ATL: GASTON - Post-Tropical - Discussion

[cycloneye]

...GASTON FORECAST TO REGAIN HURRICANE INTENSITY...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...26.2N 49.7W
ABOUT 1000 MI...1610 KM ESE OF BERMUDA
ABOUT 1020 MI...1640 KM NE OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/H
PRESENT MOVEMENT...NW OR 320 DEGREES AT 17 MPH...28 KM/H
MINIMUM CENTRAL PRESSURE...997 MB...29.44 INCHES

[CrazyC83]

TXNT24 KNES 270002
TCSNTL

A. 07L (GASTON)

B. 26/2345Z

C. 26.7N

D. 50.4W

E. THREE/GOES-E

F. T3.5/3.5/S0.0/24HRS

G. IR/EIR/SWIR/SSMIS

H. REMARKS...CENTER LOCATED AT LEAST 1/3 DEGREE INTO DG FOR A DT OF
3.5 USING SHEAR PATTERN. MET AND PT AGREE. FT IS BASED ON DT.

I. ADDL POSITIONS

26/2129Z 26.4N 49.8W SSMIS


...VELASCO

It was previously T2.5/3.0.

[cycloneye]

TROPICAL STORM GASTON DISCUSSION NUMBER 18
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072016
1100 PM AST FRI AUG 26 2016

The structure of Gaston appears to be slowly improving, with less
evidence of vertical shear than earlier today. Deep convection has
been forming fairly close to the center in a more symmetric fashion,
but still hasn't been able to persist for very long. Subjective
estimates are a little higher than earlier, but still support an
initial wind speed of 55 kt for this advisory.

Gaston should move into a low-shear, warm-water environment during
the next 2 or 3 days, which would usually support a great deal of
strengthening. However, a key hindering factor remains the nearby
low-level moisture, which is forecast to substantially decrease
during the next few days. This should temper the expected
intensification and reduce the chances for rapid strengthening.
Gaston is likely to encounter increasing upper-level flow beyond 3
days, which probably will start a weakening trend in combination
with gradually cooling SSTs. Model guidance is generally in good
agreement on this scenario, with less spread in the intensity
models than is typically seen. The new prediction is a blend of
the previous forecast and the intensity consensus.

Microwave data suggest that Gaston continues to move northwestward,
now at about 13 kt, a bit slower than before. The cyclone is
moving between a strong upper low to the southwest and a subtropical
ridge to its northeast. The ridge is forecast to gradually weaken,
resulting in Gaston decelerating over the next couple of days.
Steering currents get quite light in about 3 days, and the cyclone
is expected to turn northeastward or east-northeastward it moves
around the northwest side of a distant ridge over the eastern
Atlantic. Computer models are coming into better agreement on a
sharper, slower recurvature, first suggested by the ECMWF yesterday.
The latest NHC forecast is close to the previous one for the first
few days, then is trended eastward to follow the model trend.


FORECAST POSITIONS AND MAX WINDS

INIT 27/0300Z 27.0N 50.8W 55 KT 65 MPH
12H 27/1200Z 28.0N 52.5W 60 KT 70 MPH
24H 28/0000Z 29.2N 54.1W 70 KT 80 MPH
36H 28/1200Z 30.2N 55.2W 80 KT 90 MPH
48H 29/0000Z 30.8N 55.7W 90 KT 105 MPH
72H 30/0000Z 31.8N 55.4W 95 KT 110 MPH
96H 31/0000Z 33.0N 52.0W 90 KT 105 MPH
120H 01/0000Z 35.0N 47.5W 80 KT 90 MPH

$$
Forecaster Blake

[Socalhurcnegirl227]

saw this and couldnt breathe from laughter good comedy if anyone hasnt seen this

[cycloneye]

TROPICAL STORM GASTON DISCUSSION NUMBER 19
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072016
500 AM AST SAT AUG 27 2016

Recent microwave data indicate that Gaston's center is now well
embedded near the middle of the central dense overcast. The
microwave images also show that a partial mid-level ring has formed,
but it remains open to the north-northeast. Even though Gaston's
structure appears to be improving, the maximum winds remain 55 kt
based on Dvorak Current Intensity numbers from TAFB and SAB.

