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Subtropical Storm ALBERTO


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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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