ATL: THETA - Advisories

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Re: ATL: THETA - Advisories

#21 Postby cycloneye » Sat Nov 14, 2020 3:37 pm

Tropical Storm Theta Discussion Number 20
NWS National Hurricane Center Miami FL AL302020
900 PM GMT Sat Nov 14 2020

A persistent band of deep convection to the southeast of Theta's
center continues to keep it classifiable as a tropical cyclone, with
the edge of the convection at one point today reaching within 60 n
mi of the center of the cyclone. Over the past couple of hours this
convection has become farther displaced from Theta's center, as the
system gets blasted by over 40 kt of northerly shear. Since the
cyclone's appearance has changed little today, the initial
intensity is being held at 35 kt based off data from an ASCAT-A
overpass this morning. Very strong shear and dry air entrainment
should cause the deep convection to weaken and become even farther
displaced from the center tonight, with Theta anticipated to
degenerate into a remnant low by 12 h. The cyclone should also
weaken under this regime, and open into a trough by 72 h. The latest
NHC intensity forecast is unchanged from the previous one, and is in
good agreement with the intensity guidance.

Theta continues moving just south of due east, but now at a slower
pace of around 5 kt. A mid-level ridge located to the south of Theta
is weakening, which will result in a continued slow
east-southeastward motion through tonight. As Theta becomes a
shallow system on Sunday, the low-level flow is forecast to become
southwesterly, and this flow is expected to increase on Monday ahead
of an approaching cold front. This will cause Theta to turn to the
northeast by late Sunday and accelerate until it dissipates in a few
days. The latest NHC track forecast is similar to the previous one
and lies near the track consensus models.


FORECAST POSITIONS AND MAX WINDS

INIT 14/2100Z 31.7N 19.2W 35 KT 40 MPH
12H 15/0600Z 31.7N 18.3W 30 KT 35 MPH...POST-TROP/REMNT LOW
24H 15/1800Z 32.1N 17.5W 30 KT 35 MPH...POST-TROP/REMNT LOW
36H 16/0600Z 33.2N 17.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 16/1800Z 35.1N 16.4W 20 KT 25 MPH...POST-TROP/REMNT LOW
60H 17/0600Z 38.1N 14.7W 20 KT 25 MPH...POST-TROP/REMNT LOW
72H 17/1800Z...DISSIPATED

$$
Forecaster Latto
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Re: ATL: THETA - Advisories

#22 Postby cycloneye » Sat Nov 14, 2020 9:36 pm

Tropical Storm Theta Discussion Number 21
NWS National Hurricane Center Miami FL AL302020
300 AM GMT Sun Nov 15 2020

Theta remains a highly sheared but resilient tropical cyclone with
little change in its satellite appearance since the previous
advisory. A persistent band of deep convection to the southeast of
Theta remains within about 60 n mi of the storm center, despite a
hostile environment characterized by dry mid-level air and 40-50 kt
of northerly shear. Unfortunately, several scatterometer passes this
evening missed the core of the cyclone. Since the satellite
presentation is generally unchanged from earlier today, the initial
intensity is held at 35 kt, which is consistent with a T2.5 Dvorak
classification received from TAFB.

Strong northerly shear and continued dry air entrainment will
eventually take a toll on Theta, but recent satellite trends and the
latest GFS simulated satellite imagery suggest that the cyclone
could remain tropical a little longer than previously forecast. The
latest NHC intensity forecast keeps Theta as a 35-kt tropical storm
at 12 h before weakening it into a remnant low by 24 h. This follows
the consensus of the latest intensity guidance. Thereafter,
continued weakening is expected through its dissipation early next
week.

Theta is still moving eastward at around 4 kt. The cyclone should
begin turning northeastward later today, and then accelerate
north-northeastward on Monday as the shallow remnant low is steered
by a low-level ridge centered over northwestern Africa. The remains
of Theta are forecast to open up into a trough and dissipate by 60 h
ahead of an approaching cold front over the northeastern Atlantic.
The latest NHC track forecast is adjusted slightly to the left of
the previous one, which generally follows the latest track consensus
aids. On the forecast track, the remnant low of Theta is expected to
pass near the island of Madeira late Sunday night or early Monday.


FORECAST POSITIONS AND MAX WINDS

INIT 15/0300Z 31.7N 18.7W 35 KT 40 MPH
12H 15/1200Z 31.9N 18.0W 35 KT 40 MPH
24H 16/0000Z 32.6N 17.4W 30 KT 35 MPH...POST-TROP/REMNT LOW
36H 16/1200Z 34.2N 17.1W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 17/0000Z 36.7N 15.9W 20 KT 25 MPH...POST-TROP/REMNT LOW
60H 17/1200Z...DISSIPATED

$$
Forecaster Reinhart/Cangialosi
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Re: ATL: THETA - Advisories

#23 Postby cycloneye » Sun Nov 15, 2020 4:52 am

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
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Re: ATL: THETA - Advisories

#24 Postby cycloneye » Sun Nov 15, 2020 9:34 am

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

...THETA BECOMES A REMNANT LOW...
...THIS IS THE LAST ADVISORY...


SUMMARY OF 300 PM GMT...1500 UTC...INFORMATION
----------------------------------------------
LOCATION...31.5N 18.2W
ABOUT 670 MI...1080 KM SE OF THE AZORES
MAXIMUM SUSTAINED WINDS...30 MPH...45 KM/H
PRESENT MOVEMENT...N OR 360 DEGREES AT 2 MPH...4 KM/H
MINIMUM CENTRAL PRESSURE...1010 MB...29.83 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND OUTLOOK
----------------------
At 300 PM GMT (1500 UTC), the center of Post-Tropical Cyclone Theta
was located near latitude 31.5 North, longitude 18.2 West. The
post-tropical cyclone is moving toward the north near 2 mph (4 km/h)
and a faster north or north-northeast motion is forecast for a day
or two until the low dissipates.

Maximum sustained winds are near 30 mph (45 km/h) with higher gusts.
The low should gradually decay and dissipate by Tuesday.

The estimated minimum central pressure is 1010 mb (29.83 inches).


HAZARDS AFFECTING LAND
----------------------
None.


NEXT ADVISORY
-------------
This is the last public advisory issued by the National Hurricane
Center on this system. 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/.

$$
Forecaster Blake
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