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Subtropical Storm ALBERTO


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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

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