Tropical Storm Sebastien

[PaulyFromPlattsburgh]

Sebastien has formed in the open Atlantic.

[Hurricane Agnes]

Was trying to post earlier but there were apparently some issues with Amwx....

5 am update on Sebastien -

Quote

000
WTNT35 KNHC 200836
TCPAT5

BULLETIN
Tropical Storm Sebastien Advisory Number   4
NWS National Hurricane Center Miami FL       AL202019
500 AM AST Wed Nov 20 2019

...SEBASTIEN A LITTLE STRONGER...


SUMMARY OF 500 AM AST...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...21.0N 61.0W
ABOUT 235 MI...380 KM NE OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...NW OR 305 DEGREES AT 8 MPH...13 KM/H
MINIMUM CENTRAL PRESSURE...1002 MB...29.59 INCHES


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


DISCUSSION AND OUTLOOK
----------------------
At 500 AM AST (0900 UTC), the center of Tropical Storm Sebastien was
located near latitude 21.0 North, longitude 61.0 West. Sebastien is
moving toward the northwest near 8 mph (13 km/h). A turn to the
north-northwest and north is expected later today. A turn toward
the northeast with an increase in forward speed is expected tonight
and Thursday.

Maximum sustained winds have increased to near 50 mph (85 km/h)
with higher gusts. Some strengthening is forecast during the next
48 hours. Sebastien is expected to become an extratropical cyclone
in a couple of days and be absorbed by a cold front on Friday.

Tropical-storm-force winds extend outward up to 150 miles (240 km)
from the center.

The estimated minimum central pressure is 1002 mb (29.59 inches).


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


NEXT ADVISORY
-------------
Next complete advisory at 1100 AM AST.

$$
Forecaster Brown

Quote

426 
WTNT45 KNHC 200837
TCDAT5

Tropical Storm Sebastien Discussion Number   4
NWS National Hurricane Center Miami FL       AL202019
500 AM AST Wed Nov 20 2019

Deep convection developed closer to the center of Sebastien
around the time of the previous advisory, but northwesterly shear
and dry air have caused it to wane within the past hour or two.  A
late arriving ASCAT-C overpass revealed peak winds a little above
40 kt. Given the typical undersampling of that instrument, the
initial intensity has been raised to 45 kt. The shear and dry air
are expected to keep Sebastien's intensity in check today, but by
tonight the upper-level divergence is forecast to increase while the
storm motion and shear vector line up.  This is expected to allow
for some strengthening and nearly all of the intensity guidance and
global models predict deepening.  The new intensity forecast is
again similar to the previous advisory and lies between the lower
statistical guidance and the more aggressive dynamical models.

Sebastien appears to have turned northwestward with an initial
motion of 305/7 kt. A turn to the north should occur later today,
and then a northeastward motion is predicted to begin by Wednesday
night as the storm is picked up by a deep layer trough moving
eastward across the western Atlantic.  The track guidance is in
agreement on this overall scenario but there are some significant
differences in how quickly Sebastien accelerates northeastward.  The
GFS, HWRF, and HMON show the storm recurving quickly ahead of
the trough while the ECMWF is quite a bit slower.  The NHC track is
a little slower than the previous forecast, but remains close to the
various consensus aids and the latest UKMET ensemble mean.

FORECAST POSITIONS AND MAX WINDS

INIT  20/0900Z 21.0N  61.0W   45 KT  50 MPH
 12H  20/1800Z 21.7N  61.5W   45 KT  50 MPH
 24H  21/0600Z 23.2N  60.8W   50 KT  60 MPH
 36H  21/1800Z 25.3N  58.6W   55 KT  65 MPH
 48H  22/0600Z 28.7N  54.4W   55 KT  65 MPH...POST-TROP/EXTRATROP
 72H  23/0600Z...DISSIPATED

$$
Forecaster Brown

 

[Hurricane Agnes]

5 pm update (now moving N and slowed a bit) -

Quote

667 
WTNT35 KNHC 202036
TCPAT5

BULLETIN
Tropical Storm Sebastien Advisory Number   6
NWS National Hurricane Center Miami FL       AL202019
500 PM AST Wed Nov 20 2019

...SEBASTIEN MAKES ITS NORTHWARD TURN...
...EXPECTED TO BEGIN INTENSIFYING SOON...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...21.7N 61.5W
ABOUT 265 MI...425 KM NNE OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...N OR 360 DEGREES AT 6 MPH...9 KM/H
MINIMUM CENTRAL PRESSURE...1002 MB...29.59 INCHES


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


DISCUSSION AND OUTLOOK
----------------------
At 500 PM AST (2100 UTC), the center of Tropical Storm Sebastien was
located near latitude 21.7 North, longitude 61.5 West. Sebastien is
moving toward the north near 6 mph (9 km/h). A turn to the northeast
with an increase in forward speed is expected tonight and Thursday.

