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Hurricane Teddy Discussion Number  40
NWS National Hurricane Center Miami FL       AL202020
500 AM AST Tue Sep 22 2020
 
Recent satellite imagery shows that the central convection is 
diminishing, with a comma-like cloud pattern developing.  
The current intensity is held at 85 kt based on continuity from the 
earlier aircraft mission.  Another Hurricane Hunter aircraft is 
scheduled to investigate Teddy later today which should provide a 
good estimate of the intensity.  Teddy is moving along the northern 
part of the Gulf Stream and should begin to move into cooler waters 
later today.  Therefore weakening is expected over the next 
couple of days.  However, baroclinic forcing should keep 
the cyclone at or near hurricane strength while it approaches 
Nova Scotia.  The official intensity forecast is above the model 
consensus to qualitatively account for baroclinic effects.  After
72 hours, or sooner, post-tropical Teddy should become absorbed or 
merge with a large extratropical low over the north Atlantic. 

Teddy has accelerated somewhat and is now moving north-northeastward 
near 24 kt.  The hurricane is moving on the eastern side of a 
mid-tropospheric cyclone centered off the northeastern U.S. coast.  
Teddy should continue its north-northwestward motion today and then 
turn north-northeastward as the mid-tropospheric cyclone shifts 
northeastward.  This will take post-tropical Teddy over Nova Scotia 
and near Newfoundland during the next couple of days.  The official 
forecast is close to the corrected dynamical model consensus, or 
HFIP, and similar to the previous NHC track.

The wind field of Teddy should continue to expand today and 
tonight, and the extent of 12-ft seas is also growing.  See the 
Key Message regarding swells due to Teddy.


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, where direct impacts from wind, rain,
and storm surge are expected. Tropical Storm Watches and Warnings
are in effect for portions of Nova Scotia, Prince Edward Island and
Newfoundland.
 
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. Heavy rainfall across Atlantic Canada is expected with Teddy
between today and Thursday after it becomes a strong post-tropical
cyclone.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  22/0900Z 38.4N  62.4W   85 KT 100 MPH
 12H  22/1800Z 40.9N  63.3W   75 KT  85 MPH
 24H  23/0600Z 43.9N  62.9W   65 KT  75 MPH
 36H  23/1800Z 47.5N  60.5W   55 KT  65 MPH...POST-TROP/EXTRATROP
 48H  24/0600Z 52.0N  57.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
 60H  24/1800Z 57.0N  53.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
 72H  25/0600Z 61.0N  52.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
 96H  26/0600Z...DISSIPATED
 
$$
Forecaster Pasch
 
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