[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 070852
TCDAT1

Hurricane Earl Discussion Number  18
NWS National Hurricane Center Miami FL       AL062022
500 AM AST Wed Sep 07 2022

Strong westerly shear (analyzed to be around 30 kt) continues to
affect Earl, with the hurricane exhibiting an asymmetric convective
structure in infrared satellite imagery.  A recent Air Force Reserve
Hurricane Hunter aircraft reported that the central pressure has
fallen to 981 mb, however there's been no apparent change in the
maximum winds and the eyewall is open to the south and southeast.
The plane measured a peak 700-mb flight-level wind of 78 kt and SFMR
winds as high as 71 kt; therefore the maximum sustained winds are
still estimated to be 70 kt.

Earl has been moving slowly just west of due north, or 355/5 kt,
while sandwiched between a mid-level ridge over the central
Atlantic and high pressure over Florida.  A trough over the eastern
United States is expected to move offshore during the next couple
of days, causing Earl to turn northeastward and accelerate through
day 3.  The track guidance is tightly clustered during the first 3
days of the forecast, although many of the models have trended a
little slower during the northeastward turn.  No cross-track
adjustments to the NHC forecast were needed during that period.
There has been a marked shift and increase in spread among the
track models on days 4 and 5, however, with the GFS, ECMWF, and
COAMPS-TC showing Earl merging with a deep-layer low and turning
northward or northwestward toward Newfoundland as an extratropical
low.  For now, the updated NHC forecast shows Earl slowing down
considerably to the southeast of Newfoundland on days 4 and 5.

GFS- and ECMWF-based SHIPS guidance show the strong shear currently
affecting Earl decreasing to moderate levels in about 12 hours, and
even to low levels in about 36 hours.  Combined with very warm
waters and a possible positive trough interaction during the next
24 hours, Earl is forecast to strengthen and is likely to become a
major hurricane in the next 36 to 48 hours while passing to the
southeast of Bermuda.  Weakening is expected to begin after day 3
due to colder waters and another increase in shear, and Earl is
forecast to become extratropical by day 4 while it interacts with
the aforementioned deep-layer low to the southeast of Atlantic
Canada.


KEY MESSAGES:

1.  Although Earl's center is forecast to pass southeast of Bermuda,
the wind field is expected to grow, with tropical-storm-force winds
forecast to spread across the island beginning Thursday afternoon
and continuing through Friday morning.

2.  Swells generated by Earl are expected to reach Bermuda by
tonight.  These swells are likely to cause life-threatening surf and
rip current conditions through Friday.  Please consult products from
your local weather office.


FORECAST POSITIONS AND MAX WINDS

INIT  07/0900Z 25.3N  65.9W   70 KT  80 MPH
 12H  07/1800Z 26.4N  65.8W   75 KT  85 MPH
 24H  08/0600Z 27.9N  65.6W   85 KT 100 MPH
 36H  08/1800Z 29.7N  64.9W   95 KT 110 MPH
 48H  09/0600Z 31.8N  63.2W  105 KT 120 MPH
 60H  09/1800Z 34.5N  60.1W  110 KT 125 MPH
 72H  10/0600Z 37.9N  55.7W  110 KT 125 MPH
 96H  11/0600Z 43.6N  48.3W   75 KT  85 MPH...POST-TROP/EXTRATROP
120H  12/0600Z 45.3N  46.7W   50 KT  60 MPH...POST-TROP/EXTRATROP

$$
Forecaster Berg
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