Remnants of Ten Forecast Discussion


000
WTNT45 KNHC 020238
TCDAT5

Remnants Of Ten Discussion Number   6
NWS National Hurricane Center Miami FL       AL102020
200 AM CVT Sun Aug 02 2020

Scatterometer data around 2130 UTC confirmed that the system north 
of the Cabo Verde islands no longer has a well-defined center. The 
scatterometer data showed that the southwest semicircle of the 
system consists of only light and variable winds, and the strongest 
winds associated with the system have decreased to around 20 kt. The 
system lacks deep convection and a combination of cool underlying 
water and a dry surrounding environment will prevent regeneration. 
This is the last NHC advisory on this system.


FORECAST POSITIONS AND MAX WINDS

INIT  02/0300Z 19.5N  25.0W   20 KT  25 MPH...REMNANTS OF TEN
 12H  02/1200Z...DISSIPATED

$$
Forecaster Zelinsky

Post-Tropical Cyclone Edouard Forecast Discussion


000
WTNT45 KNHC 062033
TCDAT5

Post-Tropical Cyclone Edouard Discussion Number  10
NWS National Hurricane Center Miami FL       AL052020
500 PM AST Mon Jul 06 2020

Although Edouard continues to produce some deep convection, recent
satellite imagery and scatterometer data indicate that the center of
the cyclone has merged with a frontal boundary. Therefore, the
system is now classified as extratropical and this is the last
advisory. The scatterometer data showed max winds of 35-40 kt, so
the initial intensity remains 40 kt.  The 35 kt wind radii were 
also increased in the southeast quadrant based on the scatterometer 
data.

The post-tropical cyclone is forecast to continue moving quickly 
northeastward for the next day or so until it is absorbed into a 
larger frontal zone over the north Atlantic late Tuesday or early 
Wednesday. The NHC track and intensity forecast is close to the 
global model consensus, and all of those models are in good 
agreement for the next 24 h.

This is the last NHC advisory on Edouard. Additional information on 
this system can be found in High Seas Forecasts issued by the 
National Weather Service, under AWIPS header NFDHSFAT1, WMO header 
FZNT01 KWBC, and online at ocean.weather.gov/shtml/NFDHSFAT1.php

FORECAST POSITIONS AND MAX WINDS

INIT  06/2100Z 42.7N  46.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
 12H  07/0600Z 45.1N  40.7W   40 KT  45 MPH...POST-TROP/EXTRATROP
 24H  07/1800Z 48.5N  33.2W   40 KT  45 MPH...POST-TROP/EXTRATROP
 36H  08/0600Z...DISSIPATED

$$
Forecaster Zelinsky

Tropical Storm Edouard Forecast Discussion


773 
WTNT45 KNHC 060238
TCDAT5

Tropical Storm Edouard Discussion Number   7
NWS National Hurricane Center Miami FL       AL052020
1100 PM AST Sun Jul 05 2020

Satellite images indicate that the cyclone has become better 
organized during the past several hours, with a large convective 
burst causing a better-defined low-level circulation.  While the 
center is now becoming exposed due to southwesterly shear, the 
maximum winds have almost certainly increased from earlier, so the 
initial wind speed is set to 35 kt. A recent partial ASCAT pass of 
at least 30 kt outside the RMW also supports the upgrade to a 
tropical storm, and the CIMSS satellite consensus (SATCON) is even 
higher than the analyzed intensity.  

Edouard is moving northeastward even faster than before, or 055/30 
kt. Model guidance is in fairly good agreement on a quick 
northeastward or east-northeastward motion for the next couple of 
days before the system degenerates into a trough.  Extratropical 
transition is anticipated by 24 hours due to forcing from a 
middle-latitude trough and a frontal boundary.  Some minor 
strengthening of Edouard due to the transition process is possible 
over the next day or so before the global models show a gradual 
weakening.  The track forecast has been adjusted a bit faster to 
account for the latest guidance and initial forward speed, and the 
intensity forecast has also been nudged upward to account for the 
current wind speed.

Edouard is the earliest known 5th named storm on record for the 
Atlantic basin in the satellite era (1966-present), breaking the 
record formerly held by Emily on July 12, 2005. 


