[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 080850
TCDAT1

Hurricane Earl Discussion Number  22
NWS National Hurricane Center Miami FL       AL062022
500 AM AST Thu Sep 08 2022

Earl has developed a 20-30 n mi wide eye in infrared satellite
imagery, although a recent Air Force Reserve Hurricane Hunter flight
indicates that the circulation is still tilted toward the east with
height due to continued moderate shear.  That said, this particular
flight measured a peak 700-mb flight-level wind of 97 kt and SFMR
winds as high as 82 kt, while the central pressure dropped to 969
mb.  Recent research on SFMR measurements from the NOAA Hurricane
Research Division and the University of Miami has shown that the
SFMR undersampling for a hurricane of Earl's size is typically
about 10 percent, which would suggest that the maximum winds are up
to around 90 kt.  This estimate also more closely aligns to the
107-kt flight-level wind measured by the NOAA Hurricane Hunter
flight last evening.

The reconnaissance mission found Earl's low-level center to be
located just a bit to the west of the previous forecast track, and
it's still moving toward the north (005 degrees) at 8 kt.  With a
shortwave trough now moving off the New England and Mid-Atlantic
coasts, Earl is expected to turn north-northeastward and begin
accelerating later today, with its center forecast to pass
50-100 n mi to the southeast of Bermuda during the next 12 to 24
hours.  Earl should then turn northeastward in about 36 hours and
reach its fastest forward speed in about 48 hours.  Soon thereafter,
Earl is forecast to become embedded within the aforementioned
trough, which will cause it to slow down considerably and possibly
even meander to the southeast of Newfoundland in 3 to 4 days.  The
new NHC track prediction is shifted a bit westward during the first
48 hours, mainly to account for the recent movement of Earl's
center.  The forecast is a bit north of and slower than the previous
forecast on days 3 through 5, shifted toward the GFS, ECMWF, and
multi-model consensus aids.

Deep-layer shear is expected to decrease to less than 10 kt in just
a few hours.  Along with waters remaining at or above 29 degrees
Celsius for the next 36 hours, the more conducive atmospheric
conditions are expected to cause Earl to strengthen further,
reaching major hurricane intensity later today, and likely peaking
in strength in 36-48 hours.  Earl will start to become involved
with a frontal boundary and deep-layer trough in about 48 hours,
and its transition to a powerful extratropical cyclone is now
expected to be complete to the southeast of Newfoundland by 60
hours.  The extratropical low is expected to weaken rather quickly,
with its winds falling below hurricane force between days 3 and 4.
The NHC intensity prediction closely follows the IVCN and HCCA
consensus aids for much of the 5-day forecast period.


KEY MESSAGES:

1.  Although Earl's center is forecast to pass southeast of Bermuda,
tropical-storm-force winds are expected on the island this
afternoon through early Friday morning.  Hurricane-force winds are
possible on Bermuda this evening or tonight if Earl's track shifts
farther west than is currently forecast.

2.  Swells generated by Earl are building near Bermuda and are
expected to reach the U.S. East Coast later today and tonight.
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  08/0900Z 28.2N  65.4W   90 KT 105 MPH
 12H  08/1800Z 29.6N  64.8W  100 KT 115 MPH
 24H  09/0600Z 32.0N  63.0W  110 KT 125 MPH
 36H  09/1800Z 35.1N  59.7W  115 KT 130 MPH
 48H  10/0600Z 39.1N  55.5W  115 KT 130 MPH
 60H  10/1800Z 42.4N  51.7W   95 KT 110 MPH...POST-TROP/EXTRATROP
 72H  11/0600Z 44.3N  49.0W   70 KT  80 MPH...POST-TROP/EXTRATROP
 96H  12/0600Z 45.4N  47.1W   45 KT  50 MPH...POST-TROP/EXTRATROP
120H  13/0600Z 46.7N  41.7W   40 KT  45 MPH...POST-TROP/EXTRATROP

$$
Forecaster Berg
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