[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 052056
TCDAT1

Tropical Storm Earl Discussion Number  12
NWS National Hurricane Center Miami FL       AL062022
500 PM AST Mon Sep 05 2022

Earl's structure continues to evolve this afternoon and looks a
little better organized on convectional satellite imagery. The
deepest convective activity now is located primarily north of the
low-level circulation center which still appears partially exposed,
but has become increasingly shrouded by the growing cirrus canopy.
GLM lightning data suggests that these cold convective tops are
continuing to rotate up-shear against the moderate westerly vertical
wind shear and may be helping to better align the low and mid-level
centers, though the lack of recent microwave data makes this
improved structure hard to confirm. However, data received by this
afternoon's Air Force Reserve Reconnaissance aircraft suggests the
pressure has not yet fallen much from this morning. Subjective
satellite intensity estimates have a wide range, with TAFB at
T4.0/65-kt while SAB is at T3.0/45-kt. The initial intensity this
advisory will remain 55 kt. Another NOAA-P3 reconnaissance mission
is en route to investigate Earl further this evening.

Earl appears to now be moving due north, with the latest motion
estimated at 360/5 kt. The short-term track forecast reasoning
remains unchanged, with only a general slow northward motion
anticipated for the next 24-36 hours as the storm moves into a
weakness created in the larger-scale ridging over Earl currently.
The biggest change beyond that time period is that the latest ECMWF
run has come in better agreement with the GFS showing a more
significant deep-layer trough digging northeast of Earl, resulting
in more acceleration to the northeast in the latter portion of the
forecast period. The overall track guidance this cycle is now much
faster in the day 3-5 time-frame, and the latest NHC track has also
been made faster to the northeast. However, this forecast is not yet
quite as fast as the consensus aids. Further adjustments may be
needed in subsequent forecasts if this more progressive trend
persists in the guidance. Regardless, along-track uncertainty for
Earl remains larger than normal during this time frame.

The current satellite structure suggests that Earl may be able to
hold its own or even intensify a bit more in the short term,
especially if the low and mid-level centers continue to become
better aligned. While vertical wind shear in the ECMWF- and
GFS-SHIPS is rather high the next 36 hours, between 25-30 kt, this
shear is more driven by the high westerly upper-level winds at 200
mb. The more shallow mid-level shear layer appears to be lower
magnitude over the next 36 hours, and some recent research suggests
that mid-level shear is more influential for tropical cyclone
intensity change. Regardless, even the deep-layer shear decreases to
under 10 kt after 60 hours, and Earl is still forecast to to peak in
intensity in about 4-5 days as a Category 3 hurricane. During the
forecast period, Earl is also expected to grow in size
significantly, with the 34-kt wind radii extending more than 250 n
mi by day 5. The latest intensity forecast has also moved the
intensification rate to earlier in the forecast period, in general
agreement with the latest HCCA and ICON consensus aids.

KEY MESSAGES:

1.  Ongoing Heavy rainfall from Earl's feeder bands still could lead
to limited flash, urban, and small stream flooding impacts over the
Leeward Islands, U.S. and British Virgin Islands, and Puerto Rico
this afternoon and evening. Rapid rises on rivers and mudslides in
areas of steep terrain are possible in Puerto Rico. Considerable
flood impacts cannot be ruled out in areas that receive heavier
rainfall totals.

2. Earl's center is expected to pass to the southeast of Bermuda in
around 3-4 days. However, the wind field of the tropical cyclone is
expected to increase significantly, and interests on the island
should continue to monitor the progress of the storm closely.


FORECAST POSITIONS AND MAX WINDS

INIT  05/2100Z 22.2N  65.2W   55 KT  65 MPH
 12H  06/0600Z 22.9N  65.3W   60 KT  70 MPH
 24H  06/1800Z 23.8N  65.5W   60 KT  70 MPH
 36H  07/0600Z 24.8N  65.5W   65 KT  75 MPH
 48H  07/1800Z 26.0N  65.4W   70 KT  80 MPH
 60H  08/0600Z 27.6N  65.2W   75 KT  85 MPH
 72H  08/1800Z 29.2N  64.4W   90 KT 105 MPH
 96H  09/1800Z 33.0N  60.5W  105 KT 120 MPH
120H  10/1800Z 37.0N  56.5W  100 KT 115 MPH

$$
Forecaster Papin
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