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Subtropical Storm Alberto Discussion Number 8
NWS National Hurricane Center Miami FL AL012018
500 AM EDT Sun May 27 2018
Alberto appears a little better organized this morning with an area
of deep convection gradually expanding near and to the north of the
center. A large band of showers and thunderstorms extends well to
the east of the center from western Cuba to south Florida and the
northwestern Bahamas. Despite the improved organization, a fairly
recent ASCAT pass showed maximum winds of about 35 kt, and
therefore, the initial wind speed is held at that value. Based on
the system's structure, it still appears to be subtropical, but it
is gaining some more tropical characteristics. An Air Force
Hurricane Hunter aircraft is scheduled to investigate Alberto later
this morning, and should provide a better assessment of its
intensity and structure.
The initial motion of 015/11 is highly uncertain since the center
of the storm has been re-forming and wobbling around. In fact,
another center re-formation can not be ruled out since Doppler radar
images show a pronounced mid-level circulation to the northeast of
the low-level center. Alberto is expected to turn northward later
today and then northwestward tonight as it moves around the eastern
side of a cutoff mid- to upper-level low over the central Gulf of
Mexico. After Alberto merges with the upper low, a turn back to the
north is forecast by Monday night and Tuesday. The latest model
guidance has shifted notably to the right, and the NHC track
forecast has been adjusted by about 30 n mi in that direction.
The eastward shift necessitates extending the tropical storm warning
along the Gulf coast of Florida.
Even though Alberto has not yet strengthened, slow intensification
seems likely until it reaches the coastline on Monday. The reasons
for intensification consist of diffluence associated with a
negatively tilted upper-level trough, lower shear, and marginally
warm waters in the Gulf of Mexico. However, the intensity models
show a weaker solution this cycle, perhaps because the center may
move inland a little sooner, and no model shows Alberto reaching
hurricane strength. Based on this guidance, the NHC forecast has
been lowered slightly, but it still lies near the high end of the
model predictions. Alberto is likely to complete its transition to
a tropical storm within 24 hours when it moves into an area of light
shear, which should allow the cyclone to develop a deeper warm core
and become more symmetric.
1. Alberto is expected to produce heavy rainfall with a risk of
flooding and flash flooding over western Cuba, the Florida Keys, and
south Florida through the day. The risk for heavy rainfall and
flooding will then spread over many parts of the southeast U.S.
tonight and Monday.
2. Hazardous storm surge is possible along portions of the central
and eastern Gulf Coast beginning later today, including areas well
east of the track of Alberto's center. Residents in the storm surge
watch area are encouraged to follow any guidance given by their
local government officials.
3. Tropical storm conditions are likely within the tropical storm
warning area along the Florida west coast today and within the
warning area along the northern Gulf Coast by tonight.
4. 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 27/0900Z 25.0N 84.2W 35 KT 40 MPH
12H 27/1800Z 26.8N 84.4W 40 KT 45 MPH
24H 28/0600Z 28.6N 85.2W 45 KT 50 MPH...TROPICAL STORM
36H 28/1800Z 30.0N 86.0W 50 KT 60 MPH...TROPICAL STORM
48H 29/0600Z 31.7N 86.3W 35 KT 40 MPH...INLAND
72H 30/0600Z 36.2N 86.8W 20 KT 25 MPH...INLAND
96H 31/0600Z 41.1N 85.1W 15 KT 15 MPH...POST-TROP/REMNT LOW
120H 01/0600Z 45.0N 80.5W 15 KT 15 MPH...POST-TROP/REMNT LOW