Maximum sustained winds are near 50 mph (85 km/h) with higher gusts.
Some strengthening is forecast during the next 48 hours. Sebastien
is expected to become an extratropical cyclone in a couple of days
and be absorbed by a cold front on Friday.

Tropical-storm-force winds extend outward up to 160 miles (260 km)
from the center.

The estimated minimum central pressure is 1002 mb (29.59 inches).


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


NEXT ADVISORY
-------------
Next complete advisory at 1100 PM AST.

$$
Forecaster Latto

Quote

374 
WTNT45 KNHC 202037
TCDAT5

Tropical Storm Sebastien Discussion Number   6
NWS National Hurricane Center Miami FL       AL202019
500 PM AST Wed Nov 20 2019

Sebastien has changed little in organization today, with
northwesterly shear displacing the deep convection to the southeast
of an exposed low-level center. An ASCAT-C overpass late this
morning sampled peak winds of 41 kt, and so the initial advisory
intensity will remain 45 kt due to the assumption of undersampling
by the scatterometer.

Sebastien made its anticipated turn to the north earlier today, and
the current motion is now 360/05 kt. The cyclone should turn to the
northeast tonight and begin to accelerate as it gets embedded in
increasing southwesterly flow ahead of an approaching cold front and
associated mid- to upper- level trough. The official forecast track
is near the previous one through 24 hours, and a little slower and
to the south of it beyond that time due to a shift in the model
guidance.

The approaching trough should provide a diffluent environment aloft
over Sebastien beginning tonight and persisting until the system
makes the transition to an extratropical cyclone in a couple of
days. This is expected to result in some intensification over the
next day or so. Once extratropical, the cyclone should gradually
become absorbed into a frontal zone through the end of the week. The
official forecast is changed little from the previous one, and is
near the IVCN consensus.


FORECAST POSITIONS AND MAX WINDS

INIT  20/2100Z 21.7N  61.5W   45 KT  50 MPH
 12H  21/0600Z 22.7N  61.0W   50 KT  60 MPH
 24H  21/1800Z 24.5N  59.0W   60 KT  70 MPH
 36H  22/0600Z 27.2N  55.5W   60 KT  70 MPH
 48H  22/1800Z 30.0N  51.4W   60 KT  70 MPH...POST-TROP/EXTRATROP
 72H  23/1800Z...DISSIPATED

$$
Forecaster Latto

 

[Hurricane Agnes]

Better late than never but a 5 pm Sat. update (although it has strengthened over the past couple days, it is expected to become post-tropical tomorrow and dissipate next week) -

Quote

622 
WTNT35 KNHC 232037
TCPAT5

BULLETIN
Tropical Storm Sebastien Advisory Number  18
NWS National Hurricane Center Miami FL       AL202019
500 PM AST Sat Nov 23 2019

...SEBASTIEN GALLOPING QUICKLY NORTHEASTWARD...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...32.4N 45.4W
ABOUT 1105 MI...1780 KM WSW OF THE AZORES
MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/H
PRESENT MOVEMENT...NE OR 45 DEGREES AT 28 MPH...44 KM/H
MINIMUM CENTRAL PRESSURE...997 MB...29.44 INCHES


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


DISCUSSION AND OUTLOOK
----------------------
At 500 PM AST (2100 UTC), the center of Tropical Storm Sebastien was
located near latitude 32.4 North, longitude 45.4 West. Sebastien is
moving quickly toward the northeast near 28 mph (44 km/h). A fast
northeastward motion is expected for the next couple of days.

Maximum sustained winds are near 65 mph (100 km/h) with higher
gusts. Little change in the maximum winds is expected during the
next couple of days. Sebastien is forecast to become post-tropical
on Sunday and dissipate early next week.

Tropical-storm-force winds extend outward up to 90 miles (150 km)
from the center.

