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| #1151775 (Received by flhurricane at: 10:54 PM 07.Sep.2023) TCDAT3 Hurricane Lee Discussion Number 11 NWS National Hurricane Center Miami FL AL132023 1100 PM AST Thu Sep 07 2023 The Air Force Reserve Hurricane Hunters have found that Lee has skyrocketed to category 5 strength. The aircraft measured peak 700-mb flight-level winds of 148 kt and trustworthy SFMR winds slightly over 140 kt, and dropsonde data shows that the minimum pressure has plummeted to 928 mb. Based on these data, the initial intensity is set at 140 kt, and Lee`s maximum winds have increased by an incredible 70 kt over the past 24 hours. The hurricane has a clear 15 n mi-wide eye, with an infrared eye temperature as warm as 21 C surrounded by convective cloud tops as cold as -76 C. Additional strengthening appears likely, as Lee remains in a low-shear environment and over very warm waters near 30 degrees Celsius, and there are no signs of an imminent eyewall replacement. In fact, based on guidance from UW-CIMSS, the probability of a secondary eyewall formation during the next 24 hours is well below climatology. There is some chance that moderate deep-layer southwesterly shear could develop over the hurricane, but this could be offset by strong upper-level divergence and thus have little to no impact. To account for the recent rate of intensification, the NHC intensity forecast is slightly above the IVCN and HCCA consensus aids and shows a peak intensity of 155 kt in 12 hours. Amazingly, the 1800 UTC HAFS-A and -B runs show a peak intensity between 170-180 kt, but that`s getting into rarefied air. The NHC forecast will be adjusted accordingly if those solutions begin looking like a more distinct possibility. Only very gradual weakening is shown after 12-24 hours, and it is likely that Lee`s intensity will fluctuate for much of the forecast period. Lee is forecast to remain a dangerous category 4 or 5 hurricane for the next 5 days. For the next 5 days--through next Tuesday evening--Lee is expected to maintain a steady west-northwestward track, passing well to the north of the northern Leeward Islands, the Virgin Islands, and Puerto Rico. The hurricane is currently moving at about 12 kt, but it is expected to slow down considerably through early next week as the steering ridge to its north builds southwestward, effectively blocking Lee`s progress. The NHC track forecast remains of high confidence through day 5, and again, no significant changes were required from the previous forecast. Although there are some indications that Lee might begin a northward turn around the middle of next week, it is still way to soon to focus on specific model scenarios that far out into the future. KEY MESSAGES: 1. Lee has become a dangerous category 5 hurricane, and further strengthening is forecast overnight. Lee`s core is expected to move well north of the northern Leeward Islands, the Virgin Islands, and Puerto Rico this weekend and early next week. 2. Dangerous surf and life-threatening rip currents are likely in the northern Leeward Islands beginning Friday. These conditions will spread westward and northward, affecting Puerto Rico, Hispaniola, the Turks and Caicos, the Bahamas, and Bermuda through the weekend. 3. It is way too soon to know what level of impacts, if any, Lee might have along the U.S. East Coast, Atlantic Canada, or Bermuda late next week, particularly since the hurricane is expected to slow down considerably over the southwestern Atlantic. Regardless, dangerous surf and rip currents are expected along most of the U.S. East Coast beginning Sunday. Continue to monitor updates to Lee`s forecast during the next several days. FORECAST POSITIONS AND MAX WINDS INIT 08/0300Z 17.3N 52.4W 140 KT 160 MPH 12H 08/1200Z 18.1N 54.0W 155 KT 180 MPH 24H 09/0000Z 19.1N 56.1W 150 KT 175 MPH 36H 09/1200Z 20.1N 58.0W 145 KT 165 MPH 48H 10/0000Z 20.9N 59.6W 140 KT 160 MPH 60H 10/1200Z 21.5N 60.9W 135 KT 155 MPH 72H 11/0000Z 22.1N 62.2W 130 KT 150 MPH 96H 12/0000Z 23.2N 64.7W 125 KT 145 MPH 120H 13/0000Z 24.1N 66.6W 115 KT 130 MPH $$ Forecaster Berg |
