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Tropical Storm Theta Discussion Number   7
NWS National Hurricane Center Miami FL       AL302020
300 PM GMT Wed Nov 11 2020
 
Theta's center continues to be devoid of deep convection, with the 
convective mass located primarily to the north of the center due to 
strong shear. A recent partial ASCAT overpass showed a slight 
decrease in the winds over the eastern semicircle. However, the pass 
did not sample the western portion of the circulation which has 
previously had the strongest winds. Based on the slightly lower 
ASCAT values, and the assumption that the rest of the vortex has 
spun down slightly due to the lack of convection over the center, 
the initial intensity is decreased to 50 kt.
 
Theta is moving east-northeastward at 9 kt, steered by the southern 
part of the mid-latitude westerlies to the north of a mid-level 
ridge. This steering pattern is expected to remain in place through 
much of the weekend. By early next week, the ridge is forecast 
weaken ahead of an approaching mid-latitude trough. This would cause 
the cyclone to slow its forward motion temporarily before it gets 
picked up by the trough. The latest NHC forecast is near the 
previous one through 72 h, and is a little slower during days 4-5 
due to the slowing of the guidance. This latest forecast is very 
near the clustered track consensus models. 

Despite the strong shear and cool water temperatures, the 
instability aloft should continue to support deep convection for at 
least the next few days. The shear is forecast to lessen somewhat 
in a day or so, but will still be relatively strong. Since the 
cyclone has been weakening slowly in the current environment, it is 
anticipated that the pace of weakening may lessen during the next 
few days with the decrease in shear. Beyond that time, the 
upper-level winds are forecast to become more northerly, and 
at about the same time the instability is forecast to decrease. 
These factors should cause any remaining convection to dissipate, 
with Theta likely becoming post-tropical by day 5. The latest 
NHC intensity forecast was adjusted slightly downward from the 
previous one mainly due to the lower initial intensity and is near 
the IVCN and HCCA consensus model forecasts.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  11/1500Z 29.8N  33.3W   50 KT  60 MPH
 12H  12/0000Z 30.3N  31.9W   50 KT  60 MPH
 24H  12/1200Z 30.7N  29.7W   45 KT  50 MPH
 36H  13/0000Z 31.1N  27.3W   45 KT  50 MPH
 48H  13/1200Z 31.5N  25.1W   45 KT  50 MPH
 60H  14/0000Z 31.8N  23.2W   45 KT  50 MPH
 72H  14/1200Z 31.9N  22.0W   40 KT  45 MPH
 96H  15/1200Z 32.2N  20.6W   35 KT  40 MPH
120H  16/1200Z 34.7N  19.2W   35 KT  40 MPH...POST-TROPICAL
 
$$
Forecaster Latto
 
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