The estimated minimum central pressure is 997 mb (29.44 inches).


HAZARDS AFFECTING LAND
----------------------
WIND AND RAIN: Regardless of its status, Sebastien or its remnants
are expected to bring gusty winds and rain to the Azores beginning
Sunday. Please see products issued by the Portuguese Institute for
the Sea and the Atmosphere (IPMA) for more information.

SURF:  Swells generated by Sebastien are expected to reach the
Azores early next week. These swells are likely to cause
life-threatening surf and rip current conditions.


NEXT ADVISORY
-------------
Next complete advisory at 1100 PM AST.

$$
Forecaster Zelinsky

Quote

000
WTNT45 KNHC 232038
TCDAT5

Tropical Storm Sebastien Discussion Number  18
NWS National Hurricane Center Miami FL       AL202019
500 PM AST Sat Nov 23 2019

Sebastien's cloud pattern is beginning to resemble that of an
extratropical cyclone, with a shield of moderately cold cloud tops
extending well to the north of the cyclone's surface center. That
said, Sebastien is still producing enough convection near its center
to be considered a tropical cyclone for now. ASCAT-B data that
arrived shortly after the last advisory was issued had support for
55 kt and that is the basis for the initial intensity. The ASCAT
data also showed that the surface wind circulation of Sebastien is
elongated but still closed.

Sebastien is accelerating northeastward, with an initial motion of
045/26 kt. Most of the 12Z models show a significantly faster
northeastward track for the tropical storm and the official forecast
has been adjusted accordingly. However, the NHC forecast is slower
than the model consensus and additional large changes may be
required in the next advisory. Confidence in the track forecast
remains low due to the continued lack of run-to-run consistency
amongst the models. With regard to intensity, a majority of the
guidance calls for little change in strength since it seems that
baroclinic forcing will at least offset the negative influences of
decreasing SSTs and high shear during the next day or two. The NHC
intensity forecast is very near the consensus. Cyclone phase-space
diagrams derived from the GFS and ECMWF indicate that extratropical
transition could occur by Sunday afternoon, but the NHC forecast is
slightly more conservative. The reality is that Sebastien could
become extratropical or open into a trough at nearly any time
between this evening and early next week.

Sebastien or its remnants are expected to bring gusty winds and
rain to the Azores beginning on Sunday. Please see products issued
by the Portuguese Institute for the Sea and the Atmosphere (IPMA)
for more information.


FORECAST POSITIONS AND MAX WINDS

INIT  23/2100Z 32.4N  45.4W   55 KT  65 MPH
 12H  24/0600Z 35.0N  41.5W   55 KT  65 MPH
 24H  24/1800Z 37.8N  35.3W   55 KT  65 MPH
 36H  25/0600Z 40.9N  27.6W   55 KT  65 MPH...POST-TROP/EXTRATROP
 48H  25/1800Z 44.8N  19.3W   50 KT  60 MPH...POST-TROP/EXTRATROP
 72H  26/1800Z...DISSIPATED

$$
Forecaster Zelinsky

 

[Hurricane Agnes]

5 am update and it continues to strengthen (plus a slight delay in prog for it going post-tropical) -

Quote

000
WTNT35 KNHC 240846
TCPAT5

BULLETIN
Tropical Storm Sebastien Advisory Number  20
NWS National Hurricane Center Miami FL       AL202019
500 AM AST Sun Nov 24 2019

...SEBASTIEN ACCELERATING NORTHEASTWARD TOWARD THE WESTERN AZORES...
...FORECAST TO BECOME POST-TROPICAL OVER THE NEXT DAY OR SO...


SUMMARY OF 500 AM AST...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...36.0N 40.0W
ABOUT 730 MI...1175 KM W OF THE AZORES
MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/H
PRESENT MOVEMENT...NE OR 50 DEGREES AT 33 MPH...54 KM/H
MINIMUM CENTRAL PRESSURE...994 MB...29.36 INCHES


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

Interests in the Azores should monitor the progress of Sebastien.


DISCUSSION AND OUTLOOK
----------------------
At 500 AM AST (0900 UTC), the center of Tropical Storm Sebastien was
located near latitude 36.0 North, longitude 40.0 West.  Sebastien is
moving faster toward the northeast near 33 mph (54 km/h), and an
additional increase in speed toward the northeast is expected
during the next day or so.  On the forecast track, the center of
Sebastien will pass near the western Azores tonight.

