000
WTNT45 KNHC 151432
TCDAT5

Post-Tropical Cyclone Theta Discussion Number  23
NWS National Hurricane Center Miami FL       AL302020
300 PM GMT Sun Nov 15 2020

Theta has run out of theta-e.  The cyclone has been without 
significant deep convection for many hours now and has been 
gradually spinning down today. It no longer meets the qualifications 
of a tropical cyclone, so this is the last advisory.  The initial 
wind speed is set to 25 kt per the latest scatterometer pass.  

The low is meandering this morning.  It is expected to be picked up 
to the north-northeast by the next trough over the northeastern 
Atlantic, along with an increase in forward speed.  The remnants of 
Theta should gradually lose strength due to strong shear, very dry 
air and little instability before dissipating in a day or two. 

Additional information on this system can be found in High Seas
Forecasts issued by the UK Met Office under WMO header FQNT21 EGRR
and on the web at
metoffice.gov.uk/weather/specialist-forecasts/coast-and-sea/high-
seas-forecast/.

FORECAST POSITIONS AND MAX WINDS

INIT  15/1500Z 31.5N  18.2W   25 KT  30 MPH...POST-TROPICAL
 12H  16/0000Z 31.9N  18.1W   25 KT  30 MPH...POST-TROP/REMNT LOW
 24H  16/1200Z 33.7N  17.7W   20 KT  25 MPH...POST-TROP/REMNT LOW
 36H  17/0000Z 36.5N  16.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 48H  17/1200Z...DISSIPATED

$$
Forecaster Blake

000
WTNT45 KNHC 150837
TCDAT5

Tropical Depression Theta Discussion Number  22
NWS National Hurricane Center Miami FL       AL302020
900 AM GMT Sun Nov 15 2020

Theta is barely a tropical cyclone. The only remnants of deep
convection are a small area of warming cloud tops, located around 
90 n mi to the southeast of Theta's exposed center. The cyclone has
produced little central convection all day, so it is assumed that at
least slight weakening has occurred and the intensity is set at
30 kt. This also agrees with a blend of the latest Dvorak Final-T
and CI numbers from TAFB. If Theta does not redevelop substantial
inner-core convection soon, it will likely become a remnant low
later today.

The cyclone has slowed down and is moving eastward with an initial 
motion of 090/4 kt. A continued slow eastward track is expected 
today, before a ridge centered over northwestern Africa begins to 
steer the cyclone northward on Monday. Although Theta could continue 
to produce intermittent bursts of convection, no significant 
redevelopment is anticipated due to surrounding dry air and cool 
underlying SSTs. The cyclone is forecast to become a remnant low 
within 12 h and dissipate in 60 h. No major changes were made to the 
NHC track or intensity forecasts, both of which are based on the 
multi-model consensus aids.


FORECAST POSITIONS AND MAX WINDS

INIT  15/0900Z 31.8N  18.3W   30 KT  35 MPH
 12H  15/1800Z 31.9N  17.8W   30 KT  35 MPH...POST-TROP/REMNT LOW
 24H  16/0600Z 33.1N  17.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 36H  16/1800Z 35.5N  16.9W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  17/0600Z 39.0N  14.8W   20 KT  25 MPH...POST-TROP/REMNT LOW
 60H  17/1800Z...DISSIPATED

$
Forecaster Zelinsky

000
WTNT45 KNHC 132038
TCDAT5

Tropical Storm Theta Discussion Number  16
NWS National Hurricane Center Miami FL       AL302020
900 PM GMT Fri Nov 13 2020

Theta appears to be holding its own still, with a large curved band 
feature characterizing the bulk of the deep convection, and a 
smaller area of convection intermittently developing over the 
center. Like yesterday, there has been a lack of observational data 
over the system's core since last night. However, since Theta's 
organization has not appeared to change much since that time, the 
initial intensity is being kept at a somewhat uncertain 50 kt.

Theta is forecast to change little in intensity into tonight as the 
cyclone continues moving in a relatively low shear zone associated 
with a mid- to upper-level trough axis.  By tomorrow, strong 
northerly shear is forecast to begin impacting the system while 
stable air gets entrained into its circulation.  As a result, Theta 
is expected to spin down over the weekend, degenerate to a remnant 
low on Sunday, and dissipate by the middle of next week.

