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Tropical Storm Victor Forecast Discussion

WTNT45 KNHC 300247

Tropical Storm Victor Discussion Number   3
NWS National Hurricane Center Miami FL       AL202021
200 AM CVT Thu Sep 30 2021

Victor has changed little in organization since the last advisory, 
with a large circulation and a complex of convective bands mainly in 
the northern semicircle.  Satellite intensity estimates from TAFB 
and SAB remain at or near 35 kt, as do other objective intensity 
estimates.  Thus, the initial intensity is still 35 kt, although the 
most recent ASCAT-A data suggests the possibility that this is a 
little generous.

The center has moved or re-formed a bit to the west during the past 
several hours, although the longer-term motion still seems to be to 
the west-northwest at 290/11 kt.  Other than the more westerly 
initial position, there is little change to the forecast philosophy 
or the forecast track since the last advisory.  Victor is forecast 
to move west-northwestward for the next 36 h or so as it is steered 
by the flow on the south side of a deep-layer ridge.  By 48 h, the 
global models forecast the western periphery of the ridge to get 
eroded by to a mid- to upper-level low over the subtropical central 
Atlantic. This evolution should cause the cyclone to turn 
northwestward at that time, followed by a northward turn by the end 
of the forecast period.  There remains a fair amount of spread in 
the timing and location of the northward turn with the GFS and HWRF 
still on the right side of the guidance envelope and the ECMWF 
showing the slowest and westernmost solution. The new forecast track 
is in the center of the guidance envelope and lies very close to the 
various consensus models.

For the next 36-48 h, Victor is expected to remain in an environment 
of warm sea surface temperatures and light vertical wind shear.  
This should allow steady strengthening, and rapid strengthening 
cannot be ruled out if the storm develops a better defined inner 
core.  Based on a steady strengthening scenario, the new intensity 
forecast is identical to the previous one, taking Victor to 
hurricane intensity in 36 h with a peak intensity of 70 kt in 48 h.  
After that time, the aforementioned upper-level low is expected to 
cause significant shear over Victor while the cyclone moves into a 
drier air mass.  This combination should cause the cyclone to 
weaken, and it is possible Victor could weaken faster than currently 
forecast after 60 hours.  The new official intensity forecast lies 
near the upper edge of the intensity guidance.


INIT  30/0300Z  8.4N  26.7W   35 KT  40 MPH
 12H  30/1200Z  8.9N  28.3W   45 KT  50 MPH
 24H  01/0000Z  9.7N  30.2W   55 KT  65 MPH
 36H  01/1200Z 10.6N  32.0W   65 KT  75 MPH
 48H  02/0000Z 11.8N  33.5W   70 KT  80 MPH
 60H  02/1200Z 13.4N  35.1W   70 KT  80 MPH
 72H  03/0000Z 15.5N  36.7W   60 KT  70 MPH
 96H  04/0000Z 20.5N  39.5W   45 KT  50 MPH
120H  05/0000Z 26.0N  41.0W   40 KT  45 MPH

Forecaster Beven

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