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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
 
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