ATL: GASTON - Post-Tropical - Discussion

[cycloneye]

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

Gaston's satellite presentation continues to slowly degrade, with
the latest microwave data suggesting it could be undergoing an
eyewall replacement. The initial wind speed is lowered to 90 kt in
accordance with the latest satellite estimates. Little change in
intensity is expected for the next couple of days while Gaston
remains over warm waters with light-to-moderate shear, although the
eyewall cycle adds a wrinkle to the forecast. In a couple of days,
a gradual increase in shear, along with a decrease in SSTs, should
cause a more significant weakening. Intensity guidance is a bit
lower than 6 hours ago, and the latest NHC intensity forecast
follows that trend.

Gaston appears to be moving a bit faster, now north-northeastward at
3 kt. Due to a ridge becoming established to the southeast of the
cyclone, Gaston should accelerate to the east-northeast over the
next few days. The end of the forecast is tricky, with some
uncertainties over how Gaston interacts with the mid-latitude
westerlies and the strength of an eastern Atlantic ridge. While
the overall guidance suite has shifted somewhat to the north at days
4 and 5, the ECMWF has been more consistent during the past few
days and has stayed farther south. Thus, the new forecast is on
the southern side of the guidance envelope, to the south of the
model consensus at long range.

FORECAST POSITIONS AND MAX WINDS

INIT 29/2100Z 31.2N 55.2W 90 KT 105 MPH
12H 30/0600Z 31.6N 54.5W 90 KT 105 MPH
24H 30/1800Z 32.2N 52.8W 85 KT 100 MPH
36H 31/0600Z 33.2N 50.7W 85 KT 100 MPH
48H 31/1800Z 34.6N 48.0W 85 KT 100 MPH
72H 01/1800Z 37.7N 39.6W 75 KT 85 MPH
96H 02/1800Z 38.5N 32.0W 55 KT 65 MPH
120H 03/1800Z 40.0N 28.0W 40 KT 45 MPH

$$
Forecaster Blake

[1900hurricane]

I wonder if upwelling is getting to the slow-moving Gaston. Core convection has been on the downswing for a while now, and the waters of the Atlantic north of 30*N can't be that warm to a great depth.

[Kazmit]

From Google Earth. I think this imagery was from earlier today.

[TropicalAnalystwx13]

Perhaps trying to re-intensify this evening.

[1900hurricane]

Yep, looks like Gaston has begun to move again, putting it over fresh waters. It's not weakening any more at the very least.

[cycloneye]

HURRICANE GASTON DISCUSSION NUMBER 30
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072016
1100 PM AST MON AUG 29 2016

The satellite presentation of Gaston has not changed much during
the last several hours. The eye is ragged-looking in infrared
satellite images and recent microwave data indicate that there are
some signs of a double eyewall structure. The initial intensity is
held at 90 kt for this advisory, in agreement with the Dvorak
CI-numbers from TAFB and SAB. Gaston will likely change little in
strength during the next couple of days while it remains in
generally conducive environmental conditions. However, fluctuations
in strength are possible if the cyclone continues to undergo an
eyewall replacement. Beyond a couple of days, steady weakening is
anticipated when the hurricane moves over cooler waters and into an
environment of increasing shear and drier air. The NHC intensity
forecast is largely unchanged from the previous one.

Gaston has turned northeastward and is moving a bit faster, with the
initial motion estimated to be 045/5 kt. A trough currently
seen in water vapor images near Atlantic Canada is expected to
approach Gaston during the next 12 to 24 hours, and that should
cause the hurricane to become embedded in the mid-latitude
westerlies. This should result in Gaston turning east-northeastward
on Tuesday with a steady increase in forward speed during the next
few days. The model guidance has shifted a little to the north this
cycle, and the NHC track forecast has been nudged in that direction.

FORECAST POSITIONS AND MAX WINDS

INIT 30/0300Z 31.6N 54.6W 90 KT 105 MPH
12H 30/1200Z 32.1N 53.6W 85 KT 100 MPH
24H 31/0000Z 32.8N 51.7W 85 KT 100 MPH
36H 31/1200Z 34.0N 49.4W 85 KT 100 MPH
48H 01/0000Z 35.7N 45.9W 85 KT 100 MPH
72H 02/0000Z 39.0N 36.3W 70 KT 80 MPH
96H 03/0000Z 40.0N 29.2W 50 KT 60 MPH
120H 04/0000Z 41.0N 24.8W 40 KT 45 MPH

$$
Forecaster Cangialosi

[cycloneye]

HURRICANE GASTON DISCUSSION NUMBER 31
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072016
500 AM AST TUE AUG 30 2016

Gaston is completing an eyewall replacement cycle and currently
features a well-defined 35 n mi wide eye. The convective clouds
have eroded somewhat west of the eye since the last advisory, and
the various subjective and objective intensity estimates have also
decreased. The initial intensity is thus lowered to 85 kt.

