EPAC: XAVIER - Post-Tropical

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cycloneye
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Re: EPAC: XAVIER - Tropical Storm

#21 Postby cycloneye » Mon Nov 05, 2018 9:36 am

Tropical Storm Xavier Discussion Number 12
NWS National Hurricane Center Miami FL EP252018
800 AM MST Mon Nov 05 2018

A burst of deep convection occurred over the low-level center
around the time of the last advisory, but that activity has again
been scoured off to the northeast due to 30 kt of southwesterly
shear. Satellite intensity estimates have not changed, and the
initial intensity remains 50 kt, which is very close to the latest
UW-CIMSS ADT and SATCON estimates. Xavier has been tenaciously
resisting the ill effects of shear for the time being. However,
the circulation will be moving westward toward a drier environment
where mid-level relative humidity values are 30-40 percent. In
theory, the combination of strong shear and drier air should put an
end to deep convection production, but relatively warm waters could
still allow the cyclone to produce intermittent bursts of shower and
thunderstorm activity over the next several days. Based on the
latest intensity guidance, no changes were made to the official
forecast, which continues to show Xavier becoming a remnant low in
48 hours and dissipating by day 4.

Caught within a break in the subtropical ridge, Xavier is only
creeping west-northwestward, or 295/3 kt. As deep convection
gradually dwindles near the cyclone, the shallower circulation is
expected to be steered westward to the south of a low-level ridge
stretching across northern Mexico and the Baja California
peninsula. The new NHC track forecast is nearly identical to the
previous one during the first 24 hours. After 24 hours, it has
been nudged southward toward the various consensus aids, continuing
the trend that was noted by the previous forecaster.

Even though Xavier is slowly moving away from the coast of Mexico,
inclement weather is still occurring near the coasts of Colima and
Jalisco, and tropical-storm-force winds could still be occurring
in that vicinity. Therefore, it's prudent to continue the Tropical
Storm Warning until we have confirmation that the strong winds have
shifted farther offshore.


FORECAST POSITIONS AND MAX WINDS

INIT 05/1500Z 18.5N 106.2W 50 KT 60 MPH
12H 06/0000Z 18.7N 107.0W 40 KT 45 MPH
24H 06/1200Z 18.9N 108.3W 35 KT 40 MPH
36H 07/0000Z 18.9N 109.7W 30 KT 35 MPH
48H 07/1200Z 18.8N 111.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 08/1200Z 18.5N 113.1W 20 KT 25 MPH...POST-TROP/REMNT LOW
96H 09/1200Z...DISSIPATED

$$
Forecaster Berg
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Re: EPAC: XAVIER - Tropical Storm

#22 Postby plasticup » Mon Nov 05, 2018 11:30 am

HurricaneRyan wrote:First X name storm in my lifetime . this is exciting!

You are <12 years old?
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Re: EPAC: XAVIER - Tropical Storm

#23 Postby tolakram » Mon Nov 05, 2018 12:55 pm

plasticup wrote:
HurricaneRyan wrote:First X name storm in my lifetime . this is exciting!

You are <12 years old?


I assumed he meant in the EPAC.
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Re: EPAC: XAVIER - Tropical Storm

#24 Postby cycloneye » Mon Nov 05, 2018 3:41 pm

Tropical Storm Xavier Discussion Number 13
NWS National Hurricane Center Miami FL EP252018
200 PM MST Mon Nov 05 2018

All of Xavier's deep convection dissipated around 1500 UTC, leaving
a swirl of low- to mid-level clouds with embedded shower activity.
The initial intensity is lowered to 45 kt based on a pair of recent
ASCAT passes over the circulation. Strong southwesterly shear and
the surrounding dry environment finally appear to have cut off the
production of deep convection, and although intermittent bursts of
thunderstorms are still possible, it is unlikely that the
circulation will be able to produce persistent organized
convection. Therefore, Xavier's degeneration into a remnant low
has been moved up by 24 hours in the official forecast, although it
is entirely possible that it could become a post-tropical low as
early as tonight. Xavier's winds are also expected to continue to
gradually diminish, likely falling below tropical-storm-force
overnight or early Tuesday. The remnant low should then dissipate
by day 4.

