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| #1152543 (Received by flhurricane at: 5:09 PM 12.Sep.2023) TCDAT3 Hurricane Lee Discussion Number 30 NWS National Hurricane Center Miami FL AL132023 Issued by the NWS Weather Prediction Center College Park MD 500 PM AST Tue Sep 12 2023 GOES-East satellite and information from an Air Force Reserve Hurricane Hunter plane indicate a slight recent improvement in the inner-eye structure with a 5-mb pressure fall noted in the most recent pass. However, peak 700-mb flight-level winds were lower than 6 hr ago with SFMR estimates about the same. Given the mixed signals, we will maintain the initial wind speed at 100 kts for this advisory. The big change in the aircraft data was the sizable expansion of the whole wind field in the eastern semicircle of the hurricane, which was also shown by a late-arriving SAR pass this morning. Lee has turned northwestward (315/6 kt) as the mid-level ridging continues to its north and east. A digging eastern United States trough remains on track to weaken the ridge during the next few days. Lee is expected to turn more northward and accelerate by Thursday as a result of this pattern change. Even though the core of Lee is expected to be well west of Bermuda, Lee`s large wind field could arrive early Thursday on the island. After day 3, there is an increase in guidance spread as the hurricane interacts with an approaching frontal zone, which could cause a small leftward bend in the track. However, recent guidance has tightened somewhat, and the official forecast follows a middle-ground solution similar to the GEFS/ECMWF ensemble means, on the fast side of the consensus. The hurricane is expected to gradually weaken over the next few days while it moves over cooler waters into a higher-shear environment. Still, all of the guidance keep this system quite large and at hurricane-strength for the next few days. Once the circulation reaches the colder water north of the Gulf Stream, more significant weakening is expected at the day 4-5 period as it quickly transitions to an extratropical low. Little change was made to the previous forecast, which is also close to the consensus aids, and the forward speed north of the Gulf Stream will be important in the exact wind speed as Lee approaches the mainland. Note- The 34- and 50-kt wind speed probabilities beyond 36 hours in the text product and graphics are likely underestimating the risk of those winds occurring. This is because the forecast wind field of Lee is considerably larger than average compared to the wind field used to derive the wind speed probability product. 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 remains in effect 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 12/2100Z 24.7N 66.4W 100 KT 115 MPH 12H 13/0600Z 25.4N 67.0W 100 KT 115 MPH 24H 13/1800Z 26.7N 67.6W 95 KT 110 MPH 36H 14/0600Z 28.6N 68.1W 90 KT 105 MPH 48H 14/1800Z 30.7N 68.2W 85 KT 100 MPH 60H 15/0600Z 33.4N 67.6W 80 KT 90 MPH 72H 15/1800Z 36.4N 66.8W 75 KT 85 MPH 96H 16/1800Z 42.8N 66.5W 65 KT 75 MPH 120H 17/1800Z 47.1N 64.5W 40 KT 45 MPH...POST-TROP/EXTRATROP $$ Forecaster Gallina/Blake/Bann |
