[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT41 KNHC 091435
TCDAT1

Hurricane Earl Discussion Number  27
NWS National Hurricane Center Miami FL       AL062022
1100 AM AST Fri Sep 09 2022

During the past six hours, Earl's satellite appearance has
oscillated between periods of gaining symmetry and becoming more
ragged, with the latter winning out right now.  In fact, Earl's
previously clear eye has become partially obscured by clouds during
the last hour or two. Satellite-based intensity estimates range from
70-100 kt, but since those estimates generally haven't changed much
since the last advisory, the hurricane's intensity is held at 85 kt
for now.

Whether Earl's recent satellite degradation is another temporary
hiccup or the start of a weakening trend as it undergoes
extratropical transition over the next 24 h isn't yet clear, but
either way the intensity guidance is now in good agreement that
little or no intensification is expected going forward. Dynamical
models including the GFS and ECMWF are also in very good agreement
that Earl will become post-tropical by Saturday afternoon or
evening. This transition should coincide with the cyclone's maximum
winds to decreasing sharply while the extent of its tropical storm
or gale-force winds expands. The NHC intensity forecast shows a
slightly faster rate of weakening than the previous advisory, but is
still on the high end of the narrow intensity guidance envelope
through 72 h. The official intensity forecast is based heavily on
the consensus after that.

Earl continues to accelerate toward the northeast ahead of an
approaching shortwave trough off the New England and Atlantic Canada
coasts. This should cause Earl to accelerate further today and
tonight before it merges with the trough and slows to a relative
crawl southeast of Newfoundland as a post-tropical cyclone in about
48 h. Around day 4-5, the broader mid-latitude system should move
faster eastward, bringing extratropical Earl with it. Only minor
adjustments were made to the NHC track forecast.

KEY MESSAGES:

1.  Swells generated by Earl are affecting Bermuda and the U.S. East
Coast and are expected to reach Nova Scotia and Newfoundland tonight
and on Saturday.  These swells are likely to cause life-threatening
surf and rip current conditions through the weekend.  Please consult
products from your local weather office.


FORECAST POSITIONS AND MAX WINDS

INIT  09/1500Z 34.2N  61.0W   85 KT 100 MPH
 12H  10/0000Z 37.0N  57.9W   90 KT 105 MPH
 24H  10/1200Z 41.0N  54.1W   85 KT 100 MPH
 36H  11/0000Z 43.5N  52.0W   70 KT  80 MPH...POST-TROP/EXTRATROP
 48H  11/1200Z 44.4N  51.0W   55 KT  65 MPH...POST-TROP/EXTRATROP
 60H  12/0000Z 45.1N  50.2W   45 KT  50 MPH...POST-TROP/EXTRATROP
 72H  12/1200Z 45.5N  49.4W   40 KT  45 MPH...POST-TROP/EXTRATROP
 96H  13/1200Z 45.5N  45.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
120H  14/1200Z 46.0N  40.5W   35 KT  40 MPH...POST-TROP/EXTRATROP

$$
Forecaster D. Zelinsky
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