Hurricane Teddy Discussion Number  29
NWS National Hurricane Center Miami FL       AL202020
1100 AM AST Sat Sep 19 2020

The overall appearance of Teddy has degraded slightly since early 
this morning, with the eye no longer readily apparent in satellite 
imagery. However, microwave data a few hours ago showed that a well- 
defined outer eyewall exists with a decaying partial inner eyewall. 
This indicates that an eyewall replacement cycle is just about 
complete. The objective and subjective satellite intensity estimates 
generally agree on an intensity of 98-102 kt, but out of respect for 
the completing eyewall replacement cycle the initial intensity is 
set to a slightly more generous 105 kt. 

Teddy will be moving over slightly cooler waters caused by upwelling 
from Paulette over the next day or so and this should cause the 
hurricane to slowly weaken. However, in about 36 h the cyclone's 
wind field is forecast to begin expanding as it interacts with an 
approaching frontal system. Around 48-60 h, vertical wind shear is 
expected to dramatically increase as Teddy becomes embedded in the 
flow around a sharp mid-latitude upper-level trough. The interaction 
of the cyclone with both the front and trough should cause Teddy to 
begin an extratropical transition, with the post-tropical cyclone 
quickly weakening once the transition is complete. The SHIPS 
guidance and global model simulated satellite imagery tend to agree 
that the extratropical transition should be completed just after 72 
h. The latest NHC intensity forecast was nudged downward slightly 
mainly due to the change in the initial intensity, and is close to 
the HFIP corrected consensus HCCA. 

The hurricane continues its northwestward movement, now at 12 kt. 
The track forecast for Teddy remains essentially unchanged and is in 
the middle of tightly clustered guidance. Teddy is expected to turn 
northward to north-northeastward Sunday morning as it approaches a 
frontal system over the western Atlantic. This pattern should steer 
the hurricane east of Bermuda, though the hurricane's large wind 
field means that the island will still likely experience tropical 
storm conditions beginning by Sunday evening and continuing through 
much of Monday. A slight turn to the north then perhaps the north- 
northwest should occur Monday night into Tuesday as Teddy pivots 
around the upper trough. By Tuesday night, the cyclone is forecast 
to turn northeastward as the upper trough to its southwest begins to 
lift into the higher latitudes. 

Teddy is producing 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, tropical storm conditions are likely on the 
island beginning Sunday afternoon or 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  19/1500Z 26.0N  59.0W  105 KT 120 MPH
12H  20/0000Z 27.3N  60.4W  100 KT 115 MPH
24H  20/1200Z 28.8N  61.7W   95 KT 110 MPH
36H  21/0000Z 30.4N  62.2W   90 KT 105 MPH
48H  21/1200Z 33.1N  61.6W   90 KT 105 MPH
60H  22/0000Z 37.1N  61.2W   90 KT 105 MPH
72H  22/1200Z 40.8N  61.8W   80 KT  90 MPH
96H  23/1200Z 47.0N  59.8W   55 KT  65 MPH...POST-TROP/EXTRATROP
120H  24/1200Z 52.9N  51.1W   40 KT  45 MPH...POST-TROP/EXTRATROP

$$
Forecaster Latto