Atlantic Hurricane Feed

Subtropical Storm Wanda Forecast Discussion

WTNT41 KNHC 311453

Subtropical Storm Wanda Discussion Number   3
NWS National Hurricane Center Miami FL       AL212021
300 PM GMT Sun Oct 31 2021

Wanda is gradually taking on characteristics of a symmetric 
warm-core cyclone, with bands of organized convection now located 
across both the northern and southeastern portions of the 
circulation. The 500-mb heights are slowing rising, while some 
cirrus outflow is becoming evident to the north of the cyclone. 
Although Wanda is still considered a subtropical storm due to the 
presence of the surrounding baroclinic circulation and 
upper-trough, the baroclinic circulation has been getting more 
detached from the storm over time.  Even though the convective 
structure continues to evolve, this convection has not been able to 
become more concentrated near the system's core since last night. 
Therefore, the initial advisory intensity remains 45 kt, which is 
consistent with the latest average of the satellite intensity 
estimates from TAFB, and UW-CIMSS ADT and SATCON.

The storm has slowed its forward motion and is now moving at 100/07 
kt.  A turn to the southeast is expected today as Wanda wobbles 
within the upper-level tropospheric trough that it is embedded 
within.  The upper-trough is forecast to lift out on Monday, 
leaving Wanda within the weak steering flow near a cutoff mid-level 
trough.  By Tuesday, a ridge is forecast to build to the east of 
the cyclone, resulting in a turn to the northeast or north, along 
with an increase in forward speed.  By late this week, Wanda should 
accelerate northeastward within the southwesterly mid-latitude flow. 
The model guidance is in good agreement on this track scenario, and 
the latest NHC track forecast is very similar to the previous one.

Despite being over sea surface temperatures below the ideal warmth 
to support a classic tropical cyclone, the colder-than-typical upper 
tropospheric temperatures over Wanda should continue to help support 
deep convection for the next few days.  Therefore, some slight 
strengthening is possible during that time. As mentioned above, the 
upper-trough is expected to leave Wanda behind by Monday, which 
should allow the cyclone to complete a tropical transition by that 
time.  Various global model solutions within the Florida State 
University cyclone phase evolution forecasts agree with this 
scenario taking place over the next 24 h.  After 72 h, decreasing 
water temperatures in the path of Wanda should cause the cyclone to 
weaken and become post-tropical by the end of the 5-day forecast 
period.  The latest NHC intensity forecast is unchanged from the 
previous one, with the only change being the tropical phase of 
Wanda beginning Monday. 


INIT  31/1500Z 36.4N  43.2W   45 KT  50 MPH
 12H  01/0000Z 35.9N  42.8W   50 KT  60 MPH
 24H  01/1200Z 34.9N  42.4W   50 KT  60 MPH...TROPICAL CYCLONE
 36H  02/0000Z 34.8N  41.2W   50 KT  60 MPH
 48H  02/1200Z 35.6N  40.0W   50 KT  60 MPH
 60H  03/0000Z 37.4N  39.1W   50 KT  60 MPH
 72H  03/1200Z 39.4N  38.7W   45 KT  50 MPH
 96H  04/1200Z 43.4N  37.3W   45 KT  50 MPH
120H  05/1200Z 47.2N  30.0W   40 KT  45 MPH...POST-TROPICAL

Forecaster Latto

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