ATL: GASTON - Post-Tropical - Discussion

[psyclone]

the Atlantic has finally produced the type of storm many said it couldn't...so we know it's got potential if the right conditions present themselves. I'd be shocked if this were the last major this year..

[cycloneye]

HURRICANE GASTON DISCUSSION NUMBER 26
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072016
1100 PM AST SUN AUG 28 2016

Gaston remains a well organized hurricane. Satellite images indicate
that the eye remains quite distinct with a symmetric ring of deep
convection around it. The upper-level outflow is well established
both to the west and the east of the system. The latest Dvorak
classifications from TAFB and SAB are 5.5/102 kt, and automated
values from CIMSS at the University of Wisconsin are 5.9/112 kt.
Based on these data, the initial wind speed is nudged upward to 105
kt.

Gaston has not moved very little during the last several hours. A
continued slow and likely erratic northward motion is forecast
overnight and Monday while Gaston remains in weak steering currents
caused by a blocking mid-level ridge to its northwest. A trough
that is currently over eastern Canada is expected to dampen by the
time it nears Gaston, but it should be strong enough to erode the
ridge and allow the hurricane to become embedded in the mid-latitude
westerlies. This pattern change should result in Gaston's turning
east-northeastward in about 24 hours, with the cyclone continuing in
that direction through the remainder of the forecast period. The
model guidance remains tightly packed, and little change was made to
the previous NHC track prediction.

The atmospheric conditions suggest that Gaston could maintain its
strength for the next day or so, however, given the expected slow
motion of the cyclone there is some chance that cold water upwelling
would counteract that. Beyond that time, the hurricane is
likely to encounter an environment of increasing shear, drier air,
and cooler water. Given these expected conditions, the NHC intensity
forecast shows a gradual weakening trend beginning on Monday. This
prediction is in best agreement with the SHIPS guidance.

FORECAST POSITIONS AND MAX WINDS

INIT 29/0300Z 30.6N 55.2W 105 KT 120 MPH
12H 29/1200Z 30.9N 55.4W 105 KT 120 MPH
24H 30/0000Z 31.4N 54.9W 100 KT 115 MPH
36H 30/1200Z 32.1N 53.5W 95 KT 110 MPH
48H 31/0000Z 33.0N 51.5W 95 KT 110 MPH
72H 01/0000Z 35.5N 46.0W 90 KT 105 MPH
96H 02/0000Z 37.4N 38.7W 75 KT 85 MPH
120H 03/0000Z 37.7N 33.0W 60 KT 70 MPH

$$
Forecaster Cangialosi

[JaxGator]

No one strengthens like Gaston... Man, this is a nice looking and powerful hurricane. It's a good thing it's headed OTS (besides affecting shipping).

[HurricaneRyan]

Quite a pleasant surprise to see this go major.

[CrazyC83]

Since it is forecast to remain farther south, in the 35-36N latitude range and over warmer waters on the recurve, maybe it will make it all the way to the Azores as a hurricane? I know on occasion storms can retain their intensity in that latitude band on the recurve, due to the Gulf Stream split.

[Kazmit]

A well organised piece of eye candy. Best looking storm of the season by a mile.

[StrongWind]

I know this storm is dead to S2K even though it's a Cat3 now. Maybe someone will see this post and be able to help me understand how is it that the 8/29 GFS 00z has Gaston at 1001mb and the NHC has him at 957 mb as of 22:55 EDT. Is the model initialized this far off?

[Hammy]

I know this storm is dead to S2K even though it's a Cat3 now. Maybe someone will see this post and be able to help me understand how is it that the 8/29 GFS 00z has Gaston at 1001mb and the NHC has him at 957 mb as of 22:55 EDT. Is the model initialized this far off?

MSLP on the GFS is really weird and tends to initialize much higher than it actually is, and I'm not quite sure why. Surface pressure (if on Tropical Tidbits) is usually closer to the actual pressure.

[cycloneye]

HURRICANE GASTON DISCUSSION NUMBER 27
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072016
500 AM AST MON AUG 29 2016

Gaston remains a well-organized hurricane. However, the satellite
appearance is slightly less impressive than 6 hours ago, with the
eye becoming less distinct and the deep convection eroding in the
northwestern quadrant. While the various satellite intensity
estimates have changed little since the last advisory, the initial
intensity is lowered to 100 kt based on the degraded appearance.

The hurricane is currently drifting northward. A slow motion is
likely to continue for the next 12 hours or so as Gaston is caught
between two segments of the subtropical ridge. After that time, a
mid-latitude trough moving southeastward from eastern Canada is
expected to weaken the ridge northwest of Gaston, allowing the
cyclone to move generally east-northeastward along the southern edge
of the westerlies. The model guidance remains tightly packed
through 72 hours, and little change was made to the previous
forecast for that time. After 72 hours, the guidance envelope has
shifted a little to the north, and the forecast track was likewise
nudged to stay near the middle of the guidance envelope.

Gaston is expected to remain is a light shear/warm water
environment for the first 24 hours. During this time, the
intensity forecast calls for slight weakening due to dry air
entrainment and the possibility that the slow-moving hurricane will
upwell cold water. After 24 hours, Gaston is likely to move over
decreasing sea surface temperatures and into increasing shear,
which should cause a gradual weakening. The new forecast intensity
is an update of the previous forecast.


