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| #1152780 (Received by flhurricane at: 4:57 AM 14.Sep.2023) TCDAT3 Hurricane Lee Discussion Number 36 NWS National Hurricane Center Miami FL AL132023 500 AM AST Thu Sep 14 2023 Lee`s satellite presentation has been a little deceiving early this morning, as earlier reconnaissance flight-level and dropsonde surface wind data indicated that the hurricane`s center was located about 15-20 n mi to the west of the satellite eye feature. On the last couple of passes of the Air Force Reserve C-130 through the center, the highest 700-mb wind measured was 95 kt, and peak SFMR readings from both the Air Force and NOAA were 70-75 kt. Accounting for some undersampling, Lee`s initial intensity is reduced slightly to 85 kt. The initial motion remains 350/8 kt. A faster northward motion, with some wobbles, is expected during the next 2-3 days as Lee moves between a mid-tropospheric high over the west-central Atlantic and a deep-layer trough over the eastern United States. As noted in earlier forecasts, a slight bend to the west toward the Gulf of Maine is likely in 48-60 hours when Lee interacts with the tail end of the trough over the Mid-Atlantic states. A turn toward the north-northeast and then northeast is forecast on days 3 and 4, bringing Lee`s center across Atlantic Canada. The NHC track forecast is nearly on top of the previous forecast, largely due to consistent and tightly clustered model guidance. The latest shear analyses suggest that moderate southwesterly shear has begun to affect Lee, and this is confirmed by the offset of the aircraft fixes relative to the satellite eye feature. The shear is forecast to increase further in 24-36 hours, which will cause Lee to ingest drier and more stable air into its circulation. In addition, sea surface temperatures along Lee`s future path drop off significantly after 36 hours. Therefore, continued gradual weakening is forecast, and the NHC intensity forecast is at or slightly above the intensity consensus aids for much of the forecast period. Extratropical transition is likely to begin on Friday as Lee interacts with a frontal boundary moving off the east coast of the United States, and a good chunk of the guidance suggests the transition could be complete by 60 hours. In order to maintain continuity with the previous forecast, Lee is now shown to be a fully post-tropical cyclone by 72 hours. Regardless of its designation, Lee will remain a large and dangerous cyclone while it approaches eastern New England and Atlantic Canada into the weekend. KEY MESSAGES: 1. Tropical storm conditions, heavy rainfall, and high surf are beginning to impact Bermuda, and a Tropical Storm Warning is in effect for the island. 2. Hurricane conditions and coastal flooding are possible in portions of eastern Maine, southern New Brunswick, and western Nova Scotia on Saturday, and a Hurricane Watch is in effect for that area. Heavy rainfall in these areas may produce localized urban and small stream flooding from Friday night into Saturday night. Tropical storm conditions are possible elsewhere across New England and Atlantic Canada within the Tropical Storm Watch areas. 3. There is the potential for life-threatening storm surge flooding in portions of southeastern Massachusetts, including Cape Cod and Nantucket, late Friday and Saturday, where a Storm Surge Watch is in effect. FORECAST POSITIONS AND MAX WINDS INIT 14/0900Z 29.1N 68.1W 85 KT 100 MPH 12H 14/1800Z 30.7N 68.2W 80 KT 90 MPH 24H 15/0600Z 33.3N 67.7W 80 KT 90 MPH 36H 15/1800Z 36.3N 66.9W 75 KT 85 MPH 48H 16/0600Z 39.5N 66.6W 70 KT 80 MPH 60H 16/1800Z 42.5N 66.7W 60 KT 70 MPH 72H 17/0600Z 45.2N 65.4W 50 KT 60 MPH...POST-TROP/EXTRATROP 96H 18/0600Z 50.2N 58.1W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 19/0600Z 54.6N 45.8W 40 KT 45 MPH...POST-TROP/EXTRATROP $$ Forecaster Berg |
