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Tropical Storm Victor Forecast Discussion Number 11
2021-10-02 04:46:02| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Fri Oct 01 2021 000 WTNT45 KNHC 020245 TCDAT5 Tropical Storm Victor Discussion Number 11 NWS National Hurricane Center Miami FL AL202021 1100 PM AST Fri Oct 01 2021 The structure of Victor this evening continues to degrade with the low-level center becoming decoupled from the mid- to upper-level circulation associated with the deeper convection. While the tropical storm does continue to produce a region of deep convection with cloud tops colder than -70 C, this activity is organized in a linear band that is now more than 150 n mi northeast of the exposed low-level center as seen on Proxy-Vis satellite imagery. Both ASCAT-B/C clipped the western half of Victor's circulation, showing peak winds of 40 kt on the far edge of the pass. In addition, the latest subjective and objective satellite intensity estimates have been falling this evening. The latest intensity for this advisory has been lowered to 50 kt this advisory, assuming the scatterometer data missed higher wind values to the northeast of Victor closer to the convection. However, given Victor's current structure, this estimate may still be generous. Now that the low-level cloud swirl is readily apparent on satellite imagery, it is somewhat easier to track Victor this evening, with the estimated motion still west-northwest at 290/11 kt. Because the cyclone is also becoming more vertically shallow, the primarily steering feature will be a large low-level subtropical ridge centered to the north, which should guide Victor on a general west-northwestward to northwestward heading for the next 2-3 days at a similar forward motion. The latest track guidance has shifted westward this cycle, likely in response to Victor being a weaker cyclone less coupled to the deep convection. The latest NHC track forecast was also shifted a bit west over the forecast period, staying closer to the consensus aids HCCA and TVCA, though it is worth nothing this is still not as far west as the latest GFS or ECMWF runs. While the deep-layer 200-850 hPa vertical wind shear has not been prohibitively strong today (15-20 kt), more substantial mid-level shear underneath the outflow layer (25-30 kt) appears to be responsible for the current disheveled appearance of Victor. This shear is related to a large upper-level cutoff low upstream of the tropical storm. Even though the current shear is not expected to increase much more in the short-term, the mid-level environment over Victor is expected to continue drying as the existing shear will import very dry air upstream into the core of the cyclone. All of the guidance responds to these unfavorable conditions by gradually weakening Victor over the next few days, and the latest NHC intensity forecast has been lowered a bit more compared to the previous advisory. While pulses of deep convection are likely to continue north of Victor over the next several days, the circulation is expected to gradually lose definition, and the global and high-res regional hurricane models now open up the system into a trough between 72-96 hours. The latest NHC intensity forecast now follows suit, showing dissipation by 96 hours. FORECAST POSITIONS AND MAX WINDS INIT 02/0300Z 12.3N 35.3W 50 KT 60 MPH 12H 02/1200Z 13.2N 36.9W 45 KT 50 MPH 24H 03/0000Z 14.6N 38.7W 40 KT 45 MPH 36H 03/1200Z 16.5N 40.6W 40 KT 45 MPH 48H 04/0000Z 18.5N 42.6W 35 KT 40 MPH 60H 04/1200Z 20.6N 44.7W 35 KT 40 MPH 72H 05/0000Z 22.2N 46.5W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 06/0000Z...DISSIPATED $$ Forecaster Papin
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