[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 140238
TCDAT5

Tropical Storm Theta Discussion Number  17
NWS National Hurricane Center Miami FL       AL302020
300 AM GMT Sat Nov 14 2020

Theta is beginning to show signs of weakening tonight. Infrared
cloud top temperatures have warmed during the past several hours
within the weakening convective band that curves around the
northeastern semicircle of the storm. A partial 22 UTC ASCAT-B
overpass indicates that Theta maintains a fairly symmetric low-level
wind field, with 35-40 kt winds in the eastern semicircle of the
storm. Therefore, the initial intensity is lowered to 45 kt with
this advisory, which is consistent with UW-CIMSS objective current
intensity estimates but slightly higher than the T2.5 subjective
Dvorak classification from TAFB.

Theta will encounter increasingly hostile environmental conditions
over the next couple of days. The NHC intensity forecast calls for
steady weakening through the weekend, as strong northerly wind shear
and cool sea surface temperatures will likely inhibit the storm from
sustaining convection near its center. This forecast closely follows
the corrected consensus aid HCCA. Theta is expected to weaken to a
tropical depression within 36 h and degenerate into a remnant low by
48 h, although the GFS simulated satellite imagery suggests this
could occur even sooner than forecast. The remnant low should
dissipate by the middle of next week.

Theta is still moving eastward at around 9 kt around the northern
periphery of a mid-level ridge that extends from western Africa
across the eastern tropical Atlantic. An eastward or
east-southeastward motion with a gradual decrease in forward speed
is expected during the next 24-36 h. As the storm spins down and
becomes a more shallow circulation, the remains of Theta will turn
northward and then accelerate northeastward ahead of a mid-latitude
cyclone and associated frontal system that will cross the
northeastern Atlantic. The NHC track forecast lies close to the
previous one and near the center of the guidance envelope. On the
forecast track, the center of Theta is expected to pass northwest of
the Canary Islands this weekend, then move near Madeira Island early
Monday as a weak remnant low.


FORECAST POSITIONS AND MAX WINDS

INIT  14/0300Z 31.9N  21.6W   45 KT  50 MPH
 12H  14/1200Z 31.8N  20.2W   40 KT  45 MPH
 24H  15/0000Z 31.6N  18.6W   35 KT  40 MPH
 36H  15/1200Z 31.7N  17.8W   30 KT  35 MPH
 48H  16/0000Z 32.3N  17.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 60H  16/1200Z 33.7N  17.3W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  17/0000Z 35.9N  16.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  18/0000Z...DISSIPATED

$$
Forecaster Reinhart/Cangialosi
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