Hurricane Teddy Forecast Discussion


377 
WTNT45 KNHC 220248
TCDAT5

Hurricane Teddy Discussion Number  39
NWS National Hurricane Center Miami FL       AL202020
1100 PM AST Mon Sep 21 2020

Air Force Reserve hurricane hunter found Teddy a little stronger
this evening.  Flight level peak wind was 111 kt in the east
quadrant and the highest observed SFMR wind was 69 kt.  A blend of 
these data yields an initial intensity of 85 kt for this advisory.

Teddy is accelerating toward the north in response to a mid- to
upper tropospheric mid-latitude trough approaching from the
northwest.  Dynamic forcing produced by the aforementioned
baroclinic system and warm (27-28C) waters associated with the Gulf
Stream could induce a short period of strengthening during the
next few hours, or so.  Through the remaining portion of the
forecast period, Teddy will traverse cooler oceanic temperatures
north of the Gulf Stream and lose its baroclinic support inducing a
gradual weakening trend as the post-tropical cyclone quickly moves
over eastern Nova Scotia, the Gulf of St. Lawrence and Newfoundland.
After that time, Teddy should become absorbed by a larger 
non-tropical, high latitude low pressure system.  There still 
remains much uncertainty as to whether or not Teddy will complete 
its extratropical transition prior to reaching Nova Scotia.  The 
global models show the cyclone merged or embedded in the baroclinic 
zone, but the associated simulated infrared presentation shows 
Teddy maintaining a rather small warm, inner core.  Regardless of 
it classification during that time, high winds, heavy rain, storm 
surge and destructive waves are still predicted for the south coast 
of Nova Scotia.

Teddy's horizontal wind profile is forecast to nearly double during
the next couple of days as it moves northward and interacts with
the aforementioned baroclinic system.  Gale-force winds are likely
along portions of the near shore waters of the northeast United
States.  The forecast wind radii at the 24 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.

Please see products from your local office for more
information about marine hazards, including extremely dangerous rip
currents expected over much of the western Atlantic beaches.

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 Tuesday 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 Tuesday and Thursday after it becomes a strong post-tropical 
cyclone. 

FORECAST POSITIONS AND MAX WINDS

INIT  22/0300Z 35.6N  61.5W   85 KT 100 MPH
 12H  22/1200Z 38.4N  62.6W   85 KT 100 MPH
 24H  23/0000Z 41.1N  63.1W   70 KT  80 MPH
 36H  23/1200Z 44.6N  61.5W   60 KT  70 MPH
 48H  24/0000Z 49.0N  58.7W   50 KT  60 MPH...POST-TROP/EXTRATROP
 60H  24/1200Z 52.8N  54.8W   45 KT  50 MPH...POST-TROP/EXTRATROP
 72H  25/0000Z 58.1N  51.4W   40 KT  45 MPH...POST-TROP/EXTRATROP
 96H  26/0000Z...DISSIPATED

$$
Forecaster Roberts


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