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Hurricane Laura Forecast Discussion Number 27
2020-08-26 17:15:56| National Hurricane Center (Atlantic)
Issued at 1000 AM CDT Wed Aug 26 2020 000 WTNT43 KNHC 261515 CCA TCDAT3 Hurricane Laura Discussion Number 27...Corrected NWS National Hurricane Center Miami FL AL132020 1000 AM CDT Wed Aug 26 2020 Corrected 24-h status in forecast table to inland. Laura has become a very powerful hurricane this morning. The satellite presentation has continued to improve with the eye becoming better defined, and cloud tops colder than -70C in the surrounding ring of deep convection. Both NOAA and Air Force hurricane hunter aircraft have provided valuable data this morning. The NOAA P-3 aircraft reported a peak flight-level wind of 125 kt at 8000 ft, and a peak SFMR wind of 104 kt, while the Air Force crew has observed peak 700-mb flight-level winds of 121 kt and peak SFMR winds of 104 kt. The lastest minimum pressure estimated from aircraft data is 956 mb, indicating a pressure drop of 27 mb over the past 12 hours. Based on the aircraft data, the initial wind speed was increased to 100 kt on the 1200 UTC intermediate advisory, and is now set at 110 kt based on the latest flight-level and SFMR winds. Laura is likely to continue strengthening today while it moves over warm waters of the northwestern Gulf of Mexico and the vertical wind shear remains low. Laura's intensity could level-off by this evening due to the possibility of an eyewall replacement cycle and the expected increase in shear around the time of landfall. Even if the rate of strengthening eases, Laura is expected to be an extremely powerful category 4 hurricane when it reaches the northwestern Gulf coast. After landfall, rapid weakening will occur, but Laura will bring a swath of damaging winds well inland over western Louisiana and eastern Texas. The UKMET and ECMWF models suggest that there is some chance that Laura re-intensifies as a tropical cyclone off the mid-Atlantic coast, but given the uncertainties at that time range the forecast continues to show it as a post-tropical cyclone at days 4 and 5. Laura is moving northwestward at about 13 kt. A gradual turn toward the north-northwest and north are expected within the next 12-18 hours as the hurricane moves around the western portion of a mid- level ridge that extends from the western Atlantic into the southeastern United States. This motion will bring the center of Laura onshore in southwestern Louisiana or extreme eastern Texas tonight. By Thursday night, Laura is forecast to turn northeastward, and then east-northeastward on Friday as it becomes embedded in the mid-latitude westerlies. The dynamical track models are in good agreement, and little adjustment to the previous NHC forecast track was required. Laura is a large hurricane and users are reminded to not focus on the precise track forecast since wind, storm surge, and rainfall hazards extend far from the center. Key Messages: 1. Unsurvivable storm surge with large and destructive waves will cause catastrophic damage from Sea Rim State Park, Texas, to Intracoastal City, Louisiana, including Calcasieu and Sabine Lakes. This surge could penetrate up to 30 miles inland from the immediate coastline. Only a few hours remain to protect life and property and all actions should be rushed to completion. 2. Hurricane-force winds are expected tonight in portions of the hurricane warning area from San Luis Pass, Texas, to west of Morgan City, Louisiana, with catastrophic wind damage expected where Laura's eyewall makes landfall. Hurricane-force winds and widespread damaging wind gusts will spread well inland across portions of eastern Texas and western Louisiana early Thursday. 3. Widespread flash flooding along small streams, urban areas, and roadways is expected to begin this afternoon into Thursday from far eastern Texas, across Louisiana and Arkansas. This will also lead to minor to isolated moderate freshwater river flooding. The heavy rainfall threat and localized flash and urban flooding potential will spread northeastward into the middle-Mississippi, lower Ohio and Tennessee Valleys Friday night and Saturday. FORECAST POSITIONS AND MAX WINDS INIT 26/1500Z 27.0N 92.0W 110 KT 125 MPH 12H 27/0000Z 28.5N 93.2W 125 KT 145 MPH 24H 27/1200Z 31.0N 93.8W 75 KT 85 MPH...INLAND 36H 28/0000Z 33.7N 93.5W 40 KT 45 MPH...INLAND 48H 28/1200Z 35.8N 92.2W 25 KT 30 MPH...INLAND 60H 29/0000Z 37.2N 89.1W 25 KT 30 MPH...INLAND 72H 29/1200Z 37.6N 83.9W 25 KT 30 MPH...INLAND 96H 30/1200Z 40.0N 70.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 31/1200Z 48.0N 55.0W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Brown
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