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Subtropical Storm Wanda Forecast Discussion


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WTNT41 KNHC 310233
TCDAT1

Subtropical Storm Wanda Discussion Number   1
NWS National Hurricane Center Miami FL       AL212021
1100 PM AST Sat Oct 30 2021

The non-tropical low that NHC has been monitoring for subtropical
transition over the central Atlantic appears to have completed the
process this evening.  Satellite images indicate that there are no
longer fronts attached to the low, and showers and thunderstorms
have become concentrated near the center.  The low has some tropical
characteristics (small radius of maximum wind and concentrated
convection) and some subtropical characteristics (co-located with an
upper-level trough and nearby fronts).  The system is designated as
a subtropical storm for now since there appears to be more support
for that status.  The initial intensity is estimated to be 45 kt
based on recent ASCAT data, which makes the cyclone Subtropical
Storm Wanda.

The storm has been moving east-southeastward at 18 kt.  A slower 
east-southeast to southeast motion is expected during the next day 
or so as Wanda moves with the deep-layer trough that it is embedded 
within.  After that time, the trough is expected to cut off, and 
Wanda will likely meander on Monday before turning sharply northward 
or northeastward by the middle of next week when the system moves 
in the flow between the low and a building ridge.  Most of the 
models agree on the general evolution, but there are notable speed 
differences.  The NHC track forecast lies near the various consensus 
aids.

Wanda will likely maintain its strength during the next several 
days.  Although the system will remain over relatively cool waters 
of about 23-24 C during the next couple of days, cold air aloft 
should aid in the continued development of deep convection and could 
allow the system to strengthen slightly during that time period.  
Beyond that time, Wanda should begin to move over cooler waters and 
that will likely end its opportunity to gain strength and lead to 
post-tropical transition by the end of the forecast period.  The 
models are in good agreement on keeping Wanda steady state, and the 
NHC intensity forecast lies near the middle of the guidance 
envelope.


FORECAST POSITIONS AND MAX WINDS

INIT  31/0300Z 36.2N  45.4W   45 KT  50 MPH
 12H  31/1200Z 35.8N  43.9W   45 KT  50 MPH
 24H  01/0000Z 35.3N  43.6W   50 KT  60 MPH
 36H  01/1200Z 34.3N  43.2W   50 KT  60 MPH
 48H  02/0000Z 33.8N  42.1W   45 KT  50 MPH
 60H  02/1200Z 34.5N  40.9W   45 KT  50 MPH
 72H  03/0000Z 36.4N  39.9W   45 KT  50 MPH
 96H  04/0000Z 41.4N  39.6W   45 KT  50 MPH
120H  05/0000Z 46.2N  35.4W   45 KT  50 MPH...POST-TROPICAL

$$
Forecaster Cangialosi



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