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Tropical Storm Laura Forecast Discussion Number 14
2020-08-23 10:59:58| National Hurricane Center (Atlantic)
Issued at 500 AM EDT Sun Aug 23 2020 000 WTNT43 KNHC 230859 TCDAT3 Tropical Storm Laura Discussion Number 14 NWS National Hurricane Center Miami FL AL132020 500 AM EDT Sun Aug 23 2020 Laura has maintained an impressive convective pattern despite the center being located over extreme south-central Dominican Republic. Numerous cloud tops of -85C to -90C have been noted over the Barahona peninsula, an indication that extremely heavy rainfall has been occurring there. The center of Laura passed over or very near Santo Domingo around 0430Z based on a noticeable wind shift that was measured at the international airport. Laura's outflow pattern has also continue to improve in all quadrants. The initial intensity of 40 kt is based on earlier scatterometer and aircraft data, along with surface observations along the north coast of the Dominican Republic. Laura has continued to move west-northwestward and the initial motion estimate is now 285/16 kt. There has been a significant westward shift in the latest NHC model guidance, which appears to be due to most of the global models taking the center of Laura farther south over central or southern Hispaniola rather than emerging it off the north coast of Haiti like the GFS is and has been forecasting. Given that the most intense convection has persisted along the southern coast of Hispaniola, that is where the most likely area that a low-level and/or mid-level circulation is most probable to develop or persist. As a result, the new NHC track forecast favors a more southerly and westerly track solution similar to the preponderance of the track guidance. However, the new forecast track has not been shifted as far to the left as the consensus models in the event that the models shift back to the north. However, the latter scenario is appearing less likely based observed satellite trends since the previous advisory. Little if any significant change in strength is expected due to Laura moving pretty much down the spine of Hispaniola and Cuba during the the next 36 hours, with the strongest wind likely remaining over water in the northeast quadrant where the pressure gradient will be the tightest between the cyclone and the Bermuda High. By 48 hours and continuing until landfall, Laura is forecast to remain in a low shear and very favorable upper-level outflow environment while passing of extremely warm SSTs near 31C. This should allow for significant strengthening to occur once the cyclone regains a decent inner core after exiting Cuba. The new NHC intensity forecast is a blend of the intensity forecasts by the GFS and ECMWF global models and the corrected consensus models HCCA and FSSE. Key Messages: 1. Tropical storm conditions are expected across portions of the Dominican Republic and Haiti, the Turks and Caicos, the southeastern Bahamas, and Cuba through Monday. Heavy rainfall is likely across these areas and could cause mudslides and flash and urban flooding. 2. Tropical storm conditions are possible the central Bahamas and Andros Island tonight and Monday, and in the Florida Keys on Monday. 3. The details of the long-range track and intensity forecasts remain uncertain since Laura is forecast to move near or over portions of the Greater Antilles through Monday. However, Laura is forecast to strengthen over the Gulf of Mexico and could bring storm surge, rainfall, and wind impacts to portions of the U.S. Gulf Coast by the middle of next week. This could result in a prolonged period of hazardous weather for areas that are likely to be affected by Tropical Storm Marco earlier in the week. Interests there should monitor the progress of Laura and Marco and updates to the forecast during the next few days. FORECAST POSITIONS AND MAX WINDS INIT 23/0900Z 18.8N 70.9W 40 KT 45 MPH 12H 23/1800Z 19.8N 73.7W 40 KT 45 MPH...OVER WATER 24H 24/0600Z 20.9N 77.5W 40 KT 45 MPH...INLAND 36H 24/1800Z 22.2N 81.1W 40 KT 45 MPH...INLAND 48H 25/0600Z 23.5N 84.2W 45 KT 50 MPH...OVER WATER 60H 25/1800Z 24.9N 87.0W 60 KT 70 MPH 72H 26/0600Z 26.4N 89.4W 75 KT 85 MPH 96H 27/0600Z 29.9N 92.5W 85 KT 100 MPH 120H 28/0600Z 35.0N 91.4W 30 KT 35 MPH...INLAND $$ Forecaster Stewart
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