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Hurricane Larry Discussion Number  38
NWS National Hurricane Center Miami FL       AL122021
1100 PM AST Thu Sep 09 2021

There is not much new to report in the satellite structure with 
Larry this evening. The hurricane consists of a small core region of 
cold convective cloud tops near and just north of the center with a 
much larger concentric band of more moderate convective activity 
encircling the smaller core. Radar from Bermuda also shows this 
structure well even as the hurricane pulls away from the island. The 
most recent subjective Dvorak satellite intensity estimates from SAB 
and TAFB were unchanged from this afternoon, and the initial 
intensity will remain at 80 kt for this advisory.

Larry is now moving to the north and beginning to accelerate at 
360/20 kt. The track guidance remains in good agreement that Larry 
should soon turn to the northeast and continue accelerating quickly 
ahead of a large mid-latitude trough. On the current track, Larry 
should pass near or over southeastern Newfoundland tomorrow night or 
Saturday morning, becoming post-tropical shortly after it passes by. 
The post-tropical cyclone Larry should continue to move rapidly to 
the northeast until it is absorbed by the aforementioned 
mid-latitude trough after 48 hours. The official track forecast 
again lies close to the various consensus model predictions, and is 
just a touch faster than the previous forecast.

Larry has another 12 hours or so over warm Gulf Stream waters, and 
most of the guidance is in agreement that the hurricane should 
maintain its intensity in the short-term. However, more gradual 
weakening should begin thereafter once Larry moves over much cooler 
waters. Unfortunately, there is not much time for Larry to weaken 
before the hurricane impacts Newfoundland, and it also is possible 
the rapidly approaching mid-latitude trough will provide some 
baroclinic forcing that could expand the wind field of the 
hurricane further. The NHC intensity forecast remain close to the 
latest HCCA guidance which is quite similar to the previous 
forecast. After 24 hours, the latest forecast GFS and ECMWF 
simulated IR brightness temperature suggest that Larry's convection 
should quickly shear off after passing by Newfoundland, with the 
hurricane becoming a powerful post-tropical cyclone by 36 hours. 
Both of these models now also suggest the post-tropical cyclone 
will quickly be stretched and then absorbed as its captured by an 
even larger extratropical cyclone produced by the upstream 
trough after 48 hours.
 
Key Messages:
 
1. Larry is forecast to move near or over portions of southeastern
Newfoundland Friday night or early Saturday morning as it undergoes
transition to a hurricane-force post-tropical cyclone.  Hurricane
conditions and dangerous storm surge are expected in portions of
southeastern Newfoundland where a Hurricane Warning in effect.
 
2. 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 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  10/0300Z 35.5N  62.3W   80 KT  90 MPH
 12H  10/1200Z 39.0N  60.9W   80 KT  90 MPH
 24H  11/0000Z 45.1N  56.1W   75 KT  85 MPH
 36H  11/1200Z 52.0N  49.3W   65 KT  75 MPH...POST-TROP/EXTRATROP
 48H  12/0000Z 58.1N  44.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
 60H  12/1200Z...DISSIPATED
 
$$
Forecaster Papin
 
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