Two outflow jets are emanating away to the east and southwest of
Gaston, but the outflow remains restricted to the south and
northwest. Still, the shear has decreased substantially from what
it was a day or two ago, and it should remain generally low for the
next 48 hours. In addition, sea surface temperatures ahead of
Gaston are expected to be at least 28C for several more days.
Therefore, strengthening is anticipated through day 3, followed by
gradual weakening on days 4 and 5 due to increasing westerly shear.
Although the intensity models all agree on this general scenario,
there is a little more spread in the peak intensities than has been
noted in previous advisories. On the high end, the Florida State
Superensemble still shows Gaston approaching major hurricane
intensity, while the LGEM model is at the other extreme being about
20 kt lower. The updated NHC intensity forecast is near the middle
of the guidance and ends up just a little lower than the previous
forecast.

Gaston is moving northwestward, or 310 degrees at 13 kt, between a
mid-tropospheric high to its northeast and a mid-/upper-level low
to its southwest. The cyclone is expected to maintain a
northwestward heading but steadily decelerate during the next 48
hours. After that time, Gaston should recurve sharply
east-northeastward and accelerate through the end of the forecast
period as it gets picked up by the mid-latitude westerlies. The
track guidance has trended westward through 48 hours, delaying
Gaston's recurvature just a bit, and it is then a little faster by
days 4 and 5. The NHC track forecast has been adjusted accordingly
and is close to the TVCN multi-model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT 27/0900Z 27.9N 52.0W 55 KT 65 MPH
12H 27/1800Z 28.8N 53.6W 60 KT 70 MPH
24H 28/0600Z 29.9N 55.0W 70 KT 80 MPH
36H 28/1800Z 30.6N 56.0W 80 KT 90 MPH
48H 29/0600Z 31.2N 56.8W 85 KT 100 MPH
72H 30/0600Z 32.5N 55.6W 90 KT 105 MPH
96H 31/0600Z 34.5N 50.5W 85 KT 100 MPH
120H 01/0600Z 37.0N 43.5W 75 KT 85 MPH

$$
Forecaster Berg

[tolakram]

live visible

http://weather.msfc.nasa.gov/cgi-bin/get-goes?satellite=GOES-E%20HURRICANE&lat=29&lon=-53&info=vis&zoom=1&width=1024&height=768&type=Animation&quality=92&palette=ir1.pal&numframes=5&mapcolor=gray

[cycloneye]

TROPICAL STORM GASTON DISCUSSION NUMBER 20
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072016
1100 AM AST SAT AUG 27 2016

A 0954Z WindSAT microwave image indicated that Gaston had developed
a 15-nmi-diameter low-level eye that was embedded in the center of
the nearly circular central dense overcast. Subjective satellite
intensity estimates are T4.0/65 kt and T3.5/55 kt from TAFB and
SAB, respectively, and the latest UW-CIMSS ADT value is T3.7/59 kt.
An average of these estimates supports increasing the initial
intensity to 60 kt.

As anticipated, Gaston has slowed down and the motion estimate is
now 310/09 kt. The cyclone is forecast to maintain a northwestward
motion and continue to decelerate during the next 48 hours as Gaston
moves into a break in the subtropical ridge located to its north. A
mid-level shortwave trough is forecast to dig southeastward from
Canada and the northeastern United States by 72 hours, and force
Gaston to make a sharp turn toward the north and northeast when the
cyclone is located several hundred miles east of Bermuda. On days 4
and 5, Gaston is expected to get caught up in the deep-layer mid-
latitude westerlies and accelerate east-northeastward over the North
Atlantic. The new official forecast track is a little slower than
the previous advisory track and has been shifted a little to the
east, but not nearly as far east as the consensus model TVCN out of
respect for the ECWMF model, which is close to the previous
forecast track.

