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Subtropical Storm Alberto Forecast Discussion Number 8
2018-05-27 10:49:41| National Hurricane Center (Atlantic)
Issued at 500 AM EDT Sun May 27 2018 000 WTNT41 KNHC 270849 TCDAT1 Subtropical Storm Alberto Discussion Number 8 NWS National Hurricane Center Miami FL AL012018 500 AM EDT Sun May 27 2018 Alberto appears a little better organized this morning with an area of deep convection gradually expanding near and to the north of the center. A large band of showers and thunderstorms extends well to the east of the center from western Cuba to south Florida and the northwestern Bahamas. Despite the improved organization, a fairly recent ASCAT pass showed maximum winds of about 35 kt, and therefore, the initial wind speed is held at that value. Based on the system's structure, it still appears to be subtropical, but it is gaining some more tropical characteristics. An Air Force Hurricane Hunter aircraft is scheduled to investigate Alberto later this morning, and should provide a better assessment of its intensity and structure. The initial motion of 015/11 is highly uncertain since the center of the storm has been re-forming and wobbling around. In fact, another center re-formation can not be ruled out since Doppler radar images show a pronounced mid-level circulation to the northeast of the low-level center. Alberto is expected to turn northward later today and then northwestward tonight as it moves around the eastern side of a cutoff mid- to upper-level low over the central Gulf of Mexico. After Alberto merges with the upper low, a turn back to the north is forecast by Monday night and Tuesday. The latest model guidance has shifted notably to the right, and the NHC track forecast has been adjusted by about 30 n mi in that direction. The eastward shift necessitates extending the tropical storm warning along the Gulf coast of Florida. Even though Alberto has not yet strengthened, slow intensification seems likely until it reaches the coastline on Monday. The reasons for intensification consist of diffluence associated with a negatively tilted upper-level trough, lower shear, and marginally warm waters in the Gulf of Mexico. However, the intensity models show a weaker solution this cycle, perhaps because the center may move inland a little sooner, and no model shows Alberto reaching hurricane strength. Based on this guidance, the NHC forecast has been lowered slightly, but it still lies near the high end of the model predictions. Alberto is likely to complete its transition to a tropical storm within 24 hours when it moves into an area of light shear, which should allow the cyclone to develop a deeper warm core and become more symmetric. 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 through the day. The risk for heavy rainfall and flooding will then spread over many parts of the southeast U.S. tonight and Monday. 2. Hazardous storm surge is possible along portions of the central and 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 likely spread northward along the eastern and northern Gulf Coast through Monday. FORECAST POSITIONS AND MAX WINDS INIT 27/0900Z 25.0N 84.2W 35 KT 40 MPH 12H 27/1800Z 26.8N 84.4W 40 KT 45 MPH 24H 28/0600Z 28.6N 85.2W 45 KT 50 MPH...TROPICAL STORM 36H 28/1800Z 30.0N 86.0W 50 KT 60 MPH...TROPICAL STORM 48H 29/0600Z 31.7N 86.3W 35 KT 40 MPH...INLAND 72H 30/0600Z 36.2N 86.8W 20 KT 25 MPH...INLAND 96H 31/0600Z 41.1N 85.1W 15 KT 15 MPH...POST-TROP/REMNT LOW 120H 01/0600Z 45.0N 80.5W 15 KT 15 MPH...POST-TROP/REMNT LOW $$ Forecaster Cangialosi
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