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Tropical Storm Victor Forecast Discussion Number 8
2021-10-01 10:42:18| National Hurricane Center (Atlantic)
Issued at 500 AM AST Fri Oct 01 2021 000 WTNT45 KNHC 010842 TCDAT5 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. FORECAST POSITIONS AND MAX WINDS 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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