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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.
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