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Tropical Storm Theta Discussion Number  13
NWS National Hurricane Center Miami FL       AL302020
300 AM GMT Fri Nov 13 2020

The structure of Theta has been waxing and waning today with 
moderate convection attempting to wrap around the center, though the 
coldest cloud tops have been decaying before wrapping fully around. 
Earlier, there was a 2222 UTC partial ASCAT-B pass that showed peak 
winds of 40-45 kt on the south side of Theta. However the highest 
winds from this instrument the previous two nights were in the 
southwest quadrant and it is estimated that higher winds may still 
exist in this quadrant of Theta. For this reason, the latest 
intensity estimate is only adjusted downward to 50 kt for this 
advisory.

Theta continues to track east at 090/12 kt as the system remains 
steered by flow along the north side of a mid-level ridge. This 
ridge is forecast to gradually weaken over the next 24-36 h and 
Theta is forecast to bend to the east-southeast as the cyclone 
becomes more influenced by mid-level northerly flow associated with 
an upstream ridge building to the northwest. After 36 h, Theta is 
expected to slow down significantly as it becomes a shallow cyclone 
in light low-level flow. Finally, low-level southerly flow ahead of 
a mid-latitude cyclone is forecast to steer Theta's remnant low 
northeastward by the end of the forecast. The track guidance this 
cycle has shifted a bit southward for the first part of the 
forecast, and the official NHC track forecast has been adjusted 
slightly further south, close to the reliable ICVN consensus. 

Thus far, Theta has been struggling to produce deep convection that 
has successfully wrapped around its center. While Vertical Wind 
Shear is forecast to decrease per ECMWF-SHIPS guidance over the next 
12-24 h, it remains to be seen if the current degree of instability 
is enough for Theta to take advantage of the more conducive wind 
environment. Thereafter, Vertical Wind Shear increases sharply from 
the north, importing a much more stable environment over Theta.  For 
now, the latest NHC intensity forecast maintains the current 50 kt 
intensity over the next 24 h with weakening forecasted thereafter, 
in general agreement with the latest intensity guidance.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  13/0300Z 31.7N  26.0W   50 KT  60 MPH
 12H  13/1200Z 31.7N  24.2W   50 KT  60 MPH
 24H  14/0000Z 31.4N  22.1W   50 KT  60 MPH
 36H  14/1200Z 31.0N  20.4W   45 KT  50 MPH
 48H  15/0000Z 30.8N  19.2W   40 KT  45 MPH
 60H  15/1200Z 30.8N  18.6W   30 KT  35 MPH
 72H  16/0000Z 31.2N  18.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  17/0000Z 34.3N  18.2W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  18/0000Z...DISSIPATED
 
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Forecaster Papin/Cangialosi
 
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