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| #1152800 (Received by flhurricane at: 12:06 PM 14.Sep.2023) TCDAT3 Hurricane Lee Discussion Number 37 NWS National Hurricane Center Miami FL AL132023 1100 AM AST Thu Sep 14 2023 The satellite presentation of Lee has degraded over the past day or so. An eye is no longer apparent but deep convection continues to wrap around the eastern and northern portions of the circulation. Deep convection has waned over the southwestern portions of the cyclone, likely due to an increase in southwesterly vertical wind shear and dry air entrainment. An Air Force Reserve reconnaissance aircraft that has been investigating Lee this morning has measured peak 700-mb flight-level winds of 96 kt, and the NOAA P-3 aircraft has found peak 8000 ft flight-level winds of 100 kt. However, peak SFMR winds from both aircraft have been around 70 kt. Using a blend of the flight-level and SFMR data, the initial wind speed has been lowered to 80 kt, but this could be a little generous. Lee is moving northward at a slightly faster forward speed of 12 kt. A faster northward to north-northeastward motion is expected during the next day or so around the western side of a mid-level ridge over the central Atlantic. A slight bend to the north-northwest toward the Gulf of Maine is likely late Friday or early Saturday as the southern extent of mid-latitude trough moves off the Mid-Atlantic coast. After that time, Lee is forecast to turn northeastward over Atlantic Canada. The dynamical model guidance is tightly clustered and only minor adjustments were made to the previous official forecast. The NHC track is close to a blend of the typically reliable GFS and ECMWF models. Southwesterly vertical wind shear is expected to increase over Lee during the next 24 to 36 hours, and this is likely to lead to gradual weakening during that time. Sea surface temperatures will decrease significantly just after 36 hours when Lee moves north of the Gulf Stream. The global model guidance suggests that Lee will begin extratropical transition Friday night and this is likely to be completed within 48 hours, if not a little sooner. The NHC intensity forecast is a blend of the HFIP corrected consensus and and the IVCN consensus model. It can`t be stressed enough, that regardless of Lee`s designation, it will remain a large and dangerous cyclone while it approaches eastern New England and Atlantic Canada. KEY MESSAGES: 1. Tropical storm conditions, heavy rainfall, and high surf will continue to impact Bermuda through Friday morning, 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. Tropical storm conditions are expected on Cape Cod, Martha`s Vineyard, and Nantucket where a Tropical Storm Warning is now in effect. Tropical storm conditions are possible elsewhere across New England and Atlantic Canada within the Tropical Storm Watch areas. 3. Heavy rainfall from Lee may produce localized urban and small stream flooding across eastern New England and into portions of New Brunswick and Nova Scotia from Friday night into Saturday night. 4. 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 14/1500Z 30.4N 68.3W 80 KT 90 MPH 12H 15/0000Z 32.2N 68.0W 75 KT 85 MPH 24H 15/1200Z 35.0N 67.2W 70 KT 80 MPH 36H 16/0000Z 38.2N 66.6W 70 KT 80 MPH 48H 16/1200Z 41.5N 66.5W 65 KT 75 MPH 60H 17/0000Z 44.0N 66.1W 55 KT 65 MPH...POST-TROP/EXTRATROP 72H 17/1200Z 47.0N 63.6W 45 KT 50 MPH...POST-TROP/EXTRATROP 96H 18/1200Z 52.6N 52.2W 35 KT 40 MPH...POST-TROP/EXTRATROP 120H 19/1200Z...DISSIPATED $$ Forecaster Brown |
