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Hurricane Larry Forecast Discussion Number 35
2021-09-09 10:46:32| National Hurricane Center (Atlantic)
Issued at 500 AM AST Thu Sep 09 2021 652 WTNT42 KNHC 090846 TCDAT2 Hurricane Larry Discussion Number 35 NWS National Hurricane Center Miami FL AL122021 500 AM AST Thu Sep 09 2021 This morning's conventional satellite presentation appears to indicate a more banding eye feature rather than a previously noted irregular-type eye. A timely Advanced Technology Microwave Sounder (ATMS) image and an AMSR2 lower frequency pass, however, clearly shows the majority of the eyewall intact. The primary curved band wrapping around the west semicircle consists of -78 Celsius cloud tops. The western portion of the eyewall is now discernible on the Bermuda Weather Service Radar. The initial intensity is held at possibly generous 85 kt for this advisory and is based on a compromise of the subjective and objective satellite intensity estimates. A 53rd Air Force Reserve Unit reconnaissance mission is scheduled for this morning and will provide new information on Larry's intensity. The 0000 UTC GFS global model sounding revealed 15 to 20 kt of southwesterly effective shear impinging on the western half of the cyclone while the UW-CIMSS shear analysis showed 20-25 kt of bulk shear in the same area. This, along with a significantly higher statically stable surrounding environment (about 55 percent RH), has disrupted the inner core and more than likely created a SW to NW tilt with height. Larry is expected to change little in strength during the next 12 to 24 hours, then gradually weaken as the cyclone traverses sharply decreasing cooler water north of the gulf stream while the southwesterly shear increases significantly. The dynamic forcing, however, associated with a mid-latitude major shortwave trough near Atlantic Canada should aid in maintaining Larry as a hurricane while it passes near or over Newfoundland. Afterwards, Larry is expected to transition into a large extratropical cyclone, as indicated by the FSU Cyclone Phase Diagram. By early next week, Larry is expected to be absorbed by a larger extratropical low. The initial motion is estimated to be north-northwestward, or 330/14 kt. The track philosophy remains unchanged. Larry is expected to move around the western periphery of a subtropical high pressure system anchored over the central Atlantic. The hurricane should make its closest approach to the east of Bermuda later today while slowly turning north-northwestward and northward. Through the remaining portion of the forecast, Larry should accelerate generally northeastward in response to the aforementioned mid-latitude trough and move near or over southeastern Newfoundland Friday night. The NHC forecast has been nudged a bit to the left of the previous advisory and is close to the various multi-model consensus aids. The wind radii were decreased slightly in all quadrants based on earlier METOP A and B scatterometer passes. Key Messages: 1. 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 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. The center of Larry is forecast to pass east of Bermuda later today, Tropical storm conditions are expected today, along with a risk of coastal flooding. A Tropical Storm Warning is in effect for Bermuda, and interests there should closely monitor the latest forecast updates. 3. Larry is forecast to move near or over portions of southeastern Newfoundland Friday night, early Saturday morning as it undergoes transition to a hurricane-force post-tropical cyclone. Hurricane and Tropical Storm Watches are in effect for southeastern Newfoundland. There is an increasing risk of impacts from high winds, rainfall, and storm surge in portions of Newfoundland, and interests there should monitor updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 09/0900Z 30.9N 61.1W 85 KT 100 MPH 12H 09/1800Z 32.9N 62.1W 85 KT 100 MPH 24H 10/0600Z 36.7N 62.0W 85 KT 100 MPH 36H 10/1800Z 41.8N 59.0W 80 KT 90 MPH 48H 11/0600Z 47.9N 52.5W 70 KT 80 MPH 60H 11/1800Z 54.1N 45.9W 60 KT 70 MPH...POST-TROP/EXTRATROP 72H 12/0600Z 59.2N 41.2W 60 KT 70 MPH...POST-TROP/EXTRATROP 96H 13/0600Z...ABSORBED $$ Forecaster Roberts
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