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| #1153008 (Received by flhurricane at: 10:54 PM 15.Sep.2023) TCDAT3 Hurricane Lee Discussion Number 43 NWS National Hurricane Center Miami FL AL132023 1100 PM AST Fri Sep 15 2023 Lee remains a very large and dangerous hurricane as it approaches the northeast United States and Atlantic Canada. The satellite depiction of Lee shows that the system continues to become more asymmetric, with most of the convection displaced to the north of the center. An earlier SSMI/S microwave pass shows thick banding on the northern and western side of the inner core, which is where the Air Force Hurricane Hunters found the strongest flight-level and surface winds. The initial intensity, based on aircraft reconnaissance data, will remain at 70 kt for this advisory. Air Force Hurricane Hunters will be investigating Lee again overnight. Lee continues to wobble as it approaches the northeastern United States and Atlantic Canada. The past few hours there has been a bit of a north-northeast jog. Whether this is more of a wobble or a longer-term motion is still to be determined. Global model guidance has been hinting that this type of motion would occur as it makes its approach towards Atlantic Canada, with a slight bend back to the north-northwest over the next 12-18 h. The track forecast was nudged to the right given the current motion, but it does show a north-northwestward motion in the short term. These slight adjustments on the final approach are minor given the very large wind field of Lee. Once Lee makes landfall, the system is expected to accelerate to the northeast as it moves in the flow on the east side of an approaching trough. Strong southerly vertical wind shear has displaced the convection to the northern side of the system. Dry air entrainment is also inhibiting convection on the southern and eastern side of the circulation. These hostile environmental conditions will persist as Lee moves over much cooler waters after it crosses the north wall of the Gulf Stream on Saturday. Lee is already showing signs of completing its extratropical transition, with displaced convection and an elongated center on a recent scatterometer pass, and thus this transition is now explicitly forecast to occur within the next 12 h. Gradual weakening is forecast throughout the period, the NHC intensity forecast is similar to the previous, closest to the GFS. KEY MESSAGES: 1. Hurricane conditions are possible across portions southern New Brunswick, and much of 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 very soon, 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 in portions of eastern Maine, New Brunswick and western Nova Scotia Saturday. FORECAST POSITIONS AND MAX WINDS INIT 16/0300Z 39.5N 65.8W 70 KT 80 MPH 12H 16/1200Z 41.7N 66.0W 65 KT 75 MPH...POST-TROP/EXTRATROP 24H 17/0000Z 44.5N 65.7W 55 KT 65 MPH...POST-TROP/EXTRATROP 36H 17/1200Z 47.3N 63.3W 45 KT 50 MPH...POST-TROP/EXTRATROP 48H 18/0000Z 50.6N 58.1W 40 KT 45 MPH...POST-TROP/EXTRATROP 60H 18/1200Z 53.0N 50.4W 40 KT 45 MPH...POST-TROP/EXTRATROP 72H 19/0000Z 54.3N 41.3W 35 KT 40 MPH...POST-TROP/EXTRATROP 96H 20/0000Z...DISSIPATED $$ Forecaster Kelly/Brown |
