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| #1068397 (Received by flhurricane at: 5:03 PM 03.Nov.2021) TCDAT1 Tropical Storm Wanda Discussion Number 16 NWS National Hurricane Center Miami FL AL212021 900 PM GMT Wed Nov 03 2021 Wanda`s overall convective pattern has continued to improve since the previous advisory with a curved convective band now wrapping almost completely around the center, resulting in a 50-60-nmi wide banded eye feature. However, the horizontal thickness of the convective band has been waxing and waning, and cloud tops are only around -50C to -55C. Satellite intensity estimates from TAFB and SAB are a consensus T3.0/45 kt, while UW-CIMSS SATCON intensity estimates range from 34 kt to 44 kt, respectively. Based on these data, Wanda`s intensity is being maintained at 45 kt. Although a distinct eye feature is now evident, which would suggest a stronger storm, a lower intensity is warranted since the cooler water beneath the cyclone is likely creating a more stable boundary layer, which is likely inhibiting the normal downward mixing of higher winds aloft. This physical assumption is supported by weaker wind speeds noted in earlier scatterometer surface wind data. The initial motion estimate is a little east of due north, or 010/09 kt. There is no significant change to the previous forecast track and rationale. An approaching mid-/upper-level trough from the west should continue to lift Wanda northward for the next day or so, followed by slowing and a sharp turn to the east by Thursday night as the aforementioned trough weakens and lifts out to the north of the cyclone. Subsequent ridging behind the trough will then force Wanda southeastward to southward on Friday, followed by another abrupt turn and acceleration to the northeast on Saturday as a second and stronger deep-layer trough captures the cyclone. Despite this complexity in the evolving steering pattern, the latest NHC model guidance is in very agreement throughout the 120-h forecast period on this track scenario. The new NHC forecast track is very similar to the previous advisory track, and lies near or slightly to the right of the tightly packed simple- and corrected-consensus track models. The improved inner-core convective structure argues for at least some slight strengthening during the next couple of days despite the expected 20-21-deg-C sea-surface temperatures (SST) beneath the cyclone. Some cooling aloft associated with the aforementioned second upper-level trough may help to offset the negative effects of the relatively cool SSTs on day 3. In the 96-120-h period, Wanda is expected to interact, and eventually merge, with a cold front and become an extratropical low pressure system with gale-force winds. The new official intensity forecast is very similar to the previous advisory, and closely follows a blend of the intensity consensus models IVCN, NOAA-HCCA, and Florida State FSSE. FORECAST POSITIONS AND MAX WINDS INIT 03/2100Z 39.8N 39.5W 45 KT 50 MPH 12H 04/0600Z 41.0N 39.4W 50 KT 60 MPH 24H 04/1800Z 41.9N 39.1W 50 KT 60 MPH 36H 05/0600Z 41.8N 38.0W 50 KT 60 MPH 48H 05/1800Z 40.3N 37.0W 50 KT 60 MPH 60H 06/0600Z 38.8N 36.9W 45 KT 50 MPH 72H 06/1800Z 38.1N 36.6W 45 KT 50 MPH 96H 07/1800Z 42.4N 31.5W 45 KT 50 MPH...POST-TROP/EXTRATROP 120H 08/1800Z 51.5N 19.2W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Stewart |
