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Tropical Storm Laura Forecast Discussion Number 17
2020-08-24 04:45:40| National Hurricane Center (Atlantic)
Issued at 1100 PM EDT Sun Aug 23 2020 000 WTNT43 KNHC 240245 TCDAT3 Tropical Storm Laura Discussion Number 17 NWS National Hurricane Center Miami FL AL132020 1100 PM EDT Sun Aug 23 2020 Radar data from Cuba and satellite images indicate that Laura continues to gradually become better organized. Convection is quite deep on the south side of the circulation, and rainfall is likely very heavy over portions of eastern Cuba and Jamaica. A surface observation from Guantanamo Bay, Cuba, measured sustained winds of 52 kt with a wind gust to 63 kt a few hours ago. Based on this observation and the system's improved structure, the initial intensity is nudged up to 55 kt. Laura continues to move swiftly to the west-northwest on the south side of a strong subtropical ridge, with the initial motion estimated to be 285/18 kt. The subtropical high is expected to expand westward during the next couple of days, and that should keep Laura moving fairly quickly to the west-northwest near or over Cuba through Monday and then across the south-central Gulf of Mexico on Tuesday. The models suggest that a gradual turn to the northwest is likely by early Wednesday as the storm nears the western side of the ridge, followed by a northward motion after that. The details of the northwest and north turn are quite important when trying to figure out where the core of Laura is going to make landfall. However, at this time there is still a notable spread in the models and their ensemble members, meaning that it is still unclear exactly where the worst weather conditions will occur. The NHC track forecast is little changed from earlier and near the consensus aids. This forecast shows landfall along the northern Gulf coast in about 3 days. The tropical storm is expected to move very near or over the entire island of Cuba through Monday, and the interaction with the island should limit strengthening during that time. However, significant intensification is expected when the storm moves over the Gulf of Mexico due to a combination of favorable conditions of low wind shear, high moisture, and warm SSTs. The NHC intensity forecast is largely an update of the previous one and lies near the middle of the guidance envelope. Although not explicitly forecast, 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 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, winds, storm surge, and rainfall hazards will extend far from the center. Key Messages: 1. Tropical storm conditions are expected across much of Cuba through Monday. Heavy rainfall is likely across Cuba and Jamaica through Monday and these rains could cause mudslides and life-threatening flash and urban flooding. Tropical storm conditions are expected in the Dry Tortugas on Monday. 2. Tropical storm conditions are possible over the Middle and Lower Florida Keys 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 couple of days. FORECAST POSITIONS AND MAX WINDS INIT 24/0300Z 20.1N 76.6W 55 KT 65 MPH...NEAR CUBA 12H 24/1200Z 21.1N 79.4W 55 KT 65 MPH...NEAR CUBA 24H 25/0000Z 22.5N 82.6W 60 KT 70 MPH...NEAR CUBA 36H 25/1200Z 23.8N 85.7W 65 KT 75 MPH 48H 26/0000Z 25.3N 88.5W 70 KT 80 MPH 60H 26/1200Z 27.1N 90.9W 80 KT 90 MPH 72H 27/0000Z 29.2N 92.4W 90 KT 105 MPH...NEAR THE COAST 96H 28/0000Z 34.2N 90.9W 40 KT 45 MPH...INLAND 120H 29/0000Z 37.4N 83.7W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Cangialosi
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