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Hurricane Larry Discussion Number  35
NWS National Hurricane Center Miami FL       AL122021
500 AM AST Thu Sep 09 2021
 
This morning's conventional satellite presentation appears to
indicate a more banding eye feature rather than a previously noted
irregular-type eye. A timely Advanced Technology Microwave
Sounder (ATMS) image and an AMSR2 lower frequency pass, however, 
clearly shows the majority of the eyewall intact.  The primary 
curved band wrapping around the west semicircle consists of -78 
Celsius cloud tops.  The western portion of the eyewall is now 
discernible on the Bermuda Weather Service Radar.  The initial 
intensity is held at possibly generous 85 kt for this advisory and 
is based on a compromise of the subjective and objective satellite 
intensity estimates.  A 53rd Air Force Reserve Unit reconnaissance 
mission is scheduled for this morning and will provide new 
information on Larry's intensity.
 
The 0000 UTC GFS global model sounding revealed 15 to 20 kt of
southwesterly effective shear impinging on the western
half of the cyclone while the UW-CIMSS shear analysis showed 20-25 
kt of bulk shear in the same area.  This, along with a 
significantly higher statically stable surrounding environment 
(about 55 percent RH), has disrupted the inner core and more than 
likely created a SW to NW tilt with height.  Larry is expected to 
change little in strength during the next 12 to 24 hours, then 
gradually weaken as the cyclone traverses sharply decreasing cooler 
water north of the gulf stream while the southwesterly shear 
increases significantly.  The dynamic forcing, however, associated 
with a mid-latitude major shortwave trough near Atlantic Canada 
should aid in maintaining Larry as a hurricane while it passes near 
or over Newfoundland.  Afterwards, Larry is expected to transition 
into a large extratropical cyclone, as indicated by the FSU Cyclone 
Phase Diagram.  By early next week, Larry is expected to be 
absorbed by a larger extratropical low.
 
The initial motion is estimated to be north-northwestward, or 
330/14 kt.  The track philosophy remains unchanged.  Larry is 
expected to move around the western periphery of a subtropical high 
pressure system anchored over the central Atlantic.  The hurricane 
should make its closest approach to the east of Bermuda later today 
while slowly turning north-northwestward and northward. Through the 
remaining portion of the forecast, Larry should  accelerate 
generally northeastward in response to the aforementioned 
mid-latitude trough and move near or over southeastern Newfoundland 
Friday night.  The NHC forecast has been nudged a bit to the left 
of the previous advisory and is close to the various multi-model 
consensus aids.
 
The wind radii were decreased slightly in all quadrants based on
earlier METOP A and B scatterometer passes.

Key Messages:
 
1. Large swells generated by Larry will continue to affect the
Leeward Islands, portions of the Greater Antilles, the Bahamas,
Bermuda, and the east coast of the United States and Atlantic
Canada 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 later 
today, Tropical storm conditions are expected today, along with a 
risk of coastal flooding.  A Tropical Storm Warning is in effect for 
Bermuda, and interests there should closely monitor the latest 
forecast updates.
 
3. Larry is forecast to move near or over portions of southeastern
Newfoundland Friday night, early Saturday morning as it undergoes 
transition to a hurricane-force post-tropical cyclone.  Hurricane 
and Tropical Storm Watches are in effect for southeastern 
Newfoundland.  There is an increasing risk of impacts from high 
winds, rainfall, and storm surge in portions of Newfoundland, and 
interests there should monitor updates to the forecast.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/0900Z 30.9N  61.1W   85 KT 100 MPH
 12H  09/1800Z 32.9N  62.1W   85 KT 100 MPH
 24H  10/0600Z 36.7N  62.0W   85 KT 100 MPH
 36H  10/1800Z 41.8N  59.0W   80 KT  90 MPH
 48H  11/0600Z 47.9N  52.5W   70 KT  80 MPH
 60H  11/1800Z 54.1N  45.9W   60 KT  70 MPH...POST-TROP/EXTRATROP
 72H  12/0600Z 59.2N  41.2W   60 KT  70 MPH...POST-TROP/EXTRATROP
 96H  13/0600Z...ABSORBED
 
$$
Forecaster Roberts
 
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