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Subtropical Storm Alberto Discussion Number 7...Corrected
NWS National Hurricane Center Miami FL AL012018
1100 PM EDT Sat May 26 2018
Corrected typo in key message 3
During the past few hours, a burst of convection has formed just
north of the low-level center of Alberto, which has caused the
center to reform somewhat to the northeast of the previous position.
Despite an overall increase in organization, however, reports from
an Air Force Reserve Hurricane Hunter aircraft are at best
ambiguous on whether the storm has strengthened. The maximum
flight-level winds at 925 mb were 45 kt, which would support 30-35
kt at the surface. The maximum SFMR winds outside of the
convective burst were 35-37 kt, but since these were higher than
the associated flight-level winds it is unclear how reliable they
were. In the convection, there were SFMR winds up to near 60 kt
which may be due to downbursts and thus are unrepresentative of the
strength of the storm. Finally, the central pressure has not fallen
since the previous mission and is near 1001 mb. The initial
intensity will remain 35 kt, but this could be conservative.
In the next 24 h, Alberto should intensify as a subtropical storm
due to the influence of a negative-tilt upper-level trough just
west of the cyclone. After that time, the trough is forecast to
become a cutoff upper-level low, with the center of Alberto near or
just north of the low in an area of lighter shear. This evolution
should allow the cyclone to develop a deeper warm core and become
more symmetric, and this in turn should lead to Alberto
transitioning from a subtropical to a tropical storm by 36-48 h.
There is little intensity guidance that makes Alberto a hurricane
before landfall, so the new intensity forecast keeps the same 55 kt
peak and landfall intensities as the previous forecast. After
landfall on the northern Gulf Coast, Alberto should steadily weaken
over land through the remainder of the forecast period.
For the next 12 h or so, Alberto should move generally northward,
although some additional eastward reformation of the center remains
possible. From 12-48 h, the cyclone should move
north-northwestward as it merges with the upper-level low. This
should be followed by a northward motion across the southeastern
United States from 48-96 h and a subsequent recurvature into the
westerlies. The forecast guidance is in good agreement, and the
new forecast track is nudged just a little to the east of the
previous track. On the current forecast track, Alberto would make
landfall near the 48 h point.
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. Heavy rainfall and flooding
potential will expand to include much of the central U.S. Gulf Coast
region and portions of the southeastern United States beginning
Sunday and will continue into next week.
2. Hazardous storm surge is possible along portions of the central
and eastern Gulf Coast beginning on Sunday, 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 on Sunday and within the
warning area along the northern Gulf Coast beginning Sunday night.
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 27/0300Z 23.9N 84.6W 35 KT 40 MPH
12H 27/1200Z 25.9N 84.6W 45 KT 50 MPH
24H 28/0000Z 27.7N 85.6W 50 KT 60 MPH
36H 28/1200Z 28.9N 86.4W 55 KT 65 MPH...TROPICAL STORM
48H 29/0000Z 30.4N 86.8W 55 KT 65 MPH...TROPICAL STORM
72H 30/0000Z 34.5N 87.6W 25 KT 30 MPH...INLAND
96H 31/0000Z 39.0N 86.5W 20 KT 25 MPH...INLAND
120H 01/0000Z 42.5N 82.0W 15 KT 15 MPH...POST-TROPICAL