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Hurricane Larry Discussion Number  28
NWS National Hurricane Center Miami FL       AL122021
1100 AM AST Tue Sep 07 2021
 
An Air Force Reserve Unit Hurricane Hunter aircraft investigated
Larry a little while ago and found that the hurricane has weakened
somewhat.  The central pressure has risen to 967 mb, and the eyewall
is becoming less well defined.  Satellite imagery shows that the eye
is still evident but the deep convection has has decreased in
coverage and intensity.  Using a blend of flight-level and
SFMR-observed surface winds from the aircraft gives a current
intensity estimate of 100 kt, although this may be generous.
 
The hurricane continues to move northwestward, or 315/8 kt.  Larry
is forecast to move around the western periphery of a subtropical
anticyclone during the next couple of days.  By 72 hours, the
system should begin to accelerate northeastward on the eastern side
of a mid-tropospheric trough moving through the northeastern United
States.  Thereafter, Larry should be well-embedded in the
higher-latitude southwesterly flow, pass near Newfoundland and move
into the far North Atlantic as an extratropical cyclone.  The
official track forecast is essentially the same as the previous one
and in very close agreement with the latest NOAA corrected
consensus and Florida State University (FSU) Superensemble tracks.
 
Larry is in a low-shear environment with fairly well-defined
upper-level outflow.  However dry mid-level air and possible
upwelling of cooler waters beneath the slow-moving circulation
appear to be at least partially responsible for weakening.  Since
the environment does not appear to be very hostile for the next
couple of days, only slow weakening is anticipated.  The official
intensity forecast for the next 48-72 hours lies below the
statistical dynamical Decay-SHIPS guidance and above the coupled-
HWRF dynamical model prediction.  By 96 hours, the FSU cyclone
phase analysis indicates that Larry will have undergone an
extratropical transition, and this is also shown in the official
forecast.
 
Larry is expected to pass east of Bermuda on Thursday as a large
hurricane.  Given the expansive size of Larry's wind field and
forecast uncertainties, a Tropical Storm Watch has been issued
for the island.
 
Key Messages:
 
1. Large swells generated by Larry will continue to affect the
Lesser Antilles, portions of the Greater Antilles, and the Bahamas
through midweek.  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. The center of Larry is forecast to pass east of Bermuda on 
Thursday, but given Larry's large size, tropical storm conditions 
are possible there Thursday, along with a risk of heavy rainfall 
and coastal flooding.  A Tropical Storm Watch is in effect for 
Bermuda and interests there should closely monitor the latest 
forecast updates.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  07/1500Z 24.4N  55.6W  100 KT 115 MPH
 12H  08/0000Z 25.6N  56.6W   95 KT 110 MPH
 24H  08/1200Z 27.3N  58.1W   90 KT 105 MPH
 36H  09/0000Z 29.3N  59.9W   90 KT 105 MPH
 48H  09/1200Z 31.8N  61.3W   90 KT 105 MPH
 60H  10/0000Z 34.9N  61.8W   85 KT 100 MPH
 72H  10/1200Z 39.0N  60.0W   80 KT  90 MPH
 96H  11/1200Z 50.0N  50.0W   65 KT  75 MPH...POST-TROP/EXTRATROP
120H  12/1200Z 58.0N  42.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 
$$
Forecaster Pasch
 
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