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| #1068696 (Received by flhurricane at: 10:54 PM 05.Nov.2021) TCDAT1 Tropical Storm Wanda Discussion Number 25 NWS National Hurricane Center Miami FL AL212021 300 AM GMT Sat Nov 06 2021 A dry mid-level environment appears to be hindering Wanda`s convective organization tonight. While infrared cloud top temperatures have warmed within the eastern semicircle, a more recent burst of moderately deep convection has been noted in the northwestern quadrant of Wanda. A timely ASCAT-B pass just before 0000 UTC revealed a broad swath of 40- to 45-kt winds within Wanda`s western semicircle. Based on these data, the initial intensity is held at 45 kt for this advisory. A narrow mid-level ridge to the north and west of Wanda is steering the cyclone southward. Its estimated motion is 185/8 kt, although Wanda has been moving more south-southwestward over the past several hours. The storm is expected to briefly slow down and meander over the central Atlantic this morning as the steering flow collapses. Then, increasing deep-layer southwesterly flow ahead of an approaching mid- to upper-level trough located near Atlantic Canada is forecast to cause Wanda to accelerate northeastward through early next week. The global models indicate that Wanda is likely to merge with a baroclinic zone by Sunday night, then become absorbed by a deepening extratropical cyclone over the northern Atlantic early next week. The latest track guidance is in good agreement, but it has trended faster with Wanda`s forward motion ahead of the trough, which will likely expedite its extratropical transition. Some along-track adjustments were made to the official NHC forecast, which now shows Wanda becoming extratropical in 48 h and becoming absorbed at 72 h. Wanda`s southward motion will bring the cyclone over slightly warmer (22 deg C) SSTs today, and cold air aloft could result in enough stability for Wanda to generate some more convection while the deep-layer shear diminishes to less than 10 kt. But the dry environment in which Wanda is embedded will continue to make it difficult for the storm`s organization to improve very much, as suggested by the latest GFS and ECMWF-model simulated satellite imagery. The latest NHC intensity forecast allows for just a bit of strengthening this weekend, in good agreement with the IVCN/HCCA consensus aids. By late Sunday and Monday, the aforementioned upper-level trough will bring strong south-southwesterly shear over Wanda while the cyclone moves over plummeting SSTs in the North Atlantic. Baroclinic processes and a fast forward motion could allow Wanda to briefly maintain its intensity, but a weakening trend should commence on Monday before the cyclone is absorbed. FORECAST POSITIONS AND MAX WINDS INIT 06/0300Z 38.0N 38.1W 45 KT 50 MPH 12H 06/1200Z 37.6N 38.0W 45 KT 50 MPH 24H 07/0000Z 38.4N 36.5W 45 KT 50 MPH 36H 07/1200Z 41.9N 32.4W 50 KT 60 MPH 48H 08/0000Z 47.4N 25.6W 50 KT 60 MPH...POST-TROP/EXTRATROP 60H 08/1200Z 54.0N 17.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 72H 09/0000Z...ABSORBED $$ Forecaster Reinhart |