Gaston has maintained two pronounced upper-level outflow jets to its
east and southwest. These jets are flowing into large upper-level
lows that are acting as significant mass sinks, a pattern that
favors intensification. Although the mid-level environment is
expected to be characterized by low humidity values of 40-45 percent
during the next 72 hours, the cyclone will be moving over SSTs of
29C and remain in a low vertical wind shear regime. Those latter
conditions, along with the small eye feature and the outflow jet
pattern should allow Gaston to overcome the dry conditions and
result in strengthening at a typical rate of about 20 kt per day. By
days 4 and 5, the vertical shear is forecast to increase sharply and
become westerly at more than 30 kt, which should induce a weakening
trend. The NHC intensity forecast is similar to the previous
advisory, and lies close to the consensus model IVCN through 36
hours, and a little above IVCN and close to the SHIPS/LGEM models
after that.

FORECAST POSITIONS AND MAX WINDS

INIT 27/1500Z 28.4N 53.2W 60 KT 70 MPH
12H 28/0000Z 29.3N 54.3W 65 KT 75 MPH
24H 28/1200Z 30.1N 55.3W 75 KT 85 MPH
36H 29/0000Z 30.7N 56.0W 85 KT 100 MPH
48H 29/1200Z 31.3N 56.3W 90 KT 105 MPH
72H 30/1200Z 32.6N 54.4W 90 KT 105 MPH
96H 31/1200Z 34.2N 49.6W 80 KT 90 MPH
120H 01/1200Z 36.9N 43.7W 70 KT 80 MPH

$$
Forecaster Stewart

[cycloneye]

 https://twitter.com/WxForecastSolns/status/769567346079961089

[cycloneye]

TROPICAL STORM GASTON DISCUSSION NUMBER 21
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072016
500 PM AST SAT AUG 27 2016

The inner-core convection of Gaston has continued to increase with
the CDO having expanded and become more symmetrical. Subjective
satellite intensity estimates remain T4.0/65 kt and T3.5/55 kt from
TAFB and SAB, respectively, and the latest UW-CIMSS ADT value is
T3.9/63 kt. An average of these estimates supports maintaining the
initial intensity at 60 kt, which could be conservative.

Gaston's initial motion estimate is 320/08 kt. There is no
significant change to the previous forecast track reasoning. Gaston
is expected to continue moving northwestward and gradually
decelerate during the next two days as the cyclone moves into a
break in the Bermuda-Azores ridge. A shortwave trough and associated
frontal system is forecast to approach Gaston by 72 hours and slowly
lift out the tropical cyclone to the north and northeast. On days 4
and 5, Gaston is expected to get caught up in the mid-latitude
westerly flow ahead of the aforementioned frontal system and
accelerate east-northeastward. The new NHC track model guidance is
in much better agreement now that the ECMWF model has made a
significant eastward shift in its track forecast and is much closer
to the previous advisory track. The new official forecast track was
only shifted eastward slightly to come more in line with the
consensus models TVCN and GFEX. However, the track shift also
resulted in a significant decrease in the forward speed on days 3,
4, and 5.

The global and regional models continue to indicate that Gaston
will remain in a very favorable upper-level outflow pattern for at
least the next 72 hours. In fact, the Navy-COAMPS, GFS, and ECMWF
models forecast Gaston to become a major hurricane by 72-120 h, with
the ECMWF forecasting a central pressure of 945 mb on day 5. In
contrast, the HWRF and the statistical-dynamical models SHIPS/LGEM
only bring Gaston up to 85-90 kt. Due to the possibility of
occasional dry air intrusions, with mid-level humidity values in the
40-percent range, weakening the inner-core convection, the official
intensity forecast remains unchanged and on the conservative side
through 72 hours, which is slightly above the consensus model IVCN.
On days 4 and 5, strong westerly shear of about 30 kt should induce
weakening, which also argues against this system becoming a major
hurricane at that time like the ECMWF model is predicting, and the
forecast is a little lower than the consensus on those days.

