Atlantic Basin Tropical Cyclones

Tropical Storm Wanda Forecast Discussion


000
WTNT41 KNHC 060845
TCDAT1

Tropical Storm Wanda Discussion Number  26
NWS National Hurricane Center Miami FL       AL212021
900 AM GMT Sat Nov 06 2021

Wanda's convective structure has continued to evolve this morning, 
with two earlier bands situated east and west of the well-defined 
center now having consolidated into a solid band of convection with 
cloud tops of -50C to -57C wrapping around the eastern semicircle. 
The initial intensity remains 45 kt for this advisory based on 
continuity with earlier 40-45 kt ASCAT data and the recently 
improved convective structure.

The initial motion estimate is southward or 180/04 kt. Wanda is 
expected to slow down further this morning and then turn sharply 
northeastward this afternoon as a narrow mid-/upper-level shortwave 
ridge passes to the north of the cyclone. A strong deep-layer trough 
and associated frontal system are then forecast to approach Wanda 
from the west by tonight, causing the cyclone to accelerate 
northeastward on Sunday and Monday. The front is forecast to catch 
up with Wanda in the 36-48-h period, resulting in extratropical 
transition before the system is absorbed by a large, deepening 
extratropical cyclone over the northern Atlantic early next week. 
The latest NHC model guidance is in excellent agreement on this 
developing forecast track scenario, and the official forecast track 
lies very near the the middle of the tightly packed simple- and 
corrected-consensus guidance envelope.

Wanda's is now over what will be the warmest water for the remainder 
of the cyclone's lifetime. The deep-layer shear is forecast to 
remain around 10-15 kt for the next 24 h or so, while colder 
aloft overspreads the cyclone, creating a little more instability. 
This combination of positive environmental factors should continue 
to produce deep convection near Wanda's center, possibly resulting 
in some slight strengthening before the system becomes an 
extratropical cyclone. The new NHC intensity forecast is basically 
identical to the previous advisory, and closely follows a blend of 
the various intensity consensus models.


FORECAST POSITIONS AND MAX WINDS

INIT  06/0900Z 37.4N  38.3W   45 KT  50 MPH
 12H  06/1800Z 37.5N  37.7W   45 KT  50 MPH
 24H  07/0600Z 39.4N  35.0W   45 KT  50 MPH
 36H  07/1800Z 43.6N  29.5W   50 KT  60 MPH
 48H  08/0600Z 48.7N  22.2W   50 KT  60 MPH...POST-TROP/EXTRATROP
 60H  08/1800Z 54.2N  12.8W   40 KT  45 MPH...POST-TROP/EXTRATROP
 72H  09/0600Z...DISSIPATED

$$
Forecaster Stewart



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