooler waters near its inner core. There remains a split in the intensity guidance, with the statistical-dynamical guidance notably higher than the coupled atmosphere-ocean models. The official NHC intensity forecast shows a gradual weakening of Larry during the next several days. Nonetheless, Larry will remain a forceful hurricane that continues to produce significant swell with far-reaching impacts through the week. After 72 h, Larry should begin its extratropical transition, and the official forecast shows Larry becoming a hurricane-force extratropical cyclone by 96 h. Key Messages: 1. Large swells generated by Larry will continue to affect the Lesser Antilles, portions of the Greater Antilles, and the Bahamas through midweek. 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 couple of days as a large and powerful hurricane, bringing a risk of strong winds, heavy rainfall, and coastal flooding to the island by Thursday. Tropical storm watches could be needed for the island later today, and interests in Bermuda should closely monitor the latest forecast updates. FORECAST POSITIONS AND MAX WINDS INIT 07/0900Z 23.8N 55.1W 105 KT 120 MPH 12H 07/1800Z 24.9N 56.0W 100 KT 115 MPH 24H 08/0600Z 26.5N 57.4W 95 KT 110 MPH 36H 08/1800Z 28.4N 59.1W 95 KT 110 MPH 48H 09/0600Z 30.6N 60.8W 95 KT 110 MPH 60H 09/1800Z 33.3N 61.8W 90 KT 105 MPH 72H 10/0600Z 37.1N 61.0W 85 KT 100 MPH 96H 11/0600Z 47.7N 52.4W 75 KT 85 MPH...POST-TROP/EXTRATROP 120H 12/0600Z 57.0N 43.0W 55 KT 65 MPH...POST-TROP/EXTRATROP $$ Forecaster Reinhart
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