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Hurricane Teddy Discussion Number  35
NWS National Hurricane Center Miami FL       AL202020
1100 PM AST Sun Sep 20 2020
 
Teddy's satellite presentation has changed little during the 
past several hours albeit some warming of the eye.  The 
53rd Air Force Reserve hurricane hunters recorded a central 
pressure this evening of 963 mb, unchanged from the previous 
mission, and the Dvorak subjective intensity estimates haven't 
changed either.  Therefore, the initial intensity is held at 90 kt 
for this advisory.  
 
There is a chance, within the next 24 hours, that Teddy could 
strengthen a bit due to dynamic forcing as a result of the 
approaching baroclinic zone moving off of the northeast coast of 
the United States.  In Fact, the HCCA intensity model shows a peak 
of 95 kt at the 24 hour period.  By Tuesday afternoon, however, 
increasing southwesterly shear associated with the rapidly 
approaching mid-latitude major shortwave trough, from the northwest, 
should induce weakening.  Because Teddy is a very large and strong 
tropical cyclone, only gradual weakening is predicted.  By mid 
period, the large-scale models agree that Teddy will merge with the 
aforementioned trough and associated frontal zone and complete its 
extratropical cyclone transition south of Nova Scotia Tuesday 
evening.  Teddy is still forecast to be a very large and powerful 
extratropical cyclone as it approaches, Nova Scotia at that time.  
Wind, rain, surf and storm surge hazards are expected to spread over 
an extensive portion of Atlantic Canada mid-week.
 
The forecast wind radii at the 36 hour period and beyond, are based
on the RVCN Wind Radii Consensus model that consists of a
bias-corrected average of the global and regional models.
 
The initial motion is estimated to be north-northwestward, or 5 kt.
The hurricane is likely to turn northward Monday morning and 
continue in this general motion through Wednesday morning.  Around 
the 60 hour period, a turn north-northeastward is forecast ahead of 
yet another mid-latitude pulse moving into eastern Canada. No 
significant adjustments were made to the NHC track forecast and 
it lies in between the surprisingly tightly clustered model 
guidance.

Extremely dangerous surf conditions with 20-ft waves have been
reported on the south shore of Bermuda, and officials are
encouraging residents to avoid going into or near the water.
 
Key Messages:
 
1. The center of Teddy is forecast to move east of Bermuda on
Monday. Tropical storm conditions are likely on the island beginning
overnight and could continue into Monday evening.
 
2. Teddy is expected to transition to a powerful post-tropical
cyclone as it moves near or over portions of Atlantic Canada
late Tuesday through Thursday, where there is an increasing risk of
direct impacts from wind, rain, and storm surge. A Tropical Storm
Watch is in effect for portions of Nova Scotia, and heavy 
rainfall across Atlantic Canada is expected with Teddy between 
Tuesday and Thursday after it becomes a strong post-tropical 
cyclone.

3. Large swells produced by Teddy are expected to affect portions of
Bermuda, the Leeward Islands, the Greater Antilles, the Bahamas, the
east coast of the United States, and Atlantic Canada during the next
few days. These swells could cause life-threatening surf and rip
current conditions.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  21/0300Z 29.4N  63.6W   90 KT 105 MPH
 12H  21/1200Z 30.9N  63.5W   90 KT 105 MPH
 24H  22/0000Z 34.8N  62.9W   95 KT 110 MPH
 36H  22/1200Z 38.5N  63.8W   90 KT 105 MPH
 48H  23/0000Z 41.3N  64.2W   80 KT  90 MPH...POST-TROP/EXTRATROP
 60H  23/1200Z 44.5N  62.8W   65 KT  75 MPH...POST-TROP/INLAND
 72H  24/0000Z 48.6N  59.9W   50 KT  60 MPH...POST-TROP/EXTRATROP
 96H  25/0000Z 57.4N  47.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
120H  26/0000Z...ABSORBED BY A LARGER LOW
 
$$
Forecaster Roberts
 
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