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Hurricane Laura Forecast Discussion Number 23
2020-08-25 17:05:38| National Hurricane Center (Atlantic)
Issued at 1000 AM CDT Tue Aug 25 2020 000 WTNT43 KNHC 251505 TCDAT3 Hurricane Laura Discussion Number 23 NWS National Hurricane Center Miami FL AL132020 1000 AM CDT Tue Aug 25 2020 Satellite imagery shows that Laura has become a little better organized since it crossed western Cuba, and it now has a central dense overcast and some outer banding in the southern quadrant. Reports from Air Force Reserve and NOAA Hurricane Hunter aircraft included SFMR winds of near 65 kt, 700-mb flight-level winds as high as 77 kt, and a central pressure near 990 mb. Based on these data, Laura has been upgraded to a hurricane with an initial intensity of 65 kt. The initial motion is west-northwestward or 290/14 kt. The hurricane is currently on the south side of a large-deep layer ridge over the southeastern United States, and it is moving toward a break in the ridge caused by mid- to -upper-level troughing over Texas and the southern Great Plains. The current and forecast synoptic pattern should steer Laura west-northwestward today followed by a turn toward the northwest tonight and toward the north by Wednesday night and Thursday. This will result in the hurricane making landfall in the area of southwestern Louisiana or the upper Texas coast late Wednesday night or Thursday morning. The new forecast track before landfall has been nudged a little to the west of the previous track in response to a westward nudge in the guidance. However, it still lies a little east of the consensus models at the time of landfall. After landfall, Laura is expected to recurve into the westerlies and move eastward through the Tennessee Valley and the mid-Atlantic States. The hurricane currently looks a little ragged, with little or no convection outside of the central dense overcast and the southern quadrant banding. This may be due to dry air in the vicinity and some light northerly shear. Conditions appear generally favorable for strengthening during the next 36 h, and the new intensity forecast calls for Laura to become a major hurricane during this time. The global model are in good agreement that the hurricane should encounter increasing shear in the last 12 h before landfall, although the potential impacts on the landfall intensity are unclear. After landfall, Laura should weaken through the 96 h point. After that, some re-intensification is expected as the storm becomes extratropical. Users are again reminded not to focus on the exact details of the track or intensity forecasts as the average NHC track error at 48 h is around 80 miles and the average intensity error is close to 15 mph. In addition, wind, storm surge, and rainfall hazards will extend far from the center. Key Messages: 1. Laura is forecast to reach the northwestern Gulf Coast at or near major hurricane intensity Wednesday night. Do not focus on the details of the official forecast given the typical uncertainty in NHC's track and intensity predictions. Storm surge, wind, and rainfall hazards will extend well away from Laura's center along the Gulf Coast. 2. There is the danger of life-threatening storm surge accompanied by large and dangerous waves from San Luis Pass, Texas, to the Mouth of the Mississippi River, including areas inside the Port Arthur Hurricane Flood Protection system. A Storm Surge Warning is in effect and residents should follow any advice given by local officials. Actions to protect life and property should be rushed to completion today, as water levels will begin to rise Wednesday. 3. Hurricane conditions are expected by Wednesday evening in the area from San Luis Pass, Texas, to west of Morgan City, Louisiana, and a Hurricane Warning is in effect. Tropical storm conditions are expected to begin in the warning area Wednesday afternoon. 4. The threat of widespread flash and urban flooding along with small streams overflowing their banks will be increasing Wednesday night into Thursday from far eastern Texas, across Louisiana, and Arkansas. This will also lead to minor to isolated moderate river flooding. The heavy rainfall threat will spread northeastward into the middle-Mississippi, lower Ohio, and Tennessee Valleys Friday and Saturday. FORECAST POSITIONS AND MAX WINDS INIT 25/1500Z 23.7N 87.0W 65 KT 75 MPH 12H 26/0000Z 24.6N 89.2W 75 KT 85 MPH 24H 26/1200Z 26.0N 91.5W 90 KT 105 MPH 36H 27/0000Z 28.0N 93.3W 100 KT 115 MPH 48H 27/1200Z 30.5N 93.9W 80 KT 90 MPH...INLAND 60H 28/0000Z 33.1N 93.6W 45 KT 50 MPH...INLAND 72H 28/1200Z 35.2N 92.1W 30 KT 35 MPH...INLAND 96H 29/1200Z 37.5N 83.5W 25 KT 30 MPH...INLAND 120H 30/1200Z 40.5N 69.5W 40 KT 45 MPH...POST-TROP/EXTRATROP $$ Forecaster Beven
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