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Subtropical Storm ALBERTO
ZCZC MIATCDAT1 ALL TTAA00 KNHC DDHHMM Subtropical Storm Alberto Discussion Number 6 NWS National Hurricane Center Miami FL AL012018 400 PM CDT Sat May 26 2018 Before departing the storm, the Air Force Reserve Hurricane Hunter aircraft flew near the low-level cloud swirl that became apparent in visible satellite imagery over the southeastern Gulf of Mexico late this morning. Data from the plane indicate that the center had reformed in that location and that the pressure had fallen to 999 mb. The aircraft did not sample the area to the east of the new center, but based on recent satellite classifications and surface observations the initial intensity remains 35 kt for this advisory. The primary mechanism for intensification appears to be a shortwave trough moving southeastward into the larger negatively tilted trough over the eastern Gulf, which should cause a cutoff low to form during the next 24 hours. This is expected to result in deepening of Alberto while it moves generally northward over the Gulf of Mexico on Sunday and Sunday night. The shear is forecast to decrease as Alberto become co-located with the upper-level low and the system could transition to a more tropical cyclone-like structure before landfall. The NHC intensity forecast once again calls for steady strengthening through 36 h, but shows little strengthening after that time due to the possibility of dry air intrusion. The system has moved generally northward during the past 24 hours, however, the reformation of the center today makes the initial motion estimate more uncertain than normal. Alberto should move northward to north-northeastward tonight, and then turn north-northwestward and decelerate on Sunday and Sunday night as it moves around the eastern side of the trough/cutoff low. The dynamical models remain in good agreement on this scenario but have shifted eastward once again. The interpolated guidance models lie a bit west of the model fields due to the more northwestward 1800 UTC initial position of Alberto. As a result, the NHC track is along the eastern edge of the guidance envelope as a compromise between the ECMWF/GFS model fields and trackers. The new NHC track forecast has required the issuance of a Tropical Storm Warning for a portion of the west coast of Florida and a Tropical Storm Warning for a portion of the northern Gulf Coast. KEY MESSAGES: 1. Regardless of its exact track and intensity, Alberto is expected to produce heavy rainfall and flash flooding over western Cuba, southern Florida and the Florida Keys. Rainfall and flooding potential will increase across the central U.S. Gulf Coast region and over much of the southeastern United States beginning Sunday and will continue into next week. 2. Tropical-storm-force winds and hazardous storm surge are possible along portions of the central and eastern U.S. Gulf Coast beginning on Sunday, including areas well east of the track of Alberto's center. Residents in the warning and watch areas are encouraged not to focus on the details of the forecast track of Alberto and should follow any guidance given by their local government officials. 3. 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 26/2100Z 23.3N 85.1W 35 KT 40 MPH 12H 27/0600Z 25.4N 84.9W 45 KT 50 MPH 24H 27/1800Z 27.5N 85.3W 50 KT 60 MPH 36H 28/0600Z 28.9N 86.3W 55 KT 65 MPH...TROPICAL STORM 48H 28/1800Z 30.0N 87.0W 55 KT 65 MPH...TROPICAL STORM 72H 29/1800Z 33.6N 87.9W 30 KT 35 MPH...INLAND 96H 30/1800Z 38.3N 87.5W 20 KT 25 MPH...INLAND 120H 31/1800Z 42.4N 83.4W 15 KT 15 MPH...POST-TROPICAL $$ Forecaster Brown NNNN