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| #1194088 (Received by flhurricane at: 11:00 AM 16.Aug.2024) TCDAT5 Hurricane Ernesto Discussion Number 20 NWS National Hurricane Center Miami FL AL052024 1100 AM AST Fri Aug 16 2024 Ernesto appears to be feeling the effects of vertical wind shear this morning. The structure on satellite has become more asymmetric with the coldest cloud tops shifted to the east of the center fixes being made by an ongoing Air Force Hurricane Hunter mission, which also found a 50-mile-wide eye open to the southwest. Despite the degraded satellite appearance, the aircraft still found 700-mb flight-level winds up to 98 kt, with peak SFMR-derived winds of 76 kt in the southeast quadrant of Ernesto. A blend of these data still supports an intensity of 85 kt this advisory, though this could be generous. The hurricane remains quite large with tropical-storm-force winds extending up to 240 n mi southeast of the center. Ernesto continues to move north-northeast, estimated at 330/12 kt. The deep-layer trough that has been initially influencing Ernesto`s motion is already starting to leave the tropical cyclone behind, and the track guidance indicates the hurricane will begin to slow its forward motion over the next day or so while continuing to move north-northeastward. After that time, another shortwave trough currently over the upper Midwest U.S. is forecast to dig southeastward, which should ultimately result in Ernesto accelerating northeastward around the periphery of the subtropical ridge to its southeast. The track guidance this cycle is quite close to the prior forecast, and the NHC track forecast only has minor changes compared to the previous cycle. Vertical wind shear diagnosed by SHIPS guidance is already up to 25 kt or greater, and this shear is likely to persist for another 12 to 24 h. Thus the latest NHC intensity forecast now shows a little more weakening, though it should be noted some of the hurricane regional models show Ernesto weakening below hurricane intensity over the next 36 h. Thereafter, as the first trough bypasses the system, the forecast shear decreases while the tropical cyclone remains over 28 C or warmer sea surface temperatures. Thus, there remains an opportunity for Ernesto to re-intensify before it reaches the north wall of the Gulf Stream by early next week. However, extratropical transition will likely be underway shortly after it crosses over much cooler waters after 72 h, with the latest NHC forecast showing the system becoming extratropical at 96 h. Key Messages: 1. Ernesto is expected to bring a prolonged period of strong winds and storm surge on Bermuda starting this afternoon through Saturday night. A hurricane warning is in effect for the island, and preparations to protect life and property should be rushed to completion. 2. Heavy rainfall associated with Ernesto is expected to impact Bermuda through this weekend and will likely result in considerable life-threatening flash flooding, especially in low-lying areas on the island. 3. Even though Ernesto is forecast to remain well offshore the U.S. East Coast, swells generated by the hurricane are expected to affect the area through the weekend. Beach goers should be aware of a significant risk of life-threatening surf and rip currents, and stay out of the water if advised by lifeguards. Surf and rip currents are also possible on the Turks and Caicos, the Bahamas, Bermuda, and Atlantic Canada during the next few days. FORECAST POSITIONS AND MAX WINDS INIT 16/1500Z 29.5N 66.4W 85 KT 100 MPH 12H 17/0000Z 31.0N 65.5W 80 KT 90 MPH 24H 17/1200Z 32.5N 64.9W 75 KT 85 MPH 36H 18/0000Z 33.8N 64.5W 70 KT 80 MPH 48H 18/1200Z 35.4N 63.9W 70 KT 80 MPH 60H 19/0000Z 38.1N 62.5W 75 KT 85 MPH 72H 19/1200Z 41.6N 59.7W 80 KT 90 MPH 96H 20/1200Z 48.4N 47.5W 55 KT 65 MPH...POST-TROP/EXTRATROP 120H 21/1200Z 52.0N 26.0W 40 KT 45 MPH...POST-TROP/EXTRATROP $$ Forecaster Papin |
