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Hurricane Teddy Discussion Number  41
NWS National Hurricane Center Miami FL       AL202020
1100 AM AST Tue Sep 22 2020
 
Teddy is in the late stages of extratropical transition.  The 
hurricane has taken on a large comma shape in satellite images, with 
a huge dry-air intrusion aloft near the center and a cold front on 
the western side of the cyclone. While it is tempting to call it an
extratropical now, temperature data from a NOAA Hurricane Hunter 
aircraft indicate that Teddy has maintained a significant warm 
core, and the strongest winds on the southwestern side appear to be 
more related to the cyclone and not the front.  Lastly, deep 
convection is trying to re-develop near the center, another 
indication that the transition is not yet done. Thus Teddy will 
remain a hurricane on this advisory. The initial wind speed is set 
to 90 kt, a blend of the 122-kt flight-level winds, 75-kt SFMR 
values, and global model analyses since much of this large hurricane 
is not being sampled.
 
Teddy should transition into a post-tropical cyclone by the time it 
reaches Nova Scotia and steadily weaken as it moves over the cooler 
waters north of the Gulf Stream.  The cyclone should turn northward 
today and north-northeastward tomorrow ahead of the next trough in 
the mid-latitudes.  This will take Post-Tropical Teddy over Nova 
Scotia and near Newfoundland during the next couple of days, with 
the cyclone likely being absorbed into a larger extratropical 
cyclone west of Greenland in 2-3 days.  There are no significant 
changes to report, except to show a sooner dissipation, which is 
consistent with the latest global models solutions.
 
The hurricane-force and tropical-storm-force winds fields, plus 
12-ft seas area, from Teddy have just about doubled overnight, so it 
is important to note that hazards will extend much farther than 
normal from the center of this hurricane.  The NOAA Hurricane Hunter 
reported hurricane-force surface winds 120 n mi northwest of the 
center, and Canadian buoy 44150 has recently reported 34-ft 
significant wave heights, with the buoy still about 180 n mi from 
the center.
 
Key Messages:
 
1. Teddy is expected to transition to a powerful post-tropical
cyclone as it moves near or over portions of Atlantic Canada
late today through Thursday. The most significant hazard expected
from Teddy is large destructive waves forecast along the southern
coast of Nova Scotia through Wednesday.
 
2. Very 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 are expected to cause
life-threatening surf and rip current conditions.
 
3. Tropical Storm Watches and Warnings are in effect for portions
of Nova Scotia, Prince Edward Island and Newfoundland, and heavy
rainfall across Atlantic Canada is expected with Teddy through
Thursday.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  22/1500Z 39.6N  63.7W   90 KT 105 MPH
 12H  23/0000Z 41.8N  64.1W   75 KT  85 MPH
 24H  23/1200Z 44.8N  62.4W   60 KT  70 MPH...POST-TROP/EXTRATROP
 36H  24/0000Z 48.8N  59.3W   50 KT  60 MPH...POST-TROP/EXTRATROP
 48H  24/1200Z 54.0N  54.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
 60H  25/0000Z...DISSIPATED
 
$$
Forecaster Blake
 
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