FORECAST POSITIONS AND MAX WINDS

INIT 27/2100Z 29.2N 54.0W 60 KT 70 MPH
12H 28/0600Z 30.0N 54.6W 70 KT 80 MPH
24H 28/1800Z 30.7N 55.1W 80 KT 90 MPH
36H 29/0600Z 31.0N 55.3W 85 KT 100 MPH
48H 29/1800Z 31.4N 54.9W 90 KT 105 MPH
72H 30/1800Z 32.5N 53.0W 85 KT 100 MPH
96H 31/1800Z 34.0N 50.0W 75 KT 85 MPH
120H 01/1800Z 37.0N 44.0W 65 KT 75 MPH

$$
Forecaster Stewart

[Hammy]

Eye forming in latest image.

[Kazmit]

Eye forming in latest image.

I noticed this. Should definitely be a hurricane by 11pm EDT.

[cycloneye]

00z Best Track.Hurricane at 11 PM EDT.

AL, 07, 2016082800, , BEST, 0, 292N, 541W, 75, 980, HU

CrazyC83,ATCF fixed the 18z data as Hurricane at 65kts.

AL, 07, 2016082718, , BEST, 0, 287N, 536W, 65, 989, HU

[Hammy]

Outflow is starting to expand quite nicely to the northwest in the last hour or so.

[CrazyC83]

TXNT24 KNES 280009
TCSNTL

A. 07L (GASTON)

B. 27/2345Z

C. 29.2N

D. 54.0W

E. ONE/GOES-E

F. T4.5/4.5/D1.0/24HRS

G. IR/EIR/SWIR/WINDSAT

H. REMARKS...A MG EYE SURROUNDED BY B RESULTS IN A 0.0 EYE
ADJUSTMENT. THE EYE IS EMBEDDED IN MG YIELDING AN E# OF 4.5 FOR A DT OF
4.5. THE MET AND PT AGREE. FT IS BASED ON DT.

I. ADDL POSITIONS

27/2111Z 29.0N 53.9W WINDSAT


...MICHAEL

Basis for the 75 kt intensity. I'd also raise the forecast peak to 100 or 105 kt.

[cycloneye]

...GASTON AGAIN A HURRICANE, NOW WITH 85-MPH WINDS...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...29.6N 54.2W
ABOUT 655 MI...1055 KM ESE OF BERMUDA
MAXIMUM SUSTAINED WINDS...85 MPH...140 KM/H
PRESENT MOVEMENT...NW OR 320 DEGREES AT 8 MPH...13 KM/H
MINIMUM CENTRAL PRESSURE...980 MB...28.94 INCHES


HURRICANE GASTON DISCUSSION NUMBER 22
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072016
1100 PM AST SAT AUG 27 2016

Gaston has become a hurricane again with a well-defined eye on
microwave images that has been occasionally showing up on
conventional satellite pictures. Dvorak estimates are T4.5/77 kt
from both TAFB and SAB, so the initial wind speed is increased to 75
kt. The environment near Gaston, other than some dry mid-level air,
looks conducive for strengthening for the next day or so. While
the environment doesn't change much in the next couple of days
overall, Gaston is expected to move very slowly, which could upwell
some cooler water. Thus the wind speed forecast will be leveled
off after 24 hours. A more consistent weakening trend is expected
beyond 72 hours when the cyclone moves over colder waters and
experiences stronger shear. The latest NHC prediction is higher
than the previous one, mostly owing to the initial conditions, and
is close to a blend of the FSU Superensemble and the intensity
consensus.

Satellite fixes show that Gaston is moving slower to the northwest,
at about 7 kt. The storm should continue to decelerate over the
next day or so as it reaches a break in the subtropical ridge, and
have a slow motion to the north or northeast from 24 to 48 hours.
The next shortwave trough in the mid-latitude is forecast to reach
Gaston in about 3 days, which will likely cause the hurricane to
recurve to the east-northeast, albeit at a slower rate of speed than
you normally see over the North Atlantic. Guidance has not changed
much since the last cycle, and the official forecast is basically an
update of the previous one, a bit slower than the model consensus.