Maximum sustained winds are near 65 mph (100 km/h) with higher
gusts.  A slow decrease in the maximum winds is expected
during the next couple of days.  Sebastien is forecast to become
post-tropical tonight and then merge with another weather system
over the northeastern Atlantic on Tuesday.

Tropical-storm-force winds extend outward up to 115 miles (185 km)
from the center.

The estimated minimum central pressure is 994 mb (29.36 inches).


HAZARDS AFFECTING LAND
----------------------
WIND AND RAIN:  Regardless of its status, Sebastien or its remnants
are expected to bring gusty winds and rain to the Azores beginning
later today.  Please see products issued by the Portuguese Institute
for the Sea and the Atmosphere (IPMA) for more information.

SURF:  Swells generated by Sebastien are expected to reach the
Azores later today and tonight.  These swells are likely to cause
life-threatening surf and rip current conditions.


NEXT ADVISORY
-------------
Next complete advisory at 1100 AM AST.

$$
Forecaster Berg

Quote

000
WTNT45 KNHC 240847
TCDAT5

Tropical Storm Sebastien Discussion Number  20
NWS National Hurricane Center Miami FL       AL202019
500 AM AST Sun Nov 24 2019

Sebastien is on the slow boat to becoming fully extratropical.
Just within the past few hours, the cyclone has taken on an
appearance more resembling a subtropical cyclone, with all of its
deep convection located in a band to the north of the center and it
being co-located with an upper-level shortwave trough.  Based on
Sebastien's evolving structure, TAFB provided a subtropical
classification of ST3.5.  Combining this estimate with the most
recent ADT and SATCON estimates, the initial intensity remains 55
kt.

Since Sebastien's extratropical transition has been so drawn out,
it's difficult to pinpoint exactly when the process will be
complete.  Phase-space diagrams from the GFS and ECMWF models
indicate that the cyclone will be deep cold core within the next
6-12 hours.  However, these models keep the low-level vortex
separate from a second upstream upper-level trough for the next 30
hours, and they also keep deep convection going (in simulated
satellite imagery) near but to the north of the center for that same
amount of time.  Because of deep-layer shear around 40 kt and sea
surface temperatures near 20C, the official forecast continues to
show extratropical transition complete by 24 hours, but that
forecast should be considered with a margin of error of plus or
minus 12 hours.  Regardless of its status, Sebastien is forecast to
only gradually lose strength over the next 48 hours and is likely to
bring gusty winds and heavy rains to portions of the Azores later
today and tonight.  Please see products issued by the Portuguese
Institute for the Sea and the Atmosphere (IPMA) for more
information.

The northeastward acceleration continues, with Sebastian moving
050/29 kt.  Additional acceleration is expected during the next 24
hours, with the new NHC track forecast a little faster than the
previous iteration and generally a blend of the TVCN and HCCA
consensus aids.  No forecast points are provided starting at 72
hours since by that time Sebastien is expected to have merged with
another weather system southwest of Ireland and the United Kingdom.
This larger complex system could bring gusty winds and heavy rains
to portions of western Europe within the next few days.


FORECAST POSITIONS AND MAX WINDS

INIT  24/0900Z 36.0N  40.0W   55 KT  65 MPH
 12H  24/1800Z 38.5N  34.8W   55 KT  65 MPH
 24H  25/0600Z 42.1N  26.2W   50 KT  60 MPH...POST-TROP/EXTRATROP
 36H  25/1800Z 46.2N  17.5W   45 KT  50 MPH...POST-TROP/EXTRATROP
 48H  26/0600Z 50.0N  11.4W   45 KT  50 MPH...POST-TROP/EXTRATROP
 72H  27/0600Z...MERGED WITH ANOTHER WEATHER SYSTEM

$$
Forecaster Berg

 

[Hurricane Agnes]

5 pm update (not much change other than forward motion and expected to become post-tropical some time tomorrow) -

Quote

654 
WTNT35 KNHC 242058
TCPAT5

BULLETIN
Tropical Storm Sebastien Advisory Number  22
NWS National Hurricane Center Miami FL       AL202019
500 PM AST Sun Nov 24 2019

...SEBASTIEN OR ITS REMNANTS EXPECTED TO BRING GUSTY WINDS AND RAIN
TO PORTIONS OF THE AZORES THROUGH MONDAY MORNING...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...39.2N 32.5W
ABOUT 310 MI...495 KM WNW OF THE AZORES
MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/H
PRESENT MOVEMENT...ENE OR 60 DEGREES AT 39 MPH...63 KM/H
MINIMUM CENTRAL PRESSURE...994 MB...29.36 INCHES


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

Interests in the Azores should monitor the progress of Sebastien.


