[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 031457
TCDAT1

Tropical Storm Earl Discussion Number   3
NWS National Hurricane Center Miami FL       AL062022
1100 AM AST Sat Sep 03 2022

Earl is a sheared tropical cyclone this morning, as the low-level
center is fully exposed to the west of the convective mass. NOAA
Hurricane Hunter aircraft data indicate the vortex remains tilted
due to about 15 kt of deep-layer southwesterly shear over the
cyclone. Recently, a more vigorous burst of convection has developed
closer to the center. The initial intensity is held at 35 kt based
on a blend of flight-level, SFMR, and dropsonde data from the
aircraft. It is noted that the surface pressure near the center has
fallen a couple of millibars since the previous advisory.

The cyclone remains on a west-northwestward heading as it is being
steered by the subtropical ridge. The guidance remains in very good
agreement that Earl will maintain a west-northwestward to
northwestward motion with a decrease in forward speed over the next
couple of days. As a weakness develops in the subtropical ridge
early next week, Earl is forecast to turn slowly northward and then
northeastward by days 3-5 as a mid- to upper-level trough develops
over the western Atlantic. Although there is increasing spread in
the track guidance during this period as to how quickly Earl
recurves, there is good overall agreement that the cyclone track
will remain over the open Atlantic waters. The official NHC forecast
has been adjusted slightly to the right of the previous one during
the 36-72 h window, based on similar trends noted in the guidance
consensus aids.

It appears that moderate deep-layer shear will continue to impact
Earl during the next couple of days. Therefore, only modest
strengthening is forecast during this time as the cyclone could
struggle to become vertically aligned and sustain convection near
its center. The intensity forecast is of lower confidence later in
the period once Earl begins turning northward. Although the vertical
shear is expected to persist or even strengthen, the potential for
favorable interaction with the upper trough should allow for
additional strengthening during this period, while the wind field of
the cyclone broadens. Most of the dynamical models support this
strengthening trend, and the latest NHC intensity forecast has been
adjusted upward some during this period. However, there remains
large spread in the intensity guidance at days 3-5, and the NHC
forecast remains on the lower end of the models.

Tropical-storm-force winds are forecast to remain on the northern
and eastern side of the circulation, and as a result, are not
expected to move across the northern Leeward Islands, the Virgin
Islands, or Puerto Rico.  However, gusty winds in squalls are
possible at these locations over the weekend.


KEY MESSAGES:

1.  Tropical Storm Earl is forecast to pass near or just to the
north of the northern Leeward Islands, the Virgin Islands, and
Puerto Rico over the weekend.  Gusty winds, especially in squalls,
area possible on those islands over the next day or two.

2.  Heavy rainfall from Earl is expected to lead to limited flash,
urban, and small stream flooding impacts over the Leeward Islands,
U.S. and British Virgin Islands, and Puerto Rico this weekend.
Rapid rises on rivers and mudslides in areas of steep terrain are
possible in Puerto Rico.


FORECAST POSITIONS AND MAX WINDS

INIT  03/1500Z 19.0N  62.4W   35 KT  40 MPH
 12H  04/0000Z 19.5N  63.6W   40 KT  45 MPH
 24H  04/1200Z 20.3N  65.0W   40 KT  45 MPH
 36H  05/0000Z 21.0N  65.7W   40 KT  45 MPH
 48H  05/1200Z 21.8N  66.3W   45 KT  50 MPH
 60H  06/0000Z 22.7N  66.6W   45 KT  50 MPH
 72H  06/1200Z 24.0N  66.6W   50 KT  60 MPH
 96H  07/1200Z 25.3N  65.9W   55 KT  65 MPH
120H  08/1200Z 27.0N  64.5W   60 KT  70 MPH

$$
Forecaster Reinhart
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