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Subtropical Storm Theta Discussion Number   3
NWS National Hurricane Center Miami FL       AL302020
300 PM GMT Tue Nov 10 2020
 
Theta continues to exhibit a mix of tropical and subtropical 
characteristics. The cyclone has a fairly compact radius of maximum 
winds with a central dense overcast over the northern portion of the 
circulation. However, there is a strong subtropical jet located just 
to the south of Theta, and strong upper-level winds in the 
surrounding environment in the presence of an upper trough. Based on 
this inconclusive data, Theta is being maintained as a subtropical 
storm for this advisory. An ASCAT-B overpass this morning revealed 
50-kt winds in the northwest and southwest quadrants, with several 
55-60 kt wind vectors, some of those vectors outside of the deep 
convection making them more believable. Based on this, the initial 
advisory intensity has been set to 60 kt.
 
The storm is moving just north of due east, or 085/13 kt. Theta 
should continue to be steered eastward to east-northeastward during 
the next several days on the north side of a mid-level ridge.  This 
motion should take the cyclone across the subtropical eastern 
Atlantic throughout the forecast period.  The latest model guidance 
is a little faster and slightly north of the previous forecast 
track, and so the latest NHC forecast has been adjusted slightly as 
well. 
 
Theta is still expected to transition to a tropical storm later 
today as it separates from the upper-level trough.  Although Theta 
will be tracking over progressively cooler SSTs and within moderate 
wind shear conditions, the air mass is expected to remain unstable 
for the next couple of days, which should be supportive of deep 
convection. Therefore, little change is strength is indicated during 
that time. Some weakening is anticipated later in the forecast 
period as the airmass becomes more stable. The NHC intensity 
forecast is higher than the previous one primarily due to the higher 
initial intensity, and is near the IVCN and HCCA consensus models. 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  10/1500Z 29.0N  37.4W   60 KT  70 MPH
 12H  11/0000Z 29.1N  35.7W   60 KT  70 MPH
 24H  11/1200Z 29.7N  33.4W   60 KT  70 MPH
 36H  12/0000Z 30.4N  31.3W   55 KT  65 MPH
 48H  12/1200Z 31.1N  28.7W   55 KT  65 MPH
 60H  13/0000Z 31.7N  26.0W   50 KT  60 MPH
 72H  13/1200Z 32.2N  23.7W   45 KT  50 MPH
 96H  14/1200Z 33.0N  19.5W   40 KT  45 MPH
120H  15/1200Z 34.3N  17.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
 
$$
Forecaster Latto
 
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