DISCUSSION AND OUTLOOK
----------------------
At 500 PM AST (2100 UTC), the center of Tropical Storm Sebastien was
located near latitude 39.2 North, longitude 32.5 West. Sebastien is
moving toward the east-northeast near 39 mph (63 km/h).  An even
faster motion toward the northeast or east-northeast is expected
during the next day or so.  On the forecast track, the center of
Sebastien will pass near the western Azores tonight.

Maximum sustained winds are near 65 mph (100 km/h) with higher
gusts.  A slow decrease in the maximum winds is expected during the
next day or so. Sebastien is forecast to become post-tropical
by early Monday, and it could degenerate into a trough of low
pressure at any time during the next couple of days. Regardless of
status, Sebastien or its remnants will likely continue to produce
tropical-storm-force winds for at least a couple more days.

Tropical-storm-force winds extend outward up to 140 miles (220 km)
from the center.

The estimated minimum central pressure is 994 mb (29.36 inches).


HAZARDS AFFECTING LAND
----------------------
WIND AND RAIN:  Sebastien or its remnants are expected to bring
gusty winds and rain to the Azores through Monday morning. Please
see products issued by the Portuguese Institute for the Sea and the
Atmosphere (IPMA) for more information.

SURF:  Swells generated by Sebastien are expected to affect the
Azores during the next couple of days.  These swells are likely to
cause life-threatening surf and rip current conditions.


NEXT ADVISORY
-------------
Next complete advisory at 1100 PM AST.

$$
Forecaster Cangialosi

Quote

000
WTNT45 KNHC 242059
TCDAT5

Tropical Storm Sebastien Discussion Number  22
NWS National Hurricane Center Miami FL       AL202019
500 PM AST Sun Nov 24 2019

Sebastien is gradually losing tropical characteristics.  Satellite
images show a large shield of relatively cold cloud tops on the
north side of the system and in a band that extends from east of the
center south-southwestward.  This cloud pattern resembles an
extratropical cyclone.  However, satellite images and microwave data
also show a small area of deep convection lingering over the center,
which is why the system is still designated a tropical cyclone for
now.  That being said, it is still not clear that the surface
circulation of the storm is well defined. Hopefully, ASCAT data
later this evening can help assess the structure of the circulation.
The initial intensity is held at 55 kt, which is in agreement with
the most recent SATCON estimate from CIMSS at the University of
Wisconsin.

Sebastien is expected to slowly weaken as it remains in very strong
wind shear conditions while moving over progressively colder
waters. FSU phase-analysis diagrams from the global models all show
Sebastien becoming fully extratropical overnight, and the NHC
forecast follows that scenario.  The extratropical low is expected
to merge with another cyclone in 24 to 36 hours.  It is also
possible, as alluded to above, that Sebastien could open into a
trough before then.

Sebastien is racing toward the east-northeast ahead of a cold front,
and the initial motion estimate is 060/34 kt.  This continued
heading at an even faster rate is expected within the fast
mid-latitude flow until the cyclone dissipates.

Regardless of whether it is a tropical cyclone, extratropical
cyclone, or a remnant trough, Sebastien or its remnants will likely
bring gusty winds and heavy rains to portions of the Azores through
Monday morning.  Please see products issued by the Portuguese
Institute for the Sea and the Atmosphere (IPMA) for more
information.


