Tropical Storm Theta Forecast Discussion


000
WTNT45 KNHC 102037
TCDAT5

Tropical Storm Theta Discussion Number   4
NWS National Hurricane Center Miami FL       AL302020
900 PM GMT Tue Nov 10 2020

A central dense overcast has persisted near the center of Theta 
since yesterday, and although the clouds tops have warmed over the 
past several hours there remains a distinct curved band feature 
over the northern portion of the circulation. Water vapor imagery 
shows the mid- upper-level trough that was over the Azores is 
beginning to leave the cyclone behind. Based on these factors, and 
the earlier indications of a compact radius of maximum winds, it 
appears that Theta has completed a transition to a tropical 
cyclone. Even though the clouds tops have recently warmed, the 
overall structure of Theta has not degraded by much since the 
previous advisory. Therefore, the initial intensity is being held 
at 60 kt. 

The storm is moving 075/12 kt around the north side of a mid-level 
ridge. This feature should continue to steer Theta in a generally 
east-northeastward motion for the next few days. Late in the 
forecast period, the ridge will begin to weaken as another trough 
approaches from the northwest. This should cause the cyclone to slow 
its forward motion and begin to turn to the northeast. The latest 
model guidance has once again slowed down and the new NHC track 
forecast now lies between the previous one and the various consensus 
models.

Although Theta will be moving over progressively cooler SSTs and 
within moderate wind shear conditions, the air mass is expected to 
remain unstable for the next day or so, 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. By the end 
of the 5-day forecast period, the combination of the cooler waters 
and an approaching trough should result in extratropical transition. 
The NHC intensity forecast has changed little from the previous one 
and remains near the IVCN and HCCA consensus models.

FORECAST POSITIONS AND MAX WINDS

INIT  10/2100Z 29.4N  36.2W   60 KT  70 MPH
 12H  11/0600Z 29.8N  34.7W   60 KT  70 MPH
 24H  11/1800Z 30.3N  32.8W   55 KT  65 MPH
 36H  12/0600Z 30.8N  30.5W   55 KT  65 MPH
 48H  12/1800Z 31.5N  28.0W   50 KT  60 MPH
 60H  13/0600Z 32.1N  25.7W   50 KT  60 MPH
 72H  13/1800Z 32.6N  23.8W   45 KT  50 MPH
 96H  14/1800Z 33.2N  20.5W   40 KT  45 MPH
120H  15/1800Z 34.4N  19.0W   35 KT  40 MPH...POST-TROP/EXTRATROP

$$
Forecaster Latto

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