000
WTNT41 KNHC 260853
TCDAT1

Subtropical Storm Alberto Discussion Number   4
NWS National Hurricane Center Miami FL       AL012018
400 AM CDT Sat May 26 2018

Alberto is not very well organized this morning.  Satellite images
indicate that the low-level center is located between widespread
showers and thunderstorms well to its northeast and patches of deep
convection to its south and east.  The struggling cyclone continues
to battle westerly shear and dry air.  A recent ASCAT pass indicated
that winds near the center were not particularly strong. The initial
intensity is held at a possibly generous 35 kt pending a sampling of
the circulation farther east by an Air Force reconnaissance aircraft
in a few hours.  Alberto remains subtropical given its sprawling
structure and involvement with an upper-level trough.

The subtropical storm has now turned north-northeastward at an
estimated speed of 6 kt.  This general motion with a increase in
forward speed is expected throughout the day today, taking the
center of Alberto through the Yucatan Channel.  A turn to the
northwest is forecast on Sunday as the storm rotates around a
developing mid- to upper-level low in the central Gulf of Mexico.
Alberto is predicted to be very near the northern Gulf Coast in
about 72 hours, and should then turn northward and northeastward
when it moves inland over the eastern U.S.  The models are in
fairly good agreement this cycle, but they have trended a bit faster
from previous runs.  The NHC track forecast has been adjusted
accordingly, and lies fairly close to the latest consensus aids.

Only slow strengthening is expected today due to the broad nature
of the system and continued influences of westerly shear and dry
air.  There is an opportunity for more significant strengthening
tonight and Sunday when the shear is expected to lessen and
Alberto moves into a region of upper-level diffluence while it
remains over warm SSTs.  The models also suggest that Alberto will
likely make a transition to a tropical storm in about 36 hours, and
that is reflected in the official forecast below.  The official
intensity forecast is fairly similar to the previous one, and is in
line with the IVCN and HCCA consensus models.

The HMON model is now the only intensity guidance that makes
Alberto a hurricane before it reaches the coast.  Although a
hurricane watch could still be required for a portion of the Gulf
Coast later today, the recent intensity guidance trends suggest
that this possibility is decreasing.


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.

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  26/0900Z 19.9N  85.6W   35 KT  40 MPH
 12H  26/1800Z 21.6N  85.1W   35 KT  40 MPH
 24H  27/0600Z 24.3N  85.0W   40 KT  45 MPH
 36H  27/1800Z 26.2N  85.9W   50 KT  60 MPH...TROPICAL STORM
 48H  28/0600Z 27.5N  86.8W   55 KT  65 MPH...TROPICAL STORM
 72H  29/0600Z 30.4N  87.9W   50 KT  60 MPH...NEAR THE COAST
 96H  30/0600Z 33.3N  88.1W   25 KT  30 MPH...INLAND
120H  31/0600Z 38.0N  85.0W   20 KT  25 MPH...INLAND

$$
Forecaster Cangialosi/Berg