[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT41 KNHC 040835
TCDAT1

Tropical Storm Earl Discussion Number   6
NWS National Hurricane Center Miami FL       AL062022
500 AM AST Sun Sep 04 2022

Satellite imagery, surface observations, and WSR-88D radar data
from Puerto Rico indicate that Earl remains disorganized due to
ongoing southwesterly vertical wind shear, and that the center is
rather tricky to locate.  One vorticity center, associated with a
fresh convective burst, is located just north of the Virgin
Islands. However, TAFB and SAB fixed on another cloud area farther
north, while the radar data suggests another vorticity center in
the deep convection to the northeast of the Virgin Islands.  The
advisory position is a mean center between these features and is a
little north of the new burst.  The satellite intensity estimates
are unchanged from earlier, so the initial intensity remains 45 kt.

The storm has slowed its forward motion, which is now 285/7 kt.
The track guidance is in good agreement that a break will form in
the subtropical ridge as a mid- to upper-level trough develops to
the northwest of Earl beginning later today.  This should cause the
cyclone to turn northwestward during the next 12-24 h, with a
northward motion likely from 24-72 h and a north-northeastward
motion from 72-120 h.  The track models are in good agreement on
the general direction of motion.  However, while the GFS is slower
than its previous forecast it is still faster than the rest of the
guidance.  The new forecast track is nudged to the right of the
previous forecast based on the overall shift of the guidance
envelope.  During the first 72 h, it is in best agreement with the
GFS and UKMET ensemble means, and after that time it lies close to
the various consensus models.

The ongoing shear is expected to continue through at least the next
72 h, and thus only gradual strengthening is likely during this
time as Earl moves over warm sea surface temperatures in a moist
environment.  After that time, the cyclone could interact with the
aforementioned trough in such a way to leave Earl in a more
favorable environment for intensification, and the dynamical
models forecast significant strengthening toward the end of the
forecast period.  The new intensity forecast has only minor
adjustments from the previous forecast, and for the first 72 h it is
close to the bulk of the intensity guidance.  After it time, the
forecast is below that of most of the guidance due to the
uncertainty of how favorable the environment will be.

Tropical-storm-force winds are still forecast to remain on the
northern and eastern side of the circulation, and 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 through tonight.


KEY MESSAGES:

1.  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 today.  Rapid
rises on rivers and mudslides in areas of steep terrain are possible
in Puerto Rico.

2.  Earl is forecast to pass to the north of the the Virgin Islands
and Puerto Rico today, and gusty winds, especially in squalls,
area possible on those islands.


FORECAST POSITIONS AND MAX WINDS

INIT  04/0900Z 19.5N  64.9W   45 KT  50 MPH
 12H  04/1800Z 20.1N  65.6W   45 KT  50 MPH
 24H  05/0600Z 21.1N  66.2W   50 KT  60 MPH
 36H  05/1800Z 22.0N  66.5W   50 KT  60 MPH
 48H  06/0600Z 23.0N  66.6W   55 KT  65 MPH
 60H  06/1800Z 24.0N  66.7W   60 KT  70 MPH
 72H  07/0600Z 25.0N  66.5W   60 KT  70 MPH
 96H  08/0600Z 26.5N  65.5W   70 KT  80 MPH
120H  09/0600Z 28.5N  63.5W   85 KT 100 MPH

$$
Forecaster Beven
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