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| #1152494 (Received by flhurricane at: 10:57 AM 12.Sep.2023) TCDAT3 Hurricane Lee Discussion Number 29 NWS National Hurricane Center Miami FL AL132023 Issued by the NWS Weather Prediction Center College Park MD 1100 AM AST Tue Sep 12 2023 GOES-16 satellite and radar images from the NOAA Hurricane Hunter indicate that Lee is trying to consolidate into one large eyewall, but the eye remains obscured with fragments of the old eyewall structures. Peak 700-mb flight-level winds were about 110 kt, 0.5 km radar estimates were near 121 kt and surface SFMR estimates were about 90 kt, which could be under sampled with such a large radius of maximum winds. The initial wind speed is held at 100 kt as a compromise of the aircraft estimates. Lee is still moving slowly west-northwestward (300/5 kt), with mid-level ridging established to the north and east 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 on Thursday, prompting the Bermuda Weather Service to issue a Tropical Storm Watch. The latest NHC track was a compromise between the 6z GEFS and ECMWF ensembles in the days 4/5 time frame, as it is still too early to know if any leftward bend will occur as Lee approaches North America. No significant change in strength is expected in the near-term with Lee due to its current structure and large wind field. 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 forecast weakening, it is important to note 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 a Tropical Storm Watch has been issued for the island. 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 12/1500Z 24.3N 65.9W 100 KT 115 MPH 12H 13/0000Z 24.8N 66.6W 100 KT 115 MPH 24H 13/1200Z 25.9N 67.3W 100 KT 115 MPH 36H 14/0000Z 27.4N 67.8W 95 KT 110 MPH 48H 14/1200Z 29.4N 68.2W 90 KT 105 MPH 60H 15/0000Z 31.6N 68.0W 85 KT 100 MPH 72H 15/1200Z 34.3N 67.4W 80 KT 90 MPH 96H 16/1200Z 40.7N 66.6W 65 KT 75 MPH 120H 17/1200Z 45.3N 65.9W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Bann/Blake/Gallina |