FORECAST POSITIONS AND MAX WINDS

INIT  06/0300Z 37.2N  56.9W   35 KT  40 MPH
 12H  06/1200Z 39.6N  51.7W   40 KT  45 MPH
 24H  07/0000Z 42.9N  44.6W   40 KT  45 MPH...POST-TROP/EXTRATROP
 36H  07/1200Z 46.5N  37.3W   35 KT  40 MPH...POST-TROP/EXTRATROP
 48H  08/0000Z 50.0N  29.0W   30 KT  35 MPH...POST-TROP/EXTRATROP
 60H  08/1200Z...DISSIPATED

$$
Forecaster Blake


Tropical Depression Five Forecast Discussion


000
WTNT45 KNHC 041451
TCDAT5

Tropical Depression Five Discussion Number   1
NWS National Hurricane Center Miami FL       AL052020
1100 AM AST Sat Jul 04 2020

Late yesterday, a small low pressure system developed near the end 
of a boundary over the western Atlantic. The low persisted overnight 
while producing convection that has shown increasing signs of 
organization. Although the low's center has recently become 
obscured, earlier one-minute visible imagery confirmed that it is 
well-defined. The system therefore meets the necessary criteria to 
be designated as a tropical cyclone. A TAFB Dvorak classification of 
2.0 is the basis for the 30 kt initial intensity.

The depression is moving quickly toward the east-northeast, caught 
in the flow between a mid-level ridge to its south and a a trough 
to its north. This steering pattern is expected to be fairly stable 
for the next day or so, and the guidance is in good agreement that 
the cyclone will continue on its current general heading with an 
increase in forward speed during the next couple of days. The NHC 
track forecast closely follows the TVCN and HCCA consensus aids.

The depression has a sheared appearance, with no convection 
northwest of its low-level center. A combination of strong 
upper-level westerly winds and dry mid-level air to the northwest 
are likely the cause of this, and it is unlikely that the cyclone 
will get much better organized during the next day or two. That 
said, some minimal strengthening is possible, even if only due to 
the expected increase of the cyclone's forward speed. The NHC 
intensity forecast is based on a consensus of the HWRF, HMON, and 
GFS models. It is worth noting that the statistical guidance 
indicates more strengthening is possible, but this is not currently 
supported by any dynamical models. There is less agreement on the 
system's future beyond the weekend. It could open into a trough and 
dissipate or persist long enough to undergo extratropical 
transition. Since this is the first advisory, the official forecast 
is somewhat conservative and maintains the system as a closed low 
for 60 h, but it could certainly dissipate sooner than that.


FORECAST POSITIONS AND MAX WINDS

INIT  04/1500Z 31.1N  68.7W   30 KT  35 MPH
 12H  05/0000Z 32.1N  66.5W   35 KT  40 MPH
 24H  05/1200Z 34.0N  63.5W   35 KT  40 MPH
 36H  06/0000Z 36.4N  59.4W   35 KT  40 MPH
 48H  06/1200Z 39.2N  52.7W   35 KT  40 MPH
 60H  07/0000Z 41.7N  46.8W   40 KT  45 MPH...POST-TROP/EXTRATROP
 72H  07/1200Z...DISSIPATED

$$
Forecaster Zelinsky

Post-Tropical Cyclone Sebastien Forecast Discussion


578 
WTNT45 KNHC 250232
TCDAT5

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


Tropical Storm Sebastien Forecast Discussion


000
WTNT45 KNHC 241441
TCDAT5

Tropical Storm Sebastien Discussion Number  21
NWS National Hurricane Center Miami FL       AL202019
1100 AM AST Sun Nov 24 2019

It is not clear if Sebastien is a closed cyclone at the surface. The
fast forward motion of the cyclone (28 kt) may have caused it to
open into a trough of low pressure. The ship MSC Beijing (DFDE2)
recently reported northwest winds about 70 n mi north-northeast of
the cyclone's estimated center, and it has been difficult to
identify easterly winds in visible imagery this morning. That said,
ASCAT data was inconclusive regarding the state of Sebastien's
circulation and the system is still producing some deep convection
near its center. AMSU data at 1135 UTC also indicated that Sebastien
still has a weak warm core. For those reasons, it appears prudent to
maintain advisories at this time.

