Atlantic Basin Tropical Cyclones

Tropical Storm Wanda Forecast Discussion


000
WTNT41 KNHC 020239
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



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