[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT42 KNHC 200859
TCDAT2

Tropical Storm Rose Discussion Number   5
NWS National Hurricane Center Miami FL       AL172021
500 AM AST Mon Sep 20 2021

Rose remains a sheared tropical storm with the low-level center
located near the eastern edge of the convective cloud mass based on
an earlier 0359Z AMSR2 microwave overpass. These same data also
revealed that a well-defined mid-level circulation center was
located about 80-90 nmi west of the low-level center, an indication
of the magnitude and effect of the mid-level shear impinging on the
cyclone. The intensity of 35 kt is being maintained for this
advisory based on subjective Dvorak satellite intensity estimates of
35 from both TAFB and SAB. Objective estimates from UW-CIMSS are
higher at 45-55 kt, which are considered to be unrepresentative due
to the severe westward tilt of Rose's vortex column.

The initial motion estimate is northwestward or 315/13 kt.  Rose is
expected to move generally northwestward around the southwestern and
western periphery of a strong subtropical ridge during the next few
days.  By day 4 and beyond, a mid- to upper-level trough over the
north-central Atlantic is forecast to dig southeastward, causing the
cyclone to turn northward.  The latest NHC model guidance remains in
excellent agreement on this track scenario through 72 hours, but
then diverge significantly thereafter owing to whether Rose weakens
to shallow system or remains a little stringer and deeper. The
weaker solutions go more toward the northwest and the stronger
solutions take Rose northeastward. The NHC forecast track on days 4
and 5 is a blend of these two extremes.

Rose only has about 24 hours over warm waters and in a weak vertical
wind shear regime that will allow for some addition strengthening to
occur. On days 2-5, however, increasing westerly shear is expected
to induce some gradual weakening.  Rose is forecast to weaken to a
tropical depression by 96 hours, although some of the models suggest
that weakening could occur faster than indicated below, and that
Rose could degenerate into a remnant low by the end of the forecast
period.


FORECAST POSITIONS AND MAX WINDS

INIT  20/0900Z 15.9N  32.6W   35 KT  40 MPH
 12H  20/1800Z 17.5N  33.8W   40 KT  45 MPH
 24H  21/0600Z 19.8N  35.5W   40 KT  45 MPH
 36H  21/1800Z 21.7N  36.7W   35 KT  40 MPH
 48H  22/0600Z 23.0N  37.7W   35 KT  40 MPH
 60H  22/1800Z 24.2N  38.7W   35 KT  40 MPH
 72H  23/0600Z 25.2N  39.8W   30 KT  35 MPH
 96H  24/0600Z 27.3N  41.3W   25 KT  30 MPH
120H  25/0600Z 29.2N  40.6W   25 KT  30 MPH

$$
Forecaster Stewart
This weather bulletin was brought to you by:
www.nashvilleweather.net