As mentioned above, Sebastien is moving very quickly northeastward
and it should accelerate in that direction during the next 24 h.
This is shown by all of the dynamical models which are finally in
decent agreement. Based on simulated satellite imagery, it appears
that the cyclone will continue to produce central deep convection
for the next 12 h or so, and extratropical transition is forecast to
finish within 24 h. Although an extratropical point is shown at 36 h
for continuity purposes, in reality Sebastien will more likely open
into a trough of low pressure, given the forecast forward motion of
nearly 40 kt relative to its 50 kt forecast intensity at this time
tomorrow. This could happen at any time.

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 later
today and tonight. Please see products issued by the Portuguese
Institute for the Sea and the Atmosphere (IPMA) for more
information.


FORECAST POSITIONS AND MAX WINDS

INIT  24/1500Z 37.4N  37.0W   55 KT  65 MPH
 12H  25/0000Z 39.8N  31.0W   55 KT  65 MPH
 24H  25/1200Z 43.8N  22.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 36H  26/0000Z 47.7N  14.8W   45 KT  50 MPH...POST-TROP/EXTRATROP
 48H  26/1200Z...DISSIPATED

$$
Forecaster Zelinsky

Tropical Storm Sebastien Forecast Discussion


606 
WTNT45 KNHC 230833
TCDAT5

Tropical Storm Sebastien Discussion Number  16
NWS National Hurricane Center Miami FL       AL202019
500 AM AST Sat Nov 23 2019

The cloud pattern of Sebastien has changed significantly overnight.
Deep convection has decreased substantially during the past several
hours and the remaining thunderstorms are organized around a
mid-level eye feature seen in satellite images.  Model vertical
cross sections indicate that Sebastien is extremely titled with the
low-level center, although I can't see it, likely well displaced to
the southwest of the mid-level eye.  The initial intensity is held
at 55 kt based on the ASCAT data that came in a little after 00 Z,
but it looks like Sebastien is on a weakening trend.

Strong southwesterly vertically wind shear of about 40 kt is
responsible for the titled structure of the cyclone.  Since the
shear is not expected to let up and because Sebastien is headed for
steadily cooler waters, it seems reasonable to assume that weakening
is likely.  Although the models agree that Sebastien should slowly
lose its strength, it remains unclear if Sebastien will transition
to a post-tropical cyclone before it opens up into a trough during
the next few days.  The NHC forecast continues to show dissipation
by day 3, but it is certainty possible that it dissipates before
then.

The tropical storm is moving east-northeastward at 15 kt ahead of a
cold front and trough.  This motion with an increase in forward
speed is expected during the next few days as Sebastien becomes more
embedded in the faster mid-latitude flow.  The models are in
relatively good agreement, and only small changes were made to the
previous NHC forecast.

The initial wind radii were modified based on the aforementioned
ASCAT passes, and the 12-ft sea radii were adjusted based on ship
and altimeter data.

FORECAST POSITIONS AND MAX WINDS

INIT  23/0900Z 27.8N  50.6W   55 KT  65 MPH
 12H  23/1800Z 29.4N  48.2W   50 KT  60 MPH
 24H  24/0600Z 31.6N  44.2W   45 KT  50 MPH
 36H  24/1800Z 34.0N  38.8W   40 KT  45 MPH
 48H  25/0600Z 37.0N  31.6W   35 KT  40 MPH
 72H  26/0600Z...DISSIPATED

$$
Forecaster Cangialosi


Tropical Storm Sebastien Forecast Discussion


000
WTNT45 KNHC 212032
TCDAT5

Tropical Storm Sebastien Discussion Number  10
NWS National Hurricane Center Miami FL       AL202019
500 PM AST Thu Nov 21 2019

Convection associated with Sebastien has become better organized
during the past several hours, as a band has formed near and over
the center in the eastern semicircle.  Overall, the cloud pattern
remains elongated from north-to-south as the storm is interacting
with a cold front not far to its northwest.  Scatterometer data
received just after the last advisory indicated 45-50 kt winds, and
based on this and current satellite intensity estimates the initial
intensity remains 50 kt.

The cyclone has turned northeastward with the initial motion now
050/8.  Southwesterly mid-latitude flow should steer Sebastien or
its remnants quickly northeastward, and the guidance is in good
agreement on the direction of movement during the next several
days.  However, there is a significant spread in the forward speed,
with the new ECMWF run being much slower than the other guidance.
The new track forecast will be only slightly slower than the
previous forecast, but adjustments to the forecast forward speed
may be necessary later.

