[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 090847
TCDAT1

Hurricane Earl Discussion Number  26
NWS National Hurricane Center Miami FL       AL062022
500 AM AST Fri Sep 09 2022

Radar data from Bermuda and conventional satellite images show that
Earl's structure has improved a bit overnight with the eye becoming
better defined and the overall cloud envelope looking more
symmetric.  An Air Force Reserve Hurricane Hunter aircraft measured
a peak 700-mb flight-level wind of 97 kt and SFMR winds as high as
77 kt, with the central pressure down slightly to 963 mb.  Based on
the typical reduction of the flight-level winds, and accounting for
undersampling of the surface winds, Earl's initial intensity is
raised back to 85 kt.  Reconnaissance and scatterometer data also
indicate that Earl's wind field has continued to expand.

Earl is accelerating toward the north-northeast (030 degrees at 15
kt) ahead of a shortwave trough approaching from the west near the
New England coast.  The hurricane is forecast to turn northeastward
today and continue accelerating to speeds of 25-30 kt within 24
hours.  After that time, however, Earl will merge with the
aforementioned trough, slowing down considerably to speeds of around
5 kt to the southeast of Newfoundland in 60-72 hours.  By days 4 and
5, the system should then move a little bit faster toward the east,
embedded within the mid-latitude westerlies.  The track guidance is
in generally good agreement for much of the 5-day forecast period,
and no significant changes were made to the updated NHC track
forecast.

Earl will remain over warm waters for another 24 hours or so, and
the deep-layer shear should be low to moderate during the next 6 to
12 hours.  As a result, some additional strengthening is anticipated
through tonight, and the NHC intensity forecast is near the IVCN
consensus during that period.  A few models, including SHIPS, LGEM,
and HCCA, still bring Earl to major hurricane strength in 24 hours,
but given that the cyclone will be starting to undergo extratropical
transition by then, that scenario is becoming increasingly unlikely
(although not impossible).  Global model fields indicate that Earl
should complete the transition to a powerful extratropical low by 36
hours and then gradually weaken through the remainder of the
forecast period.  During the extratropical phase, the NHC intensity
forecast is closest to the GFS solution.


KEY MESSAGES:

1.  Tropical storm conditions are expected to diminish on Bermuda
later this morning.

2.  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  09/0900Z 32.7N  62.4W   85 KT 100 MPH
 12H  09/1800Z 35.0N  59.8W   90 KT 105 MPH
 24H  10/0600Z 39.2N  55.5W   95 KT 110 MPH
 36H  10/1800Z 42.7N  52.5W   80 KT  90 MPH...POST-TROP/EXTRATROP
 48H  11/0600Z 44.1N  51.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
 60H  11/1800Z 44.9N  50.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 72H  12/0600Z 45.5N  49.4W   45 KT  50 MPH...POST-TROP/EXTRATROP
 96H  13/0600Z 45.4N  45.5W   35 KT  40 MPH...POST-TROP/EXTRATROP
120H  14/0600Z 46.0N  40.2W   35 KT  40 MPH...POST-TROP/EXTRATROP

$$
Forecaster Berg
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