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Subtropical Storm Alberto Forecast Discussion Number 9
2018-05-27 16:38:12| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT Sun May 27 2018 000 WTNT41 KNHC 271438 TCDAT1 Subtropical Storm Alberto Discussion Number 9 NWS National Hurricane Center Miami FL AL012018 1100 AM EDT Sun May 27 2018 The satellite and radar presentation of Alberto has improved markedly over the past 12 hours or so. Deep convection has increased and become organized in a primary band that wraps around the western and northwestern portions of the storm and the circulation has also become much better defined than 24 hours ago. An Air Force Reserve reconnaissance aircraft has recently indicated that the pressure has fallen to 994 mb. The aircraft has also reported peak flight-level winds of 49 kt and believable SFMR winds of around 40 kt, however, the aircraft has not yet sampled the northwestern portion of the circulation where the deepest convection is located. Assuming that there are slightly higher winds in that area, the initial intensity has been increased to 45 kt. With deep convection closer to the center and a slightly smaller radius of maximum winds, it appears that Alberto is beginning its transition to a tropical cyclone. The reconnaissance aircraft data also indicate that a shallow warm core is present. It is likely that Alberto will make the transition to tropical storm later today or tonight. As this transition occurs, some additional strengthening is forecast while Alberto moves over marginally warm sea surface temperatures and the shear relaxes. However, dry mid- level air wrapping around the eastern portion of the circulation could slow the intensification process before Alberto reaches the coast. The initial motion estimate of 005/12 is again highly uncertain due to the center re-formations that have occurred over the past 12 to 24 hours. The cyclone should move generally northward today, then turn northwestward around the northeastern side of a cutoff low over the central Gulf of Mexico. The timing and location of landfall of the center will be dependent on when the northwestward turn occurs. The latest ECMWF forecast moves Alberto faster northward before it makes the turn and therefore brings the center onshore much sooner and farther eastward than the UKMET and GFS. The NHC forecast is near the model consensus, and is somewhat faster than the previous advisory. Users should remember not to focus on the exact timing and location of landfall since wind and rain will continue to spread northward over the northeastern Gulf Coast well ahead of the center. KEY MESSAGES: 1. Alberto is expected to produce heavy rainfall with a risk of flooding and flash flooding over western Cuba, the Florida Keys, and south Florida today. The risk for heavy rainfall and flooding will then spread over much of the southeast U.S. tonight and Monday. 2. Hazardous storm surge is possible along portions of the eastern Gulf Coast beginning later today, including areas well east of the track of Alberto's center. Residents in the storm surge watch area are encouraged to follow any guidance given by their local government officials. 3. Tropical storm conditions are likely within the tropical storm warning area along the Florida west coast today and within the warning area along the northern Gulf Coast by tonight. 4. Dangerous surf and rip current conditions will continue to affect portions of the eastern and northern Gulf Coast through Monday. FORECAST POSITIONS AND MAX WINDS INIT 27/1500Z 27.1N 84.4W 45 KT 50 MPH 12H 28/0000Z 28.7N 84.9W 50 KT 60 MPH...TROPICAL STORM 24H 28/1200Z 30.3N 85.9W 50 KT 60 MPH...INLAND 36H 29/0000Z 31.6N 86.4W 35 KT 40 MPH...INLAND 48H 29/1200Z 33.6N 86.7W 25 KT 30 MPH...INLAND 72H 30/1200Z 38.3N 87.2W 20 KT 25 MPH...INLAND 96H 31/1200Z 43.3N 84.7W 15 KT 15 MPH...POST-TROP/REMNT LOW 120H 01/1200Z 46.5N 79.5W 15 KT 15 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown
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