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Hurricane Teddy Discussion Number  32
NWS National Hurricane Center Miami FL       AL202020
500 AM AST Sun Sep 20 2020
 
The convective structure of Teddy has degraded substantially since 
the last advisory, with no sign of an eye in conventional satellite 
imagery. The most recent available microwave imagery from last night 
suggested that Teddy still had a very well defined low to mid-level 
inner-core, but this has not translated to the higher levels more 
apparent at night. Intensity estimates have decreased, so the 
initial intensity has been lowered slightly to 100 kt for this 
advisory. An Air Force Reserve Hurricane Hunter aircraft is 
scheduled to investigate the hurricane later this morning and should 
provide more information about its structure and strength.
 
Teddy's evolution for the next few days appears to be a tale of 3 
troughs. Upper-level westerly flow associated with the first 
upper-level trough, affecting the storm now, is the most likely 
reason why the hurricane's structure has degraded and has taken on a 
slightly sheared appearance. Teddy will begin to encounter the 2nd 
trough, a deep frontal system approaching from the west, later today 
and that should cause the hurricane to turn north. This interaction 
should steer the center of Teddy east of Bermuda, but tropical storm 
impacts from either the large hurricane, the frontal system, or both 
are still likely Sunday evening through Monday night. 

All indications are that Teddy will then continue generally 
northward and merge with the frontal system, nearing Nova Scotia as 
an extratropical cyclone early Wednesday. Teddy's maximum winds will 
likely decrease sharply after it becomes post-tropical, as shown by 
all the intensity guidance, but its gale and storm-force wind radii 
will likely increase at the same time. The cyclone should turn 
northeastward as the 3rd trough, another mid-latitude system, 
approaches from the west. Teddy could be absorbed by that feature in 
as soon as 120 h, though this is not explicitly shown in the 
forecast at this time. The spread in the track and intensity 
guidance is quite low and confidence in both aspects of the forecast 
is high. There is a little more uncertainty in the wind radii 
evolution, but it is clear that Teddy will produce strong winds over 
a wide area of the northwest Atlantic during the next couple of 
days.
 
The extent of 12-foot or higher seas associated with Teddy
continues to increase. See the Key Message below regarding swells
caused by the hurricane.
 
 
Key Messages:
 
1. The center of Teddy is forecast to move east of Bermuda late 
Sunday or Monday. Tropical storm conditions are likely on the
island beginning this evening 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 early
next week, where there is an increasing risk of direct impacts from
wind, rain, and storm surge. Residents there should closely monitor
the progress of Teddy and updates to the forecast.
 
3. Large swells produced by Teddy are expected to affect portions
of the Leeward Islands, the Greater Antilles, the Bahamas, Bermuda,
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  20/0900Z 28.0N  62.0W  100 KT 115 MPH
 12H  20/1800Z 28.9N  62.7W   95 KT 110 MPH
 24H  21/0600Z 30.4N  62.9W   90 KT 105 MPH
 36H  21/1800Z 33.3N  62.1W   85 KT 100 MPH
 48H  22/0600Z 37.5N  62.2W   85 KT 100 MPH
 60H  22/1800Z 40.9N  63.2W   75 KT  85 MPH...POST-TROP/EXTRATROP
 72H  23/0600Z 43.8N  62.3W   60 KT  70 MPH...POST-TROP/EXTRATROP
 96H  24/0600Z 51.0N  54.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
120H  25/0600Z 58.5N  41.5W   40 KT  45 MPH...POST-TROP/EXTRATROP
 
$$
Forecaster Zelinsky
 
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