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Hurricane Larry Discussion Number  41
NWS National Hurricane Center Miami FL       AL122021
500 PM AST Fri Sep 10 2021
 
Even though Larry is crossing the north wall of the Gulf Stream 
Current, the hurricane remains well organized and has changed little 
during the past several hours.  Satellite images and radar data 
indicate that Larry still has an inner core, though the southern 
side has eroded some.  Large curved bands surround the inner core 
region, with dry slots noted between the core and bands. The initial 
intensity is held at 70 kt based mostly on the ASCAT data from 
earlier today, which showed peak winds of around 65 kt to the east 
of the center.  It should be noted that this intensity value is 
above the Dvorak estimates, which are often not as reliable for high 
latitude storms like Larry.  The earlier ASCAT data confirmed that 
Larry is a large cyclone with hurricane-force and 
tropical-storm-force winds extending outward up to 90 n mi and 220 n 
mi from the center, respectively.  Larry is rapidly approaching 
southeastern Newfoundland, and weather conditions are expected to 
begin to deteriorate there in a few hours.
 
The hurricane continues to accelerate to the north-northeast, and
the latest initial motion estimate is 020/30 kt.  An even faster
north-northeast to northeast motion is expected during the next day
or so as the hurricane moves in the fast flow between a mid- to
upper-level trough over the northeastern U.S./eastern Canada and a
mid-level ridge over the central Atlantic.  This motion should take
Larry across southeastern Newfoundland tonight. Larry is then
expected to merge with a large extratropical low over the Labrador
Sea on Sunday.  The NHC track forecast is largely an update of the
previous one and near the middle of the tightly clustered models.
 
Larry is expected to maintain its intensity through landfall in 
Newfoundland tonight.  However, a combination of land interaction, 
much cooler SSTs, and an increase in shear are expected to promote 
weakening shortly after landfall.  Larry should be fully 
extratropical early Saturday morning when it is forecast to be 
exiting Newfoundland and moving over the cold waters of the 
Labrador Sea. The NHC intensity forecast remains close to the GFS 
model, which often performs well for hurricanes that transition to 
extratropical cyclones.
 
 
Key Messages:
 
1. Larry is forecast to move over portions of southeastern
Newfoundland tonight as it undergoes transition to a
hurricane-force post-tropical cyclone.  Hurricane conditions, a
dangerous storm surge, and heavy rainfall are expected in portions
of southeastern Newfoundland where a Hurricane Warning in effect.
 
2. Large swells generated by Larry will continue to affect the
Bahamas, Bermuda, and the east coast of the United States and
Atlantic Canada through Saturday night. These swells will 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.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  10/2100Z 43.5N  58.2W   70 KT  80 MPH
 12H  11/0600Z 48.6N  53.3W   65 KT  75 MPH...POST-TROP/EXTRATROP
 24H  11/1800Z 54.9N  46.9W   60 KT  70 MPH...POST-TROP/EXTRATROP
 36H  12/0600Z 58.6N  42.4W   60 KT  70 MPH...POST-TROP/EXTRATROP
 48H  12/1800Z...DISSIPATED
 
$$
Forecaster Cangialosi
 
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