[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 130252
TCDAT5

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

$$
Forecaster Papin/Cangialosi
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