FORECAST POSITIONS AND MAX WINDS

INIT  24/2100Z 39.2N  32.5W   55 KT  65 MPH
 12H  25/0600Z 42.2N  25.7W   55 KT  65 MPH...POST-TROP/EXTRATROP
 24H  25/1800Z 46.3N  17.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 36H  26/0600Z...MERGED WITH ANOTHER EXTRATROPICAL LOW

$$
Forecaster Cangialosi

 

[Hurricane Agnes]

As of the 11 pm update, Sebastien is now post-tropical -

Quote

ZCZC MIATCPAT5 ALL
TTAA00 KNHC DDHHMM

BULLETIN
Post-Tropical Cyclone Sebastien Advisory Number  23
NWS National Hurricane Center Miami FL       AL202019
1100 PM AST Sun Nov 24 2019

...SEBASTIEN NO LONGER A TROPICAL CYCLONE...
...THIS IS THE LAST ADVISORY...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...41.0N 28.9W
ABOUT 230 MI...370 KM NNW OF THE AZORES
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...NE OR 55 DEGREES AT 40 MPH...65 KM/H
MINIMUM CENTRAL PRESSURE...993 MB...29.33 INCHES


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

Interests in the Azores should monitor the progress of the
remnants of Sebastien.


DISCUSSION AND OUTLOOK
----------------------
At 1100 PM AST (0300 UTC), the center of Post-Tropical Cyclone
Sebastien was located near latitude 41.0 North, longitude 28.9 West.
Sebastien is moving toward the northeast near 40 mph (65 km/h) and
this motion is expected to continue for the next day or so.

Maximum sustained winds are near 60 mph (95 km/h) with higher gusts.
Post-tropical cyclone Sebastien should maintain its intensity
before merging with another low during the next day or two.

Gale-force winds extend outward up to 220 miles (350 km)
from the center.

The estimated minimum central pressure is 993 mb (29.33 inches).


HAZARDS AFFECTING LAND
----------------------
WIND AND RAIN:  The cyclone is expected to bring gusty winds and
rain to the Azores through Monday morning. Please see products
issued by the Portuguese Institute for the Sea and the Atmosphere
(IPMA) for more information.

SURF:  Swells generated by Sebastien are expected to affect the
Azores during the next couple of days.  These swells are likely to
cause life-threatening surf and rip current conditions.


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

Additional information on this system can be found in:

High Seas Forecasts issued by Meteo France under WMO header FQNT50
LFPW and on the web at:
www.meteofrance.com/previsions-meteo-marine/bulletin/grandlarge/
metarea2

$$
Forecaster Latto
NNNN

 

Quote

ZCZC MIATCDAT5 ALL
TTAA00 KNHC DDHHMM

Post-Tropical Cyclone Sebastien Discussion Number  23
NWS National Hurricane Center Miami FL       AL202019
1100 PM AST Sun Nov 24 2019

Sebastien has lost its tropical characteristics this evening. The
deep convection has decoupled from the low-level circulation, and
these features are now separated by a distance of 100 n mi and
increasing. Two partial ASCAT passes revealed that the surface low
is becoming stretched out, and there is some evidence of a boundary,
possibly a front, extending northeast from the center. Furthermore,
recent observations from Corbo and Flores islands in the Azores
indicated a slight temperature decrease as the center passed by to
the north of those islands, suggesting that a weak cold front is
associated with the the cyclone. Based on all of these data, there
is high confidence that Sebastien has transitioned to an
extratropical cyclone. The initial advisory intensity is 50 kt which
is based on 47 kt winds sampled by the scatterometer and a
subjective intensity estimate from TAFB.

Post-tropical cyclone Sebastien is moving northeastward at 35 kt,
embedded in the strong flow to the southeast of a mid- to upper-
level trough. This motion, and the cyclone's current intensity, is
expected to persist for the next day or so, before the cyclone
merges with a higher-latitude low.

The cyclone will likely bring gusty winds and heavy rains to
portions of the Azores through Monday morning.  Please see products
issued by the Portuguese Institute for the Sea and the Atmosphere
(IPMA) for more details.

Additional information on this system can be found in:

High Seas Forecasts issued by Meteo France under WMO header FQNT50
LFPW and on the web at
www.meteofrance.com/previsions-meteo-marine/bulletin/grandlarge/
metarea2.

FORECAST POSITIONS AND MAX WINDS

INIT  25/0300Z 41.0N  28.9W   50 KT  60 MPH...POST-TROP/EXTRATROP
 12H  25/1200Z 43.6N  22.7W   50 KT  60 MPH...POST-TROP/EXTRATROP
 24H  26/0000Z 48.1N  14.2W   50 KT  60 MPH...POST-TROP/EXTRATROP
 36H  26/1200Z...MERGED WITH ANOTHER LOW

$$
Forecaster Latto

NNNN