Sebastien is in an apparently unfavorable environment for
development due to strong shear, decreasing sea surface temperatures
along the forecast track, and an expected extratropical transition
as it merges with the front.  The intensity guidance is rather
divergent during the first 24 h, with the SHIPS and LGEM models
showing weakening while the dynamical guidance continues to forecast
strengthening despite the environment.  After that time, all
guidance indicates that Sebastien should weaken.  The intensity
forecast continues the trend of the previous forecast in showing
some strengthening during the first 24 h in agreement with the
dynamical models, followed by weakening and extratropical transition
by 48 h. Given how close the cold front is to the storm at this
time, it is possible that extratropical transition could occur
earlier than currently forecast.


FORECAST POSITIONS AND MAX WINDS

INIT  21/2100Z 23.8N  59.7W   50 KT  60 MPH
 12H  22/0600Z 25.5N  57.1W   60 KT  70 MPH
 24H  22/1800Z 27.9N  53.2W   65 KT  75 MPH
 36H  23/0600Z 30.6N  48.4W   55 KT  65 MPH
 48H  23/1800Z 33.5N  43.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
 72H  24/1800Z 39.0N  31.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
 96H  25/1800Z...DISSIPATED

$$
Forecaster Beven

Tropical Storm Sebastien Forecast Discussion


000
WTNT45 KNHC 201447
TCDAT5

Tropical Storm Sebastien Discussion Number   5
NWS National Hurricane Center Miami FL       AL202019
1100 AM AST Wed Nov 20 2019

Sebastien continues to struggle with dry air and northwesterly
shear, with satellite imagery showing an exposed low-level
center to the west of the deep convection. The current structure of
the storm should prevent significant intensification during the next
12 hours. After that time, Sebastien will begin to interact with a
mid- to upper-level trough that will produce upper-level divergence
over the cyclone. This will provide a window for Sebastien to
intensify before making the transition to an extratropical cyclone
in about 48 hours. All available guidance intensifies the storm, and
the dynamical models continue to strengthen it more than the
statistical models. In fact, the mesoscale models unanimously make
Sebastian a hurricane within 36 hours. However, these models are
likely intensifying the cyclone too quickly over the next 12 hours,
and therefore may have a slight high bias. The official forecast
takes this into account and keeps the storm just below hurricane
strength before extratropical transition by 48 hours, which is a
blend of the ECMWF and GFS solutions.

Sebastien appears to be approaching its westernmost point and a turn
to the north should begin later today, followed by acceleration to
the northeast starting tonight due to the influence of the
approaching trough. The track guidance is in agreement on this
overall scenario. The NHC forecast track is just slightly slower
than the previous one in the first 24 hours, and is close to the
model consensus.


FORECAST POSITIONS AND MAX WINDS

INIT  20/1500Z 21.1N  61.7W   45 KT  50 MPH
 12H  21/0000Z 22.0N  61.7W   45 KT  50 MPH
 24H  21/1200Z 23.7N  60.2W   55 KT  65 MPH
 36H  22/0000Z 26.3N  57.2W   60 KT  70 MPH
 48H  22/1200Z 29.8N  52.5W   60 KT  70 MPH...POST-TROP/EXTRATROP
 72H  23/1200Z...DISSIPATED

$$
Forecaster Latto/Mello

Remnants of Fifteen Forecast Discussion


000
WTNT45 KNHC 160833
TCDAT5

Remnants Of Fifteen Discussion Number   7
NWS National Hurricane Center Miami FL       AL152019
500 AM AST Wed Oct 16 2019

Satellite images indicate that the surface circulation of the
system has become rather elongated north-to-south, with only a few
weak swirls in the circulation envelope, and has degenerated into a
trough of low pressure.  Thus it is no longer a tropical cyclone,
and this is the last advisory.  The winds are lowered to 25 kt,
matching the TAFB classification.

The remnants of the cyclone are expected to move northwestward
during the next few days.  There is a slight chance of
regeneration, as suggested by the ECMWF model and some of its
ensemble members due to a trough interaction, but that's considered
unlikely at this point.


FORECAST POSITIONS AND MAX WINDS

INIT  16/0900Z 17.3N  24.1W   25 KT  30 MPH
 12H  16/1800Z...DISSIPATED

$$
Forecaster Blake

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