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Subtropical Storm Alberto Forecast Discussion Number 5
2018-05-26 16:45:02| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT Sat May 26 2018 000 WTNT41 KNHC 261444 TCDAT1 Subtropical Storm Alberto Discussion Number 5 NWS National Hurricane Center Miami FL AL012018 1100 AM EDT Sat May 26 2018 There has been an increase in convection to the east and southeast of the center of Alberto this morning, however, the overall organization of the system has not changed much. Visible satellite imagery and recent reconnaissance aircraft data suggest that the circulation is somewhat elongated and a new low-level center could be forming just northwest of the western tip of Cuba. As suggested by the global models there could be several re-formations of or a discontinuity in the track of the low-level center today. Although there have been no recent observations to support the 35-kt intensity, the intensity is held at that value since the aircraft has not sampled the area well east of the center and due to the overall increase in convection. A shortwave trough dropping southeastward over the northwestern Gulf of Mexico is expected to sharpen the larger negatively tilted trough over the eastern Gulf, which is expected to cause the cyclone to deepen during the next 24 to 36 hours. This trend is consistent with the global model guidance which unanimously strengthen Alberto through Sunday. After that time, Alberto is expected to be co-located with the upper-level low which should result in some decrease in shear and a possible transition to a more tropical cyclone-like structure. The NHC intensity forecast calls for steady strengthening, but only the ECMWF-based SHIPS guidance brings Alberto near hurricane strength before landfall. Steady weakening should occur after the center moves inland. Alberto is moving northward to north-northeastward at about 9 kt. The cyclone should continue on this general heading today, but it is expected to turn north-northwestward and slow down on Sunday and Sunday night as it interacts with the mid- to upper-level trough/low over the Gulf. The track guidance has shifted slightly eastward this cycle and the NHC forecast has been adjusted accordingly. The new NHC track is near a blend of the ECMWF and GFS models, but it is not as far east as the UKMET or the TVCA multi-model consensus. The eastward adjustment in the track forecast has required the issuance of a tropical storm watch for a portion of the west coast of Florida and an eastward nudge of the watch along the coast of the Florida panhandle. 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, and tropical storm and storm surge watches are in effect for portions of these areas. Residents in the 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 are affecting portions of the Yucatan Peninsula and western Cuba and will likely spread along the eastern and central U.S. Gulf Coast later today and tonight. FORECAST POSITIONS AND MAX WINDS INIT 26/1500Z 21.6N 84.9W 35 KT 40 MPH 12H 27/0000Z 23.8N 84.6W 40 KT 45 MPH 24H 27/1200Z 26.0N 85.1W 45 KT 50 MPH 36H 28/0000Z 27.4N 86.0W 50 KT 60 MPH...TROPICAL CYCLONE 48H 28/1200Z 28.7N 86.6W 55 KT 65 MPH...TROPICAL CYCLONE 72H 29/1200Z 31.6N 87.7W 40 KT 45 MPH...INLAND 96H 30/1200Z 35.6N 88.2W 25 KT 30 MPH...INLAND 120H 31/1200Z 39.0N 85.0W 20 KT 25 MPH...INLAND $$ Forecaster Brown
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