[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT42 KNHC 061455
TCDAT2

Hurricane Larry Discussion Number  24
NWS National Hurricane Center Miami FL       AL122021
1100 AM AST Mon Sep 06 2021

Larry currently has an annular structure, with a 60 n-mi diameter
eye and a relatively thick eyewall.  High-resolution visible imagery
shows several meso-vortices rotating within the eye, which is
typically observed in strong hurricanes.  The upper-level outflow
has become better defined over the western portion of the
circulation, indicative of decreased shear in comparison to
yesterday. The advisory intensity is kept at 105 kt, in reasonable
agreement with the latest Dvorak estimates from TAFB and SAB.

Larry has slowed its forward speed a bit, and is now moving
northwestward near 9 kt.  There are no important changes in the
track forecast or reasoning from the previous advisory.  During the
next few days, the hurricane is expected to move around the western
periphery of a subtropical anticyclone over the central Atlantic,
turning northward and northeastward.  At this time, Larry is
forecast to pass east of Bermuda and make its closest approach to
the island on Thursday.  Given Larry's large size, some impacts
could be felt even if the center remains well east of the island as
forecast.  In 3-5 days, the cyclone should accelerate northeastward
ahead of a large mid-tropospheric trough moving through the
northeastern United States.  The official track forecast follows the
latest dynamical model consensus, and remains close to the previous
one.  Since the model guidance is in good agreement, this continues
to be a high-confidence track forecast.

Vertical shear is expected to remain low and the system will
continue to traverse warm SSTs for the next few days.  However, the
presence of dry mid-level air and the broad nature of the
hurricane's inner core will probably mitigate against significant
restrengthening.  Some fluctuations in intensity are possible for
the next 48 hours or so.  In 3-5 days, cooler waters and increasing
shear should cause gradual weakening.  Around the end of the
forecast period, the global models show the system beginning to
merge with a frontal zone near Newfoundland.  The official forecast
is on the high side of the model guidance suite and close to the
latest Decay-SHIPS prediction.

Key Messages:

1. Large swells generated by Larry are affecting the Lesser Antilles
and will spread to portions of the Greater Antilles, the Bahamas,
and Bermuda today through Tuesday.  Significant swells should reach
the east coast of the United States and Atlantic Canada by midweek
and continue affecting these shores through the end of the week.
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 guidance of lifeguards and local officials
this week.

2. Larry is forecast to approach Bermuda during the next few days as
a large and powerful 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  06/1500Z 22.1N  52.9W  105 KT 120 MPH
 12H  07/0000Z 23.1N  54.0W  110 KT 125 MPH
 24H  07/1200Z 24.5N  55.3W  110 KT 125 MPH
 36H  08/0000Z 25.9N  56.6W  105 KT 120 MPH
 48H  08/1200Z 27.5N  58.0W  100 KT 115 MPH
 60H  09/0000Z 29.3N  59.6W  100 KT 115 MPH
 72H  09/1200Z 31.6N  61.2W   95 KT 110 MPH
 96H  10/1200Z 38.6N  60.0W   85 KT 100 MPH
120H  11/1200Z 49.0N  49.0W   70 KT  80 MPH...POST-TROP/EXTRATROP

$$
Forecaster Pasch
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