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Tropical Storm Victor Forecast Discussion

WTNT45 KNHC 010842

Tropical Storm Victor Discussion Number   8
NWS National Hurricane Center Miami FL       AL202021
500 AM AST Fri Oct 01 2021

Infrared and microwave satellite imagery indicate that Victor has 
continued to become a little better organized, with a 0342Z AMSR2 
overpass showing that a 75-percent-closed mid-level eye feature had 
formed. However, both data sources also revealed that a pronounced 
dry slot has formed in the southeastern quadrant. Upper-level 
outflow remains well established in all quadrants except to the 
south where it is somewhat restricted. Despite the slightly improved 
satellite signatures, subjective and objective intensity 
classifications have not changed since the previous advisory, so the 
intensity remains at 50 kt for this advisory.

The initial motion estimate is 305/13 kt. Victor has made a slight 
jog toward the northwest, but this is likely a temporary motion due 
to redevelopment of the center farther into the convective cloud 
shield. The cyclone should resume a west-northwestward motion later 
today and maintain that motion for another day or so as Victor moves 
along the southwestern periphery of a strong subtropical ridge 
situated over the east-central Atlantic. The latest model runs 
continue to show a broad mid- to upper-level low developing over the 
central Atlantic to the west of Victor in the 24-72-h forecast 
period, which will act to erode the western portion of the ridge and 
create a deep-layer southerly flow pattern across the cyclone.  As a 
result, Victor is forecast to turn northwestward by the weekend and 
then move northward by early next week. Owing to a more robust 
mid-/upper-level low forecast to develop than previously expected, 
the latest NHC track guidance has made a significant westward shift 
by at least 100 nmi at 72 h and nearly 200 nmi on days 4 and 5. This 
westward shift is due to Victor now forecast to weaken faster and 
become more vertically shallow, with the dominant steering flow 
shifting to low-level easterlies. The new NHC track forecast has 
also been shifted westward, but not as far west as the tightly 
packed consensus models, all of which lie well to the east of the 
westernmost GFS solution.

Victor is expected to remain in a somewhat favorable environment for 
the next 18 h or so, which should allow for at least some slight 
strengthening to occur.  Thereafter, however, southwesterly 
deep-layer vertical wind shear is forecast by the GFS and ECMWF 
models to increase to 20-25 kt in 24 hours and 30-35 kt by 72 h. 
These hostile shear conditions, in conjunction with a drier air 
mass, should result in gradual weakening during the 24-120-h period, 
with Victor becoming a remnant low on day 5. The new official 
intensity forecast is a little below the previous advisory, but it 
is above the consensus intensity models ICON, HCCA, and FSSE, due to 
the recent development of the aforementioned primitive eye feature.


INIT  01/0900Z 11.7N  32.3W   50 KT  60 MPH
 12H  01/1800Z 12.4N  33.6W   55 KT  65 MPH
 24H  02/0600Z 13.4N  35.3W   55 KT  65 MPH
 36H  02/1800Z 14.9N  36.8W   50 KT  60 MPH
 48H  03/0600Z 16.7N  38.6W   45 KT  50 MPH
 60H  03/1800Z 19.0N  40.5W   40 KT  45 MPH
 72H  04/0600Z 21.0N  42.0W   35 KT  40 MPH
 96H  05/0600Z 24.0N  44.0W   30 KT  35 MPH
120H  06/0600Z 28.0N  45.0W   25 KT  30 MPH...POST-TROP/REMNT LOW

Forecaster Stewart

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