Tropical Storm TEDDY Advisory di, 22-09

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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