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Tropical Storm Victor Forecast Discussion Number 3
2021-09-30 04:47:28| National Hurricane Center (Atlantic)
Issued at 200 AM CVT Thu Sep 30 2021 000 WTNT45 KNHC 300247 TCDAT5 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. FORECAST POSITIONS AND MAX WINDS 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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