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Subtropical Storm Teresa Forecast Discussion


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000
WTNT44 KNHC 242056
TCDAT4

Subtropical Storm Teresa Discussion Number   1
NWS National Hurricane Center Miami FL       AL192021
500 PM AST Fri Sep 24 2021

The disturbance just north of Bermuda interacting with a mid- to 
upper-level low has developed a prominent band of deep convection
within its eastern semicircle as well as a well-defined surface 
center. Additionally, the system is not displaying any significant 
baroclinicity (i.e., frontal boundaries), so it is not an 
extratropical cyclone.  All of which indicates that the system has 
evolved into a subtropical cyclone. ASCAT-C scatterometer data from 
1440Z suggested peak winds were around 40 kt, which is the basis 
for calling the system Subtropical Storm Teresa.

The system is moving toward the northwest at 12 kt is it rounds the 
northern part of the mid- to upper-level low.  By Saturday, Teresa 
should turn northward and then northeastward, as it begins to be 
caught up in the mid-latitude westerlies. The forecast is based upon 
the TVCN track consensus technique.

Teresa will not be long-lived.  A  developing extratropical system 
forming off of New England should absorb Teresa between 36 and 48 
hours.  Until then, the subtropical storm has a small window to 
intensify slightly while traversing lukewarm water and 
encountering moderate vertical shear.  If deep convection develops 
near the system's center, then Teresa could evolve into a tropical 
storm.  However, it is more likely that Teresa will remain a 
subtropical storm until dissipation in around two days.

It is worth noting that Teresa will likely be the 9th so-called 
"shortie" of the 2021 hurricane season -- systems that are short- 
lived and relatively weak.

FORECAST POSITIONS AND MAX WINDS

INIT  24/2100Z 34.5N  64.5W   40 KT  45 MPH
 12H  25/0600Z 35.4N  65.5W   45 KT  50 MPH
 24H  25/1800Z 36.3N  65.5W   45 KT  50 MPH
 36H  26/0600Z 37.2N  64.4W   40 KT  45 MPH
 48H  26/1800Z...DISSIPATED

$$
Forecaster Landsea