Atlantic Basin Tropical Cyclones

Subtropical Storm Wanda Forecast Discussion


000
WTNT41 KNHC 010846
TCDAT1

Subtropical Storm Wanda Discussion Number   6
NWS National Hurricane Center Miami FL       AL212021
900 AM GMT Mon Nov 01 2021

Wanda is now located to the west of the axis of the upper-level 
trough that it is embedded in.  As a result, significant northerly 
vertical wind shear has developed over the storm, and between this 
and continuing dry air entrainment the associated convection is 
less organized than 24 h ago.  Various subjective and objective 
satellite intensity estimates are in the 40-50 kt range, and based 
on continuity from earlier ASCAT data the initial intensity is held 
at 45 kt.

After the earlier southwestward motion, Wanda is now turning 
southeastward with the initial motion of 125/6.  The storm and the 
upper-level trough should move northeastward later today and then 
northward by 36-48 h as southerly flow between a large 
mid-latitude trough over the northwestern Atlantic and a 
ridge east of Wanda becomes the dominant steering mechanism. After 
72 h, another mid-latitude ridge is expected to build between Wanda 
and the western Atlantic trough, and as a result the cyclone is 
expected to turn eastward and then southward.  The latest track 
guidance shows a more northward motion than the previous guidance 
between 36-60 h, and a more southward motion after 96 h.  The new 
forecast track has been nudged in those directions. 

The intensity guidance suggests little change in strength during 
the next several days as dry air and relatively cool SSTs continue 
to affect the system.  However, the current shear is expected to 
decrease during the next 24-36 h, and this should help the system 
to transition to a tropical cyclone.  By 120 h, Wanda is expected 
to become a post-tropical low as cooler sea surface temperatures 
and an even dryer air mass cause the convection to dissipate.  The 
new intensity forecast is unchanged from the previous forecast.


FORECAST POSITIONS AND MAX WINDS

INIT  01/0900Z 34.5N  39.9W   45 KT  50 MPH
 12H  01/1800Z 34.3N  43.3W   45 KT  50 MPH
 24H  02/0600Z 34.9N  42.1W   45 KT  50 MPH...TROPICAL CYCLONE
 36H  02/1800Z 36.2N  41.3W   45 KT  50 MPH
 48H  03/0600Z 38.2N  40.9W   45 KT  50 MPH
 60H  03/1800Z 40.1N  40.7W   45 KT  50 MPH
 72H  04/0600Z 41.5N  40.0W   45 KT  50 MPH
 96H  05/0600Z 43.0N  36.5W   45 KT  50 MPH
120H  06/0600Z 41.0N  33.5W   40 KT  45 MPH...POST-TROPICAL

$$
Forecaster Beven



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