The initial motion is a little faster toward the west-northwest
(300 degrees) at 4 kt. A low-level ridge extending from northern
Mexico westward over the Pacific should drive the now-shallow
circulation west-northwestward to westward at a slightly faster
speed during the next few days. The new NHC track forecast has
been adjusted northward to account for recent motion trends, but it
otherwise lies through the middle of the guidance envelope, close
to the HCCA and Florida State Superensemble guidance.

FORECAST POSITIONS AND MAX WINDS

INIT 05/2100Z 19.0N 106.9W 45 KT 50 MPH
12H 06/0600Z 19.2N 107.6W 35 KT 40 MPH
24H 06/1800Z 19.3N 108.9W 30 KT 35 MPH...POST-TROP/REMNT LOW
36H 07/0600Z 19.3N 110.1W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 07/1800Z 19.1N 111.2W 20 KT 25 MPH...POST-TROP/REMNT LOW
72H 08/1800Z 19.0N 112.8W 15 KT 15 MPH...POST-TROP/REMNT LOW
96H 09/1800Z...DISSIPATED

$$
Forecaster Berg
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Re: EPAC: XAVIER - Post-Tropical

#25 Postby cycloneye » Mon Nov 05, 2018 9:58 pm

Post-Tropical Cyclone Xavier Discussion Number 14
NWS National Hurricane Center Miami FL EP252018
800 PM MST Mon Nov 05 2018

Deep convection has now remained absent in Xavier for about twelve
hours. Given the hostile southwesterly vertical shear, dry
mid-levels, and only lukewarm waters to be encountered by the system
during the next couple of days, it is unlikely that persistent deep
convection will make a comeback. Therefore, Xavier is now
considered to be a post-tropical cyclone and this is the last
advisory to be issued by the National Hurricane Center.

Despite the lack of thunderstorms, Xavier is showing a well-
pronounced, though small, low-level circulation in the last few
visible images. Peak winds in the system are around 40 kt, assuming
that some spindown has occurred since the 45 kt observed from the
ASCAT scatterometer several hours ago. Continued gradual weakening
is very likely and Xavier is anticipated to become a remnant low by
Tuesday night and dissipate in about three days.

The post-tropical cyclone is moving west-northwestward at around
5 kt. The system should turn toward the west or west-southwest
during the next couple of days until dissipation, under the
influence of a lower tropospheric ridge north of Xavier.

For additional information on the post-tropical cyclone, please see
High Seas Forecasts issued by the National Weather Service, under
AWIPS header NFDHSFEPI, WMO header FZPN02 KWBC, and on the web at
https://ocean.weather.gov/shtml/NFDHSFEPI.shtml.


FORECAST POSITIONS AND MAX WINDS

INIT 06/0300Z 19.1N 107.5W 40 KT 45 MPH...POST-TROPICAL
12H 06/1200Z 19.2N 108.5W 35 KT 40 MPH...POST-TROPICAL
24H 07/0000Z 19.3N 109.7W 30 KT 35 MPH...POST-TROP/REMNT LOW
36H 07/1200Z 19.2N 110.9W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 08/0000Z 19.1N 112.0W 20 KT 25 MPH...POST-TROP/REMNT LOW
72H 09/0000Z 18.8N 113.4W 15 KT 15 MPH...POST-TROP/REMNT LOW
96H 10/0000Z...DISSIPATED

$$
Forecaster Landsea
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Re: EPAC: XAVIER - Post-Tropical

#26 Postby galaxy401 » Tue Nov 06, 2018 10:02 am

After being very resilient to the shear, it completely collapsed very quickly! This the final storm of the season?
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Re: EPAC: XAVIER - Post-Tropical

#27 Postby 1900hurricane » Tue Nov 06, 2018 10:45 am

What a cool looking remnant low.

Image

Image
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