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Tropical Storm Theta Discussion Number   8
NWS National Hurricane Center Miami FL       AL302020
900 PM GMT Wed Nov 11 2020
 
The deep convection associated with Theta has been trying to wrap 
around the cyclone's low-level center today, and the system consists 
of a large curved band feature with clouds tops as cold as -65 
degrees C. There was no complete sampling of the cyclone's 
circulation by the scatterometers today. However, a partial ASCAT-C 
overpass this morning showed that 40-45 kt winds were occurring in 
the eastern semicircle. This portion of the circulation has 
previously been the weaker portion of Theta, which suggests some 
higher winds could be occurring in the western semicircle. 
Therefore, the initial intensity is being kept at a somewhat 
uncertain 50 kt. 
 
Theta appears to be holding its own in an environment of strong 
southwesterly shear and over relatively cool water temperatures of 
about 24 degrees C, within a favorable unstable atmosphere. The 
cyclone will be traversing over progressively cooler waters over the 
next couple of days, and the shear is expected to only abate 
slightly. These somewhat counteracting factors should either allow 
Theta to maintain its intensity or slowly weaken during that time. 
Over the weekend, the upper-level winds are expected to increase 
and shift out of the north, and force more stable air across the 
cyclone. This should cause the convection to become displaced to the 
south of the center and gradually dissipate. The GFS/CMC/ECMWF 
simulated satellite imagery all indicate that the system should 
degenerate to a remnant low by 96 h. The latest NHC intensity 
forecast is similar to the previous one, and remains near the 
various multimodel consensus aids. 
 
The storm is moving east-northeastward at around 11 kt, steered by 
mid-latitude westerlies to the north of a mid-level ridge. This 
steering pattern is expected to remain in place for the next couple 
of days. Model guidance is trending slower over the weekend, as they 
are indicating that the ridge will weaken at around the same time 
that the shear vector becomes northerly. This would cause the 
cyclone to slow its forward motion and turn to the right, which is 
now indicated in the official forecast. However, the latest NHC 
track remains a little north of the consensus track guidance during 
that time frame. By the end of the forecast period, an approaching 
mid-latitude trough and associated front should pick up what remains 
of Theta and begin to accelerate it to the northeast. 

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  11/2100Z 30.5N  31.9W   50 KT  60 MPH
 12H  12/0600Z 31.1N  30.2W   50 KT  60 MPH
 24H  12/1800Z 31.5N  27.8W   50 KT  60 MPH
 36H  13/0600Z 31.9N  25.4W   45 KT  50 MPH
 48H  13/1800Z 32.1N  23.5W   45 KT  50 MPH
 60H  14/0600Z 32.0N  22.3W   45 KT  50 MPH
 72H  14/1800Z 31.8N  21.3W   40 KT  45 MPH
 96H  15/1800Z 31.7N  19.7W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  16/1800Z 35.1N  18.2W   30 KT  35 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Latto
 
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