Theta is moving eastward at around 9 kt, steered by a mid-level 
ridge extending westward from west Africa to the eastern tropical 
Atlantic. A turn to the east-southeast along with a gradual slowing 
of the forward motion is expected overnight and continuing through 
the weekend as the ridge weakens, and mid- to upper level northerly 
winds impart on the cyclone. Early next week, what remains of Theta 
are expected to turn northward and then accelerate northeastward as 
a mid-latitude cyclone passes to the north of the region.  The NHC 
forecast is little changed from the previous one and lies near the 
various consensus aids. On the forecast track, the center of Theta 
is forecast to track very near the westernmost Canary Islands. 
However, the system is forecast to weaken to a remnant low before 
reaching those islands. 


FORECAST POSITIONS AND MAX WINDS

INIT  13/2100Z 31.9N  22.6W   50 KT  60 MPH
 12H  14/0600Z 31.7N  21.0W   50 KT  60 MPH
 24H  14/1800Z 31.4N  19.2W   45 KT  50 MPH
 36H  15/0600Z 31.3N  18.2W   40 KT  45 MPH
 48H  15/1800Z 31.7N  17.7W   30 KT  35 MPH...POST-TROP/REMNT LOW
 60H  16/0600Z 32.5N  17.7W   30 KT  35 MPH...POST-TROP/REMNT LOW
 72H  16/1800Z 34.4N  17.3W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  17/1800Z 39.2N  12.8W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  18/1800Z...DISSIPATED

$$
Forecaster Latto

000
WTNT45 KNHC 120849
TCDAT5

Tropical Storm Theta Discussion Number  10
NWS National Hurricane Center Miami FL       AL302020
900 AM GMT Thu Nov 12 2020

Theta currently is comprised of a large swirl of low- to mid-level 
clouds with no convection near the center.  However, a band of 
convection is wrapped about three-quarters of the way around the 
center at a distance of about 200 n mi in the eastern semicircle 
and 100 n mi in the western semicircle.  Overall, the cyclone has 
somewhat of a subtropical appearance at this time.  Since there 
has been no data from the cyclone's core region since the last 
scatterometer pass, the initial intensity is held at 55 kt.  

The storm continued to jog a little to the left since the last 
advisory, but the last few satellite images suggest a more eastward 
motion has resumed.  The initial motion is a somewhat uncertain 
060/10.  For the next 24 h or so, Theta is expected to continue to 
move east-northeastward as it rounds the north side of a mid-level 
ridge centered over the Cabo Verde islands.  An eastward to 
east-southeastward motion is expected from 24-72 h as the mid-level 
ridge to the south weakens and mid- to upper-level northerly flow 
moves over the cyclone.  After that time, Theta or its remnants is 
expected to be steered northeastward in the low-level flow to the 
southeast of a deep-layer mid-latitude cyclone over the 
northeastern Atlantic.  The new forecast track is adjusted north of 
the previous track based on the initial position and motion, and it 
lies near the various consensus models.

Theta is forecast to change little in intensity during the next 36 
h or so as it moves into the light shear area near an upper-level 
trough axis.  After that time, the trough moves south of the 
cyclone, and strong northerly vertical shear should occur along 
with the entrainment of stable air.  This combination should cause 
Theta to quickly weaken, and the intensity forecast calls for the 
system to decay to a remnant low pressure area by 96 h.  The new 
intensity forecast has only minor adjustments from the old 
forecast, and it lies a little above the intensity consensus.


FORECAST POSITIONS AND MAX WINDS

INIT  12/0900Z 31.7N  30.2W   55 KT  65 MPH
 12H  12/1800Z 32.0N  28.5W   55 KT  65 MPH
 24H  13/0600Z 32.3N  26.2W   55 KT  65 MPH
 36H  13/1800Z 32.3N  24.0W   55 KT  65 MPH
 48H  14/0600Z 32.0N  22.1W   50 KT  60 MPH
 60H  14/1800Z 31.7N  20.8W   40 KT  45 MPH
 72H  15/0600Z 31.6N  20.1W   35 KT  40 MPH
 96H  16/0600Z 33.0N  19.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  17/0600Z 37.0N  18.0W   30 KT  35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Beven

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