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Tropical Storm Laura Forecast Discussion Number 19
2020-08-24 16:40:51| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT Mon Aug 24 2020 000 WTNT43 KNHC 241440 TCDAT3 Tropical Storm Laura Discussion Number 19 NWS National Hurricane Center Miami FL AL132020 1100 AM EDT Mon Aug 24 2020 Laura's satellite presentation has degraded somewhat since yesterday, however, there has been a recent increase in convection near the center, and a large band over the southern periphery of the circulation. It appears that the combination of land interaction, moderate northerly shear, and some dry air has caused the change in structure. NOAA and Air Force reconnaissance aircraft have reported several believable SFMR winds in the 45-50 kt range and a minimum pressure of around 1002 kt. Based on these observations, the initial wind speed has been set at 50 kt. Laura is forecast to pass over the very warm water of the extreme northwestern Caribbean Sea just south of the coast of Cuba today, and some modest strengthening is possible before the center moves over the western portion of Cuba this evening. Laura is then forecast to emerge over the southeastern Gulf of Mexico overnight where a combination of warm sea surface temperatures and a favorable upper-level environment are expected to allow for steady strengthening. Given the very conducive upper-level wind pattern depicted by the global models, a period of rapid strengthening is possible once Laura re-organizes an inner core after its passage over western Cuba. The regional hurricane models remain quite bullish on intensification, and the GFS and UKMET models indicate significant deepening while Laura moves over the Gulf of Mexico. The statistical guidance is not as aggressive, and the NHC forecast is in good agreement with the intensity consensus aids which lie between the higher solutions of the regional models and the SHIPS and LGEM guidance. Laura has been moving on a steady west-northwestward track over the past day or so, and the initial motion estimate is 285/17 kt. The deep-layer ridge over the western Atlantic is forecast to build westward over the eastern Gulf of Mexico during the next day or so, and this should keep Laura on a west-northwestward heading through Tuesday. After that time, a mid- to upper-level trough over the south-central United States should produce a break in the ridge over the western Gulf of Mexico. Laura should turn northwestward Tuesday night in response to the break in the ridge, and the storm is expected to reach the northwestern Gulf coast Wednesday night. The cyclone should become embedded within the mid-latitude westerlies by day 4, and Laura or its remnants should recurve to the northeast and east-northeast by the end of the period. Although the track guidance is in somewhat better agreement today, there remains some cross-track spread by day 3, with the UKMET showing landfall well southwest of the official forecast. The NHC track is close to the various consensus aids and leans toward the typically reliable GFS and ECMWF models. Users are again reminded to not to focus on the exact details of the track or intensity forecasts as the average NHC track error at 72 h is around 100 miles and the average intensity error is around 15 mph (13 kt). In addition, wind, storm surge, and rainfall hazards will extend far from the center. Key Messages: 1. Tropical storm conditions are expected across much of Cuba today. Heavy rainfall is likely across Cuba and Jamaica today, and these rains could cause mudslides and life-threatening flash and urban flooding. Tropical storm conditions are expected in the Dry Tortugas, and the Middle and Lower Florida Keys later today. 2. There is an increasing risk of dangerous storm surge, wind, and rainfall impacts from the upper Texas coast through the north- central Gulf Coast beginning on Wednesday. Interests in these areas should monitor the progress of Laura and ensure they have their hurricane plan in place, as storm surge and hurricane watches will likely be issued later today. FORECAST POSITIONS AND MAX WINDS INIT 24/1500Z 21.2N 80.6W 50 KT 60 MPH 12H 25/0000Z 22.2N 82.9W 55 KT 65 MPH 24H 25/1200Z 23.6N 86.0W 60 KT 70 MPH 36H 26/0000Z 25.2N 88.8W 70 KT 80 MPH 48H 26/1200Z 26.8N 91.1W 80 KT 90 MPH 60H 27/0000Z 28.7N 92.8W 90 KT 105 MPH 72H 27/1200Z 31.2N 93.3W 65 KT 75 MPH...INLAND 96H 28/1200Z 36.0N 90.9W 30 KT 35 MPH...INLAND 120H 29/1200Z 37.5N 81.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown
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