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| #1013513 (Received by flhurricane at: 5:00 PM 23.Aug.2020) TCDAT3 Tropical Storm Laura Discussion Number 16 NWS National Hurricane Center Miami FL AL132020 500 PM EDT Sun Aug 23 2020 Satellite imagery and radar data from eastern Cuba show that the center of Laura has been moving over water between Haiti and eastern Cuba this afternoon. There has been a recent uptick in convection near the center and the radar imagery has shown an increase in banding. An Air Force reconnaissance aircraft investigating Laura this afternoon has reported a minimum pressure that has fallen to around 1000 mb, and winds to support an intensity of 50 kt. The plane very recently found a small area of stronger flight-level winds, but these winds may be associated with mesocyclone, and not representative of the large scale circulation. Laura continues to move briskly west-northwestward or 285/18 kt. The track forecast reasoning remains the same as the previous advisory. Laura should continue to move west-northwestward to the south of a deep-layer ridge that is forecast to build westward across Florida and the eastern Gulf of Mexico during the next day or two. The track guidance has continued to edge southward for the portion of the forecast near Cuba, and the NHC forecast has again been moved in that direction. Laura should continue moving west-northwestward over the southeastern Gulf on Tuesday, but a turn toward the northwest is expected Tuesday night as the cyclone nears the western portion of the ridge. A northwestward to north-northwestward motion should then continue around the western portion of the ridge until the cyclone reaches the northwestern Gulf coast. The latest run of the ECMWF has shifted significantly eastward, however its ensemble mean and many of the stronger ensemble members remain farther west as a stronger cyclone is likely to be steered more westward by the deep-layer ridge. The GFS, UKMET, and HWRF remain close to the previous NHC track, so little change was made to the official forecast was made after 48 hours. The intensity forecast during the next 24 hours is highly dependent on the track and the amount of interaction Laura has with Cuba. If the storm stays along the southern coast or just offshore, the environment of warm water and low vertical wind shear could allow for some slight strengthening, but little overall change in intensity is indicated during the next 24 hours. After the center clears western Cuba, the upper-level wind pattern is predicted to quite favorable while the storm traverses the warm waters of the Gulf of Mexico. The GFS, UKMET, and regional hurricane models all indicate significant deepening, and the NHC intensity forecast has been adjusted slightly upward. Although not explicitly shown, Laura could threaten the northwestern Gulf coast near major hurricane strength. Users are again reminded to not to focus on the exact details of the track or intensity forecast at the longer range as winds, storm surge, and rainfall hazards will extend far from the center. Key Messages: 1. Tropical storm conditions are expected across portions of the Haiti, the southeastern Bahamas, and Cuba through Monday. Heavy rainfall is likely across Haiti, Cuba, and Jamaica through Monday and these rains could cause mudslides and life-threatening flash and urban flooding. 2. Tropical storm conditions are possible over the Middle and Lower Florida Keys and the Dry Tortugas on Monday. 3. While the details of the long-range track and intensity forecasts remain uncertain, Laura is forecast to strengthen over the Gulf of Mexico and there is an increasing risk of dangerous storm surge, wind, and rainfall impacts along portions of the U.S. Gulf Coast by the middle of the week. This could result in a prolonged period of hazardous weather for areas that are likely to be affected by Marco. Interests along the Gulf Coast should monitor the progress of Laura and Marco and updates to the forecast during the next few days. FORECAST POSITIONS AND MAX WINDS INIT 23/2100Z 19.5N 75.2W 50 KT 60 MPH 12H 24/0600Z 20.6N 78.3W 50 KT 60 MPH...NEAR CUBA 24H 24/1800Z 21.8N 81.7W 50 KT 60 MPH...NEAR CUBA 36H 25/0600Z 23.3N 84.9W 55 KT 65 MPH...OVER WATER 48H 25/1800Z 24.7N 87.7W 60 KT 70 MPH 60H 26/0600Z 26.1N 90.2W 75 KT 85 MPH 72H 26/1800Z 28.0N 92.5W 90 KT 105 MPH 96H 27/1800Z 32.7N 93.5W 45 KT 50 MPH...INLAND 120H 28/1800Z 37.0N 88.0W 25 KT 30 MPH...POST-TROPICAL $$ Forecaster Brown |