Tropical Depression Omar Forecast Discussion


000
WTNT45 KNHC 040232
TCDAT5

Tropical Depression Omar Discussion Number  14
NWS National Hurricane Center Miami FL       AL152020
1100 PM AST Thu Sep 03 2020

The larger mass of deep convection from earlier today that was south 
of the exposed low-level center of Omar has since dissipated. The 
only convection that remains is a few small patches in the eastern 
semicircle. The initial intensity is being lowered to 25 kt, and is 
based off a recent ASCAT overpass showing peak 26 kt wind vectors. 
If the current state of the tropical depression persists through 
much of tonight, then by definition the system would no longer 
qualify as a tropical cyclone. The only chance for Omar to hang on 
despite very strong northerly wind shear is the fact that it is 
still over SSTs of about 27 C. After 24 h, dry air is expected to 
envelop the system. Therefore, over this weekend whatever remains of 
Omar is expected to dissipate ahead of an approaching mid-latitude 
frontal system. The official NHC forecast shows Omar degenerating 
into a remnant low by Friday morning and dissipating by Sunday 
morning, and this scenario is in agreement with the global models.

The depression continues to move east-southeast at 9 kt in steering
flow around a subtropical ridge to its south, and another, larger
low pressure system to its northeast. The other low is forecast to
continue to lift northeastward, which should result in an end to the
southerly component of Omar's motion tonight or early Friday. By
Friday night, a turn to the northeast is expected to occur as Omar
gets caught in southwesterly flow ahead of the approaching frontal
system. The latest NHC track forecast is little changed from the
previous one, and lies near the various consensus aids.


FORECAST POSITIONS AND MAX WINDS

INIT  04/0300Z 35.2N  59.1W   25 KT  30 MPH
 12H  04/1200Z 35.2N  58.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 24H  05/0000Z 35.6N  57.2W   25 KT  30 MPH...POST-TROP/REMNT LOW
 36H  05/1200Z 36.8N  56.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  06/0000Z 38.3N  55.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
 60H  06/1200Z...DISSIPATED

$$
Forecaster Latto

Tropical Storm Omar Forecast Discussion


000
WTNT45 KNHC 021448
TCDAT5

Tropical Storm Omar Discussion Number   8
NWS National Hurricane Center Miami FL       AL152020
1100 AM AST Wed Sep 02 2020

Although is seems as though we've been predicting it ad nauseam,
the persistent, blistering shear has finally begun to dramatically
affect the cyclone.  What remains of the deep convective cloud mass
is separated more than 100 miles east-southeast of the exposed
surface circulation.  The initial intensity is held at 35 kt based 
on the Dvorak satellite intensity estimates from TAFB and SAB using 
the shear scene-type.  Omar's winds should begin to decrease later 
tonight as the exposed surface center further decouples from the 
convective mass.  A few of the large-scale models show Omar 
dissipating as soon as Friday, but for this NHC intensity forecast, 
I'll indicate weakening to a depression Thursday, followed by 
degeneration to a remnant low in 36 hours, similar to the 
multi-model consensus intensity aids and the LGEM.  

Omar's initial motion is estimated to be eastward, or 080/11 kt, and 
is being steered by the deep-layer mid-latitude westerlies produced 
by a subtropical ridge anchored over the central Atlantic.  Omar 
should continue on this general course through Friday.  On 
Saturday, the remnant low is expected to slow a bit, and turn 
toward the east-northeast in response to an approaching frontal 
boundary moving away from the Canadian Maritimes.  No significant 
changes were made to the previous track forecast, and the new NHC 
forecast is based on a blend of the HCCA and GFEX consensus models.



FORECAST POSITIONS AND MAX WINDS

INIT  02/1500Z 36.2N  67.4W   35 KT  40 MPH
 12H  03/0000Z 36.5N  65.4W   35 KT  40 MPH
 24H  03/1200Z 36.5N  62.4W   30 KT  35 MPH
 36H  04/0000Z 36.3N  59.9W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  04/1200Z 36.2N  58.1W   25 KT  30 MPH...POST-TROP/REMNT LOW
 60H  05/0000Z 36.4N  56.9W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  05/1200Z 37.0N  55.8W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  06/1200Z...DISSIPATED

$$
Forecaster Roberts

Tropical Depression Fifteen Forecast Discussion


000
WTNT45 KNHC 010239
TCDAT5

Tropical Depression Fifteen Discussion Number   2
NWS National Hurricane Center Miami FL       AL152020
1100 PM EDT Mon Aug 31 2020

Tropical Depression Fifteen is a sheared tropical cyclone, with the 
edge of the deep convection displaced nearly 30 n mi to the east of 
the exposed low-level center. An Air Force Reserve Hurricane Hunter 
mission earlier this evening provided SFMR instrument measurements 
of nearly 30 kt in the southeast quadrant. And, a recent ASCAT 
overpass showed several wind vectors in that same general area 
between 25-30 kt. Therefore, the initial intensity is being held at 
30 kt. 

The depression is moving northeast at 12 kt around the northwestern 
periphery of the subtropical ridge. A turn to the east-northeast is 
expected to occur on Tuesday as the cyclone moves along the 
northern periphery of the ridge. Late in the forecast period, what 
is left of the cyclone is forecast to get caught in the flow 
between building high pressure to its northeast, and an approaching 
trough to its northwest, which should induce a more northerly 
component of motion. The latest NHC forecast is little changed from 
the previous one, and is near the tightly clustered track guidance. 

The cyclone has moved into an environment with moderate westerly 
shear of about 20 kt, as indicated by the latest UW-CIMSS deep-layer 
shear analysis product. The SHIPS guidance by both the GFS and ECMWF 
indicate that the shear magnitude will more than double between 18 h 
and 36 h from now.  So it is anticipated that the only window of 
time for the depression to strengthen will be tonight through 
tomorrow, while the system is over warm waters and in a moist 
atmospheric environment. After 48 h, when the vertical wind shear is 
forecast to be between 40 and 50 kt, the cyclone is forecast to 
weaken, and by 96 h the NHC forecast now shows the system 
degenerating into a remnant low. Exactly what transpires with the 
cyclone later in the forecast period remains uncertain, as some of 
the global models suggest that the cyclone will open into a trough 
in a few days, while others indicate that the system could be 
absorbed by a larger mid-latitude trough around day 5. Regardless of 
what occurs by those time frames, the models all suggest that the 
system should not gain much more strength than it currently has. The 
official NHC intensity forecast is in good agreement with the 
various intensity consensus aids.


FORECAST POSITIONS AND MAX WINDS

INIT  01/0300Z 33.2N  75.7W   30 KT  35 MPH
 12H  01/1200Z 34.2N  74.0W   35 KT  40 MPH
 24H  02/0000Z 35.1N  71.2W   35 KT  40 MPH
 36H  02/1200Z 36.0N  68.6W   35 KT  40 MPH
 48H  03/0000Z 36.9N  65.9W   35 KT  40 MPH
 60H  03/1200Z 37.7N  63.3W   30 KT  35 MPH
 72H  04/0000Z 38.1N  60.5W   30 KT  35 MPH
 96H  05/0000Z 38.7N  55.8W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  06/0000Z 41.6N  50.4W   30 KT  35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Latto

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


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