Hurricane Teddy Forecast Discussion


000
WTNT45 KNHC 190259
TCDAT5

Hurricane Teddy Discussion Number  27
NWS National Hurricane Center Miami FL       AL202020
1100 PM AST Fri Sep 18 2020

Teddy continues to have an impressive appearance on satellite 
images with a fairly symmetrical Central Dense Overcast, although 
recent images show some warming of the cloud tops over the 
southeastern part of the circulation.  Upper-level outflow is 
well-defined over the northern semicircle of the hurricane and 
not as strong to the south.  Earlier microwave images showed a 
concentric eyewall structure and it appears that the hurricane has 
re-intensified slightly over the past several hours.  The current 
intensity estimate is set at 115 kt which is a blend of subjective 
and objective Dvorak estimates.  Some additional fluctuations in 
strength as a result of eyewall replacements could occur through 
Saturday.  On Sunday and beyond, a less conducive oceanic and 
atmospheric environment should lead to slow weakening.  However, 
Teddy should remain a powerful hurricane for the next several days. 
The numerical guidance shows that the circulation will become even 
larger during the forecast period due to Teddy combined with a 
high pressure area coming behind a cold front over the eastern 
United States.  Teddy is expected to make the transition to an 
extratropical cyclone when  it moves into Atlantic Canada.   

The hurricane continues its northwestward trek and is moving around 
325/11 kt.  Teddy should move around the western side of a 
subtropical high pressure system for the next day or so.  Then, the 
cyclone should turn northward with an increase in forward speed as 
it approaches a strong mid-latitude trough cutting off into a low 
as it moves off the northeast U.S. coast in 2-3 days.  The track 
of the system could bend a bit the left as it interacts with the 
trough/low while approaching Nova Scotia.  Around the end of the 
forecast period, the post-tropical cyclone should turn 
northeastward as it moves along the eastern side of a mid-level 
trough.  The official track forecast is close to the corrected model 
consensus.

Teddy is producing seas to 48 feet and an extensive area of large 
waves and swells which are impacting much of the western Atlantic 
basin.  See the Key Messages below.


Key Messages:

1. While the center of Teddy is forecast to move east of Bermuda
late Sunday or Monday, there is still a risk of strong winds, storm
surge, and heavy rainfall on the island, and a Tropical Storm Watch
is in effect.

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 through the
weekend.

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  19/0300Z 24.0N  57.4W  115 KT 130 MPH
 12H  19/1200Z 25.5N  58.6W  115 KT 130 MPH
 24H  20/0000Z 27.3N  60.4W  110 KT 125 MPH
 36H  20/1200Z 29.0N  61.8W  105 KT 120 MPH
 48H  21/0000Z 30.8N  62.3W  100 KT 115 MPH
 60H  21/1200Z 33.5N  61.4W   95 KT 110 MPH
 72H  22/0000Z 37.7N  61.1W   85 KT 100 MPH
 96H  23/0000Z 45.5N  62.5W   70 KT  80 MPH...POST-TROP/EXTRATROP
120H  24/0000Z 50.5N  56.0W   45 KT  50 MPH...POST-TROP/EXTRATROP

$$
Forecaster Pasch

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