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Tropical Storm Wanda Forecast Discussion


000
WTNT41 KNHC 021435
TCDAT1

Tropical Storm Wanda Discussion Number  11
NWS National Hurricane Center Miami FL       AL212021
300 PM GMT Tue Nov 02 2021

After the overnight burst of deep convection and associated improved 
organization, dry air has wrapped into the system from all quadrants 
and has temporarily eroded Wanda's inner-core convection. Despite 
the recent convective degradation, visible satellite imagery 
indicates that the cyclone's low-level circulation has improved, 
with well-defined, curved low-level cloud lines and shallow 
convection having become more evident. Based on improved low-level 
structure, the intensity estimate remains at 45 kt despite the 
overall loss of deep convection.

During the past 6 h, Wanda has made the expected sharp left-hand 
turn and is now moving northward, or 010/08 kt. There are no 
significant changes to the previous forecast track or reasoning. 
Over the next couple of days, the latest model guidance is in 
excellent agreement that Wanda should remain embedded within a 
deep-layer trough, and gradually turn toward the north-northeast 
later today, followed by a northeastward motion tonight and 
Wednesday as the cyclone moves through the trough-to-ridge flow 
pattern. By 48-60 hours, the cyclone is forecast to move toward the 
east and east-southeast as a ridge builds to the northwest and west 
of Wanda.  The new NHC official forecast track is very similar to 
the previous advisory track, and lies close to the middle of the 
simple- and corrected-consensus guidance envelope.

The aforementioned improved low-level structure should act to force 
new convection later today and especially tonight during the 
nocturnal convective maximum period. Thus, Wanda has another 24-36 h 
to strengthen while the system remains over marginally warm 
sea-surface temperatures (SST) near 23 deg C and within a 
relatively low vertical wind shear environment. Thereafter, slow but 
steady weakening is likely due to an increase in southwesterly wind 
shear, a decrease in mid-tropospheric moisture, and a decrease in 
SSTs. However, baroclinic effects associated with an approaching 
mid-tropospheric trough from the west could partially offset the 
weakening process. Wanda is expected become a post-tropical cyclone 
around 72 h, but this could be delayed if the baroclinic forcing on 
day 3 ends up stronger than currently expected.  The new official 
intensity forecast is essentially just an update of the previous 
intensity forecast, and is close to an average of the intensity 
consensus models IVCN, NOAA-HCCA, and FSSE.


FORECAST POSITIONS AND MAX WINDS

INIT  02/1500Z 35.6N  40.6W   45 KT  50 MPH
 12H  03/0000Z 37.0N  40.0W   45 KT  50 MPH
 24H  03/1200Z 38.8N  39.6W   50 KT  60 MPH
 36H  04/0000Z 40.7N  39.5W   45 KT  50 MPH
 48H  04/1200Z 42.1N  39.3W   45 KT  50 MPH
 60H  05/0000Z 42.7N  38.1W   45 KT  50 MPH
 72H  05/1200Z 42.5N  36.1W   45 KT  50 MPH...POST-TROPICAL
 96H  06/1200Z 41.0N  33.0W   45 KT  50 MPH...POST-TROPICAL
120H  07/1200Z 42.5N  29.5W   40 KT  45 MPH...POST-TROPICAL

$$
Forecaster Stewart



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