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| #1152456 (Received by flhurricane at: 4:57 AM 12.Sep.2023) TCDAT3 Hurricane Lee Discussion Number 28 NWS National Hurricane Center Miami FL AL132023 500 AM AST Tue Sep 12 2023 Lee continues to exhibit a concentric eyewall structure in conventional satellite imagery. This has been confirmed by the Air Force Reserve Hurricane Hunters that investigated Lee early this morning, and they reported the outer eyewall had a large diameter of 80 n mi. The maximum 700-mb flight-level wind measured by the aircraft was 112 kt in the northeast quadrant, while the SFMR winds peaked around 90 kt. Although the satellite intensity estimates have fallen a bit this morning, the reduced flight-level winds support holding the initial intensity at 100 kt for this advisory. The minimum pressure of Lee remains 948 mb based on dropsonde data. Lee is still moving slowly west-northwestward (290/6 kt), with mid-level ridging established to the north and west of the hurricane. This steering pattern is expected to change during the next couple of days as a deep-layer trough moves across the eastern United States and produces a weakness in this ridge. As a result, Lee is forecast to turn northward and gradually accelerate during the middle and latter parts of this week. The track guidance envelope shows little cross-track spread during the first 3 days of the forecast period, and this portion of the NHC forecast is fairly similar to the previous one. While the core of the hurricane is forecast to pass west of Bermuda, the large wind field of the storm is likely to bring wind impacts to the island later this week, and tropical storm watches could be required later today. At days 4-5, there has been a slight westward shift in the guidance envelope, and accordingly the NHC track forecast was nudged in that direction toward the HCCA and TVCA aids. Based on Lee`s current satellite structure, as well as its slow forward motion and large wind field, little near-term strengthening is expected. Going forward, the large hurricane appears likely to begin upwelling cooler waters along its path, and in a few days it will encounter the cool wake left behind by recent western Atlantic hurricanes. Thus, gradual weakening is forecast through midweek. Later, the aforementioned trough is expected to produce stronger deep-layer shear over Lee, and the hurricane is forecast to move over significantly cooler waters as it passes north of the Gulf Stream. As a result, more significant weakening is shown at days 4-5, along with completion of its extratropical transition. Despite the weakening that is forecast, keep in mind that the expanding wind field of Lee will produce impacts well away from the storm center. KEY MESSAGES: 1. Dangerous surf and life-threatening rip currents will affect portions of the northern Leeward Islands, the Virgin Islands, Puerto Rico, Hispaniola, the Turks and Caicos Islands, the Bahamas, Bermuda, and most of the U.S East Coast through much of the week. 2. There is an increasing risk of strong winds, rainfall, and high surf impacts to Bermuda later this week, and tropical storm watches could be required for the island later today. 3. It remains too soon to know what level of additional impacts Lee might have along the Northeastern U.S. coast and Atlantic Canada late this week and this weekend. However, since wind and rainfall hazards will extend well away from the center as Lee grows in size, users should continue to monitor updates to Lee`s forecast during the next several days. FORECAST POSITIONS AND MAX WINDS INIT 12/0900Z 24.0N 65.4W 100 KT 115 MPH 12H 12/1800Z 24.4N 66.2W 100 KT 115 MPH 24H 13/0600Z 25.3N 67.0W 100 KT 115 MPH 36H 13/1800Z 26.6N 67.5W 95 KT 110 MPH 48H 14/0600Z 28.3N 67.9W 90 KT 105 MPH 60H 14/1800Z 30.4N 68.0W 85 KT 100 MPH 72H 15/0600Z 32.9N 67.6W 80 KT 90 MPH 96H 16/0600Z 39.0N 66.7W 70 KT 80 MPH 120H 17/0600Z 44.5N 66.0W 50 KT 60 MPH...POST-TROP/EXTRATROP $$ Forecaster Reinhart |
