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Hurricane Laura Forecast Discussion Number 25
2020-08-26 04:50:46| National Hurricane Center (Atlantic)
Issued at 1000 PM CDT Tue Aug 25 2020 000 WTNT43 KNHC 260250 TCDAT3 Hurricane Laura Discussion Number 25 NWS National Hurricane Center Miami FL AL132020 1000 PM CDT Tue Aug 25 2020 Laura's cloud pattern is becoming better organized on satellite images, with a banding feature over the eastern portion of the circulation and an expanding central dense overcast with cloud tops of -80C or colder. The upper-level outflow is becoming better established over the northwestern quadrant. Flight-level and SFMR-observed surface winds from NOAA and Air Force Hurricane Hunter aircraft indicate that the maximum winds have increased to near 80 kt, and the central pressure is falling. The hurricane is expected to remain over SSTs near 30 deg C until it nears the coast, with only moderate vertical shear. The SHIPS Rapid Intensification Index shows a significant probability for a 25-30 kt increase in strength during the next 24 hours, and this is reflected in the official forecast. This is also between the simple and corrected intensity model consensus predictions. Laura will weaken rapidly after landfall, but it will likely bring hurricane-force winds well inland over extreme western Louisiana and eastern Texas. Aircraft and satellite fixes show a continued west-northwestward track with an initial motion estimate near 300/15 kt. The track forecast reasoning has not changed. The hurricane should gradually turn toward the northwest and north over the next day or two as it moves around the western periphery of a mid-level high and into a weakness into the subtropical ridge. Later in the forecast period the cyclone should turn toward the east-northeast and move with increasing forward speed while embedded within the westerlies. The official track forecast is very similar to the previous one and also very close to the simple and corrected consensus track model predictions. Users are again reminded not to focus on the exact details of the track or intensity forecasts as the average NHC track error at 36 h is around 60 miles and the average intensity error is close to 10 mph. In addition, wind, storm surge, and rainfall hazards will extend far from the center. Key Messages: 1. There is a danger of life-threatening storm surge with large and dangerous waves producing potentially catastrophic damage from San Luis Pass, Texas, to the Mouth of the Mississippi River, including areas inside the Port Arthur Hurricane Flood Protection system. This surge could penetrate up to 30 miles inland from the immediate coastline in southwestern Louisiana and far southeastern Texas. Actions to protect life and property should be rushed to completion, as water levels will begin to rise on Wednesday. 2. Hurricane-force winds are expected Wednesday night in the warning area from San Luis Pass, Texas, to west of Morgan City, Louisiana, and the strongest winds associated with Laura's eyewall will occur somewhere within this area. Hurricane-force winds and widespread damaging wind gusts are also expected to spread well inland into portions of eastern Texas and western Louisiana early Thursday. 3. Widespread flash flooding along small streams, urban areas, and roadways is expected to begin Wednesday night into Thursday across far eastern Texas, Louisiana, and Arkansas. This will also lead to minor to isolated moderate 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 26/0300Z 25.2N 89.5W 80 KT 90 MPH 12H 26/1200Z 26.5N 91.4W 95 KT 110 MPH 24H 27/0000Z 28.7N 93.1W 105 KT 120 MPH 36H 27/1200Z 31.2N 93.8W 70 KT 80 MPH...INLAND 48H 28/0000Z 33.7N 93.6W 40 KT 45 MPH...INLAND 60H 28/1200Z 36.0N 92.3W 30 KT 35 MPH...INLAND 72H 29/0000Z 37.2N 89.5W 25 KT 30 MPH...INLAND 96H 30/0000Z 38.0N 78.0W 30 KT 35 MPH...POST-TROP/EXTRATROP 120H 31/0000Z 42.0N 65.0W 35 KT 40 MPH...POST-TROP/EXTRATROP $$ Forecaster Pasch
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