Tropical Storm LARRY Advisory dom, 05-09

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Hurricane Larry Discussion Number  19
NWS National Hurricane Center Miami FL       AL122021
500 AM AST Sun Sep 05 2021

Larry remains a powerful hurricane this morning. The system has a
warm, well-defined eye with a large diameter of around 40 n mi.
Larry's central dense overcast has become more symmetric overnight,
although the upper-level outflow is still somewhat restricted on the
southwestern side of the hurricane. This is likely an indication of
some vertical wind shear impinging on the cyclone. However, recent
AMSR2 microwave data indicate that the vortex is still well-aligned
vertically, with a pronounced eyewall that slopes outward with
height. The initial intensity is held at 105 kt for this advisory
based on consensus T5.5/102 kt Dvorak classifications from TAFB and
SAB, and a recent UW-CIMSS ADT estimate of 105 kt.

The initial motion of Larry is northwestward, or 305/12 kt. Larry is
expected to continue moving northwestward for the next several days
around the southwestern periphery of a mid-level ridge over the
central Atlantic. By Thursday, the cyclone is forecast to accelerate
northward ahead of a deep-layer trough that will move off the east
coast of the United States later this week. The latest track
guidance is very tightly clustered, and the official NHC forecast is
similar to the previous one and lies near the multi-model consensus
aids. Confidence remains high in Larry's track forecast given the
excellent model agreement. The hurricane is still expected to make
its closest approach to Bermuda at days 4 and 5, but it remains too
early to pinpoint how close it will come to the island. Even if the
center passes east of Bermuda as forecast, it could still be large
enough to produce some impacts on the island.

Over the next few days, some fluctuations in Larry's intensity are
possible. The oceanic heat content along the forecast track is
certainly sufficient for some intensification. However, vertical
wind shear associated with an upper-level trough/low to the west of
Larry may inhibit strengthening at times during the next couple of
days, especially if the stronger shear values in the ECMWF-based
SHIPS guidance are realized. Given Larry's large eye size, it does
not appear as if the cyclone is poised to significantly intensify.
The official NHC intensity forecast shows slight strengthening in
the near-term, but then levels off the intensity through 48 h. The
NHC forecast keeps Larry at major hurricane intensity through day 4,
as the environment appears favorable enough between 48-96 h for
Larry to maintain its organization, even as the cyclone gains
latitude. Overall, this forecast lies on the high end of the
intensity guidance, above the HFIP corrected consensus approach
(HCCA) and the other multi-model consensus aids.


Key Messages:

1. Large swells generated by Larry are expected to reach the Lesser
Antilles today and will spread to portions of the Greater Antilles,
the Bahamas, and Bermuda on Monday and Tuesday.  Significant swells
will likely reach the east coast of the United States and Atlantic
Canada by midweek.  These swells will likely cause life-threatening
surf and rip current conditions, and beachgoers and other interests
along these coasts are urged to follow the advice of lifeguards and
local officials this week.

2. Larry is forecast to approach Bermuda during the next several
days, possibly as a major hurricane, bringing a risk of strong
winds, heavy rainfall, and coastal flooding to the island by the
middle of this week.  While it is too soon to determine the
magnitude of these hazards and potential impacts on Bermuda,
interests there should closely monitor the latest forecast updates
during the next several days.


FORECAST POSITIONS AND MAX WINDS

INIT  05/0900Z 18.8N  49.0W  105 KT 120 MPH
 12H  05/1800Z 19.9N  50.4W  110 KT 125 MPH
 24H  06/0600Z 21.2N  52.1W  110 KT 125 MPH
 36H  06/1800Z 22.4N  53.6W  110 KT 125 MPH
 48H  07/0600Z 23.6N  55.0W  110 KT 125 MPH
 60H  07/1800Z 25.0N  56.4W  105 KT 120 MPH
 72H  08/0600Z 26.5N  57.8W  105 KT 120 MPH
 96H  09/0600Z 30.4N  60.8W  100 KT 115 MPH
120H  10/0600Z 36.5N  61.0W   90 KT 105 MPH

$$
Forecaster Reinhart