FORECAST POSITIONS AND MAX WINDS

INIT 28/0300Z 29.6N 54.2W 75 KT 85 MPH
12H 28/1200Z 30.1N 54.7W 85 KT 100 MPH
24H 29/0000Z 30.7N 55.1W 95 KT 110 MPH
36H 29/1200Z 31.0N 55.2W 95 KT 110 MPH
48H 30/0000Z 31.4N 54.8W 90 KT 105 MPH
72H 31/0000Z 32.6N 52.2W 90 KT 105 MPH
96H 01/0000Z 34.6N 48.1W 85 KT 100 MPH
120H 02/0000Z 37.5N 42.0W 70 KT 80 MPH

$$
Forecaster Blake

[cycloneye]

...GASTON AGAIN A HURRICANE, NOW WITH 85-MPH WINDS...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...29.6N 54.2W
ABOUT 655 MI...1055 KM ESE OF BERMUDA
MAXIMUM SUSTAINED WINDS...85 MPH...140 KM/H
PRESENT MOVEMENT...NW OR 320 DEGREES AT 8 MPH...13 KM/H
MINIMUM CENTRAL PRESSURE...980 MB...28.94 INCHES

[Kazmit]

Woah, Gaston's already Alex's peak strength. A major is looking increasingly likely.

[cycloneye]

HURRICANE GASTON DISCUSSION NUMBER 23
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072016
500 AM AST SUN AUG 28 2016

For much of the night, there was little overall change in the
organization of Gaston. A ragged eye had occasionally been seen
in infrared satellite imagery, and an 0529 UTC AMSR microwave
overpass detected an eye that was open over the southwestern
quadrant. However, within the past hour or so, the eye has become a
little more apparent, with some cooling to the surrounding cloud
tops. As a result, the initial intensity has been increased to 80
kt, which is slightly above the latest subjective Dvorak estimates
because of the recent increase in organization.

Gaston is forecast to remain in a low-shear environment and
over warm water during the next 24 hours, which should allow for
additional intensification. After that time, the NHC forecast shows
a leveling-off of Gaston's intensity due to the possibility of
upwelling of cooler water resulting from the expected slow motion
of the hurricane. Later in the period, increasing in southwesterly
shear is likely to cause some weakening, but Gaston is predicted to
remain a hurricane during the entire 5-day forecast period.

The forward motion of the hurricane appears to be slowing down
as anticipated, with recent satellite fixes indicating an initial
motion of 325/5 kt. Gaston should continue to decelerate during
the next day or so as it remains within an area of weak steering
flow. In a 2 to 3 days, a mid-latitude trough is forecast to dig
southward off the northeastern United States coast, which should
begin to steer Gaston northeastward, but a a slower speed than that
of typical recurving hurricanes over the North Atlantic. The track
guidance is in good agreement on this scenario, and the NHC track is
near the consensus of the dynamical models.

FORECAST POSITIONS AND MAX WINDS

INIT 28/0900Z 30.1N 54.6W 80 KT 90 MPH
12H 28/1800Z 30.6N 55.0W 90 KT 105 MPH
24H 29/0600Z 31.0N 55.3W 95 KT 110 MPH
36H 29/1800Z 31.3N 55.2W 90 KT 105 MPH
48H 30/0600Z 31.9N 54.3W 90 KT 105 MPH
72H 31/0600Z 33.3N 51.2W 90 KT 105 MPH
96H 01/0600Z 35.8N 46.2W 80 KT 90 MPH
120H 02/0600Z 38.5N 39.5W 70 KT 80 MPH

$$
Forecaster Brown

[Blinhart]

Looks like Gaston will help add some much needed ACE that this season needed. Could become a Cat 3.

[abajan]

I suspect this will impact the Azores, but time will tell.