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Hurricane Larry Forecast Discussion Number 29
2021-09-07 22:54:19| National Hurricane Center (Atlantic)
Issued at 500 PM AST Tue Sep 07 2021 000 WTNT42 KNHC 072054 TCDAT2 Hurricane Larry Discussion Number 29 NWS National Hurricane Center Miami FL AL122021 500 PM AST Tue Sep 07 2021 After becoming rather ragged-looking in earlier satellite images, Larry's eye has become a little better defined recently, and the surrounding deep convection is more or less maintaining its strength. Observations from a NOAA Hurricane Hunter aircraft show that the central pressure has fallen slightly, to 965 mb. Peak flight-level winds from the aircraft were 110 kt so the advisory intensity is kept at 100 kt. This is also consistent with a Dvorak Current Intensity number from TAFB. Larry continues its northwestward motion at about 320/8 kt. The hurricane should move around the western side of a deep-layer subtropical anticyclone during the next 48-60 hours. After passing Bermuda, the system is likely to accelerate northeastward while moving into the mid-latitude westerlies ahead of a trough moving from the northeastern United States to Atlantic Canada, and move into the far north Atlantic by day 5. The official track forecast stays close to the previous NHC prediction, and remains in good agreement the various model consensus solutions. The hurricane continues to exhibit well-defined upper-level outflow, indicative of weak vertical shear. Over the next couple of days, Larry will be traversing waters of gradually decreasing oceanic heat content. This, combined with some dry mid-level air in the environment, should lead to a gradual decrease in intensity through 48-60 hours. Later in the forecast period, colder waters and strong shear should cause more rapid weakening. By day 4, the global models show Larry merging with a frontal zone. Therefore, the NHC forecast calls for extratropical transition by that time. The official intensity forecast is generally below the statistical-dynamical guidance and above the coupled dynamical hurricane models through 72 hours, but in good agreement with the model consensus aids. 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. The center of Larry is forecast to pass east of Bermuda on Thursday, but given Larry's large size, tropical storm conditions are possible there Thursday, along with a risk of heavy rainfall and coastal flooding. A Tropical Storm Watch 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 late Friday and Friday night as it transitions to a hurricane-force post-tropical cyclone. There is a risk of impacts from high winds, rainfall, and storm surge in portions of Newfoundland, and interests there should monitor the progress of Larry and updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 07/2100Z 25.1N 56.3W 100 KT 115 MPH 12H 08/0600Z 26.5N 57.4W 95 KT 110 MPH 24H 08/1800Z 28.3N 58.8W 95 KT 110 MPH 36H 09/0600Z 30.5N 60.5W 90 KT 105 MPH 48H 09/1800Z 33.3N 61.7W 90 KT 105 MPH 60H 10/0600Z 36.8N 61.2W 85 KT 100 MPH 72H 10/1800Z 41.7N 58.2W 80 KT 90 MPH 96H 11/1800Z 53.0N 48.0W 65 KT 75 MPH...POST-TROP/EXTRATROP 120H 12/1800Z 60.0N 38.0W 50 KT 60 MPH...POST-TROP/EXTRATROP $$ Forecaster Pasch
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