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| #1068166 (Received by flhurricane at: 10:57 PM 01.Nov.2021) TCDAT1 Tropical Storm Wanda Discussion Number 9 NWS National Hurricane Center Miami FL AL212021 300 AM GMT Tue Nov 02 2021 The satellite presentation of Wanda indicates the system is struggling with the effects of dry air and vertical wind shear tonight. The center of the cyclone is partially exposed, with dry mid-level air wrapping around the western and southern portions of its circulation. The moderate to deep convection associated with Wanda is displaced to the east and northeast of its center. A partial ASCAT-B pass shows tropical-storm-force winds are occurring in the southwestern quadrant of the storm. The latest objective and subjective satellite estimates range from 35-40 kt, and the initial intensity is held at 40 kt for this advisory. Wanda is moving east-northeastward, or 75/6 kt. The complex steering pattern over the northern Atlantic during the next several days makes for a challenging track forecast. In the near term, Wanda is expected to turn toward the northeast and north on Tuesday and Wednesday as the cyclone is steered by a mid- to upper-level trough over the north-central Atlantic. The track models are well clustered for the first couple days of the forecast period, but then significant differences emerge in the guidance at days 3-5. The new GFS deviates from its previous run and shows the cyclone accelerating eastward to northeastward as it eventually merges with an approaching baroclinic system late this week. Meanwhile, the ECMWF shows a narrow ridge building to the north and west of Wanda, which slows its forward motion and eventually turns the cyclone southward. The other global models generally lie somewhere in between the divergent GFS/ECMWF solutions. Given the above average uncertainty and lack of run-to-run model continuity, the NHC official track forecast remains near or between the HCCA and TVCA consensus aids. Overall, little change in strength is expected during the next several days. While the deep-layer shear is expected to diminish through midweek, Wanda is forecast to be moving over sub-20 deg C SSTs by Thursday. Thus, the cyclone only has a small window in which to sustain enough deep, organized convection to support much strengthening. Of course, if Wanda deviates from the official track and races deeper into the mid-latitudes as shown by the GFS, it would encounter even more hostile conditions and likely transition to a post-tropical cyclone sooner than forecast. The official NHC intensity forecast lies closest to the IVCN consensus aid, and allows for a bit of strengthening in the near term similar to the previous forecast. FORECAST POSITIONS AND MAX WINDS INIT 02/0300Z 34.5N 41.6W 40 KT 45 MPH 12H 02/1200Z 35.3N 40.9W 45 KT 50 MPH 24H 03/0000Z 36.9N 40.2W 45 KT 50 MPH 36H 03/1200Z 38.8N 39.9W 45 KT 50 MPH 48H 04/0000Z 40.9N 39.7W 45 KT 50 MPH 60H 04/1200Z 42.3N 39.2W 45 KT 50 MPH 72H 05/0000Z 42.9N 38.0W 45 KT 50 MPH 96H 06/0000Z 43.2N 33.4W 45 KT 50 MPH...POST-TROPICAL 120H 07/0000Z 43.0N 29.0W 40 KT 45 MPH...POST-TROPICAL $$ Forecaster Reinhart |
