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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
 
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