ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM Hurricane Lee Discussion Number 40 NWS National Hurricane Center Miami FL AL132023 500 AM AST Fri Sep 15 2023 Lee appears to be in the very initial stages of extratropical transition. The cloud pattern is becoming increasingly asymmetric, and scatterometer data from last evening showed a band of strong winds developing along a boundary to the northwest of the center. Lee's initial intensity remains 75 kt based on continuity from last evening's reconnaissance and scatterometer data, but NOAA and Air Force Reserve Hurricane Hunter aircraft should be in the storm in a couple of hours to again sample the wind field. Lee has been wobbling a bit since yesterday afternoon, but the smoothed motion is northward (010 degrees) at a faster speed of 14 kt. Additional northward acceleration is expected during the next 24-36 hours as Lee moves along the western periphery of a mid-level ridge, and approaches a trough currently over New England. The track model guidance continues to be in very good agreement on bringing Lee's center very near the western end of Nova Scotia by Saturday afternoon, although the new NHC forecast is a little faster than the previous prediction. In 2-3 days, Lee is forecast to turn north-northeastward and northeastward across Atlantic Canada as it moves between the aforementioned ridge and a mid-level trough moving across Quebec. Although southerly shear is forecast to increase markedly through the day, baroclinic influences during Lee's extratropical transition are likely to keep the intensity relatively steady for the next 24 hours or so. During that time, the NHC intensity forecast is near the top end of the guidance suite, closest to the GFS and ECMWF solutions, and there is some possibility that a band of strong winds could develop near the front on the western side of the circulation over the Gulf of Maine. Extratropical transition is forecast to be complete by 36 hours (although it could be sooner), and Lee is likely to be weakening--but still near or just below hurricane force--as it is approaching Nova Scotia due to the continued shear and much colder ocean temperatures. Lee is expected to continue weakening while it moves across Atlantic Canada, and global model fields indicate that it is likely to be absorbed by another developing area of low pressure near Newfoundland and Labrador just after 72 hours. KEY MESSAGES: 1. Hurricane conditions are possible across portions of Down East Maine, southern New Brunswick, and western Nova Scotia on Saturday within the Hurricane Watch area. Tropical storm conditions and coastal flooding are expected to begin in southern New England within the Tropical Storm Warning area this afternoon, and spread northward along the coast of New England and over portions of Atlantic Canada through Saturday. These conditions are likely to lead to downed trees and potential power outages. 2. 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 tonight into Saturday night. 3. Tropical storm conditions and high surf will continue to impact Bermuda through this morning. FORECAST POSITIONS AND MAX WINDS INIT 15/0900Z 34.4N 67.5W 75 KT 85 MPH 12H 15/1800Z 36.8N 67.0W 75 KT 85 MPH 24H 16/0600Z 40.3N 66.7W 75 KT 85 MPH 36H 16/1800Z 43.4N 66.4W 60 KT 70 MPH...POST-TROP/EXTRATROP 48H 17/0600Z 46.3N 64.8W 50 KT 60 MPH...POST-TROP/INLAND 60H 17/1800Z 49.3N 61.1W 40 KT 45 MPH...POST-TROP/EXTRATROP 72H 18/0600Z 52.2N 55.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 96H 19/0600Z...DISSIPATED $$ Forecaster Berg NNNN