FORECAST POSITIONS AND MAX WINDS

INIT 29/0900Z 30.8N 55.2W 100 KT 115 MPH
12H 29/1800Z 31.1N 55.1W 95 KT 110 MPH
24H 30/0600Z 31.8N 54.2W 95 KT 110 MPH
36H 30/1800Z 32.5N 52.5W 95 KT 110 MPH
48H 31/0600Z 33.5N 50.2W 90 KT 105 MPH
72H 01/0600Z 36.5N 44.0W 85 KT 100 MPH
96H 02/0600Z 38.0N 36.5W 70 KT 80 MPH
120H 03/0600Z 38.5N 30.5W 55 KT 65 MPH

$$
Forecaster Beven

[tolakram]

Looks to be recovering from a bout of shear.

http://weather.msfc.nasa.gov/cgi-bin/get-goes?satellite=GOES-E%20HURRICANE&lat=31&lon=-55&info=vis&zoom=1&width=1024&height=768&type=Animation&quality=92&palette=ir1.pal&numframes=5&mapcolor=gray&map=none

[JaxGator]

This is amazing! The Atlantic has and always is capable of doing wonders like this.

https://pbs.twimg.com/media/Cq_9DdkWcAAgH3P.jpg

[Ntxw]

Cloud tops are not as cold as yesterday and it's been having issues with it's eye for some time. I think Gaston may have already peaked but sure was a great satellite storm to see happen in the Atlantic

[cycloneye]

HURRICANE GASTON DISCUSSION NUMBER 28
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072016
1100 AM AST MON AUG 29 2016

Over the past few hours, the satellite presentation of Gaston has
become slightly less organized, with decreasing convection noted in
the eyewall. Satellite estimates are a bit lower, so the initial
wind speed is reduced to 95 kt. Little change in intensity is
expected for the next couple of days while Gaston remains over warm
waters with light-to-moderate shear. Thereafter, a gradual
increase in shear, along with a decrease in SSTs, should cause a
more significant weakening. The latest NHC intensity forecast is
simply an update of the previous one since the guidance continues
to be in fairly good agreement.

Gaston is still drifting northward. The steering currents should
become better defined tomorrow as a ridge becomes established to
the south of the cyclone. The ridge should cause Gaston to
accelerate to the east-northeast over the next few days, although
the cyclone stays south of the main belt of mid-latitude
westerlies. Guidance is coming into better agreement on the system
approaching the Azores in about 5 days, although there are some
speed differences. No significant changes were made to the
previous forecast, which lies near or just south of the model
consensus.

FORECAST POSITIONS AND MAX WINDS

INIT 29/1500Z 31.0N 55.4W 95 KT 110 MPH
12H 30/0000Z 31.3N 55.1W 95 KT 110 MPH
24H 30/1200Z 31.9N 53.7W 95 KT 110 MPH
36H 31/0000Z 32.6N 51.7W 90 KT 105 MPH
48H 31/1200Z 33.7N 49.2W 90 KT 105 MPH
72H 01/1200Z 36.7N 42.5W 80 KT 90 MPH
96H 02/1200Z 38.0N 35.0W 65 KT 75 MPH
120H 03/1200Z 39.0N 30.5W 50 KT 60 MPH

$$
Forecaster Blake

[Kazmit]

Down to 95 kts, a strong Cat 2. Looks like Gaston's already peaked, and what a storm it was. It looks like the Azores could get their second storm by day 5, so it looks like Gaston is a threat to land after all...

[funster]

This headline and story are so wrong: "Hurricane Gaston becomes the first major hurricane of the season and threatens Florida and North Carolina"
http://www.dailymail.co.uk/news/article ... olina.html

A tropical storm warning has been issued for the coasts of North Carolina and Florida
Hurricane Gaston is southeast of Cape Hatteras
The storm should pass offshore of the Outer Banks of North Carolina on Tuesday
Florida officials are worried about the storm dumping water and exacerbating concerns about the Zika virus

what are they smoking?

[AxaltaRacing24]

This headline and story are so wrong: "Hurricane Gaston becomes the first major hurricane of the season and threatens Florida and North Carolina"
http://www.dailymail.co.uk/news/article ... olina.html

A tropical storm warning has been issued for the coasts of North Carolina and Florida
Hurricane Gaston is southeast of Cape Hatteras
The storm should pass offshore of the Outer Banks of North Carolina on Tuesday
Florida officials are worried about the storm dumping water and exacerbating concerns about the Zika virus

what are they smoking?

I've seen it all.

[CrazyC83]

How does it look for the Azores down the line?

[Ntxw]

I know this storm is dead to S2K even though it's a Cat3 now. Maybe someone will see this post and be able to help me understand how is it that the 8/29 GFS 00z has Gaston at 1001mb and the NHC has him at 957 mb as of 22:55 EDT. Is the model initialized this far off?

MSLP on the GFS is really weird and tends to initialize much higher than it actually is, and I'm not quite sure why. Surface pressure (if on Tropical Tidbits) is usually closer to the actual pressure.

It's all from the same source. Are you sure you're not looking further up vs at the surface?

[cycloneye]

 https://twitter.com/philklotzbach/status/770326105106460672

[Ntxw]

14-15 units so far. Another 5 units is not out of the question so near 20 units. Amazing what a major hurricane will do to help ACE and seasonal averages. Even better as a fish.