The initial motion is now 055/5. A mid- to upper-level trough
currently seen in water vapor images near Atlantic Canada is
expected to approach Gaston during the next 12 to 24 hours, and that
should cause the hurricane to become embedded in the mid-latitude
westerlies. As a result, Gaston should accelerate generally
east-northeastward through 72 hours. At 96 hours, a building ridge
southwest of Gaston may cause a more easterly motion as the cyclone
approaches the Azores Islands. This should be followed by a
northeastward turn by 120 hours as a second mid-latitude trough
approaches the tropical cyclone. The track guidance generally
agrees with this scenario, although the model spread increases
after 72 hours. The new forecast track is changed little from the
previous track and lies near the center of the guidance envelope.

The intensity guidance suggests that little change in strength is
likely for the next 36-48 hours as Gaston moves over relatively
warm water in a light or moderate westerly shear environment.
After that time, increasing shear and decreasing sea surface
temperatures should cause a steady decay. The new intensity
forecast is an update of the previous forecast in best agreement
with the SHIPS and LGEM models.


FORECAST POSITIONS AND MAX WINDS

INIT 30/0900Z 32.0N 54.0W 85 KT 100 MPH
12H 30/1800Z 32.4N 52.7W 85 KT 100 MPH
24H 31/0600Z 33.4N 50.6W 85 KT 100 MPH
36H 31/1800Z 35.0N 47.7W 85 KT 100 MPH
48H 01/0600Z 36.8N 43.5W 85 KT 100 MPH
72H 02/0600Z 39.5N 34.0W 70 KT 80 MPH
96H 03/0600Z 39.5N 28.5W 50 KT 60 MPH
120H 04/0600Z 42.5N 23.5W 35 KT 40 MPH

$$
Forecaster Beven

[alan1961]

ISS captures Hurricane Gaston with a few camera adjustments

[tolakram]

visible. Big Eye

http://weather.msfc.nasa.gov/cgi-bin/get-goes?satellite=GOES-E%20HURRICANE&lat=32&lon=-53&info=vis&zoom=1&width=1024&height=768&type=Animation&quality=92&palette=ir1.pal&numframes=5&mapcolor=gray&map=none

[tolakram]

Off the FTP site now that GoesE is working again.

[cycloneye]

HURRICANE GASTON DISCUSSION NUMBER 32
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072016
1100 AM AST TUE AUG 30 2016

Microwave satellite images indicate that Gaston has completed an
eyewall replacement cycle. The eye is better defined than it was
overnight and it has contracted some. In addition, the convective
pattern has gained symmetry, and dry slots that were apparent
overnight are no longer evident. The initial intensity is
increased a little to 90 kt, in agreement with a Dvorak
classification of 5.0/90 kt from TAFB and slightly higher numbers
from CIMSS at the University of Wisconsin.

Fluctuations in strength are likely during the next day or so
while Gaston remains in generally conducive environmental
conditions. After that time, the hurricane is expected to move
over progressively cooler waters and into an atmosphere of
increasing shear and dry air. These conditions should cause a
steady weakening trend likely beginning on Wednesday night or
Thursday. The NHC intensity forecast is a little higher than the
previous one in the short term, but is largely unchanged otherwise.
This forecast is in good agreement with the intensity model
consensus.

The initial motion is now 060/7 kt. A mid- to upper-level trough to
the northwest of Gaston should cause the hurricane to become more
embedded in the mid-latitude westerlies. As a result, Gaston will
likely accelerate east-northeastward during the next few days.
By the end of the forecast period, a large extratropical low
pressure area will approach Gaston and it should cause the hurricane
to turn to the northeast and slow down. The NHC track forecast is
a bit slower than the previous one at the longer range points, and
brings a weaker Gaston near the Azores Islands in 3 to 4 days.

FORECAST POSITIONS AND MAX WINDS

INIT 30/1500Z 32.2N 52.9W 90 KT 105 MPH
12H 31/0000Z 32.8N 51.5W 90 KT 105 MPH
24H 31/1200Z 34.1N 49.1W 90 KT 105 MPH
36H 01/0000Z 35.9N 45.6W 85 KT 100 MPH
48H 01/1200Z 37.6N 41.2W 80 KT 90 MPH
72H 02/1200Z 39.0N 32.7W 65 KT 75 MPH
96H 03/1200Z 39.5N 28.2W 45 KT 50 MPH
120H 04/1200Z 42.0N 24.0W 35 KT 40 MPH

$$
Forecaster Cangialosi

[Hurricane_Luis]

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?

Its the Daily Mail. There is not a worse newspaper to read than that. It is a truly awful excuse for journalism, they clearly never proof read.

[1900hurricane]

Hello eye.

[CrazyC83]

If this re-intensifies, this could be trouble for the Azores. Has a major hurricane ever hit the island chain?

[tolakram]

[tolakram]

Live loop from today

http://weather.msfc.nasa.gov/cgi-bin/get-goes?satellite=GOES-E%20HURRICANE&lat=32&lon=-53&info=vis&zoom=1&width=1024&height=768&type=Animation&quality=92&palette=ir1.pal&numframes=16&mapcolor=gray&map=none

[1900hurricane]

Massive eyes are awesome.

[abajan]

If this re-intensifies, this could be trouble for the Azores. Has a major hurricane ever hit the island chain?

Not according to this.

[abajan]

... Has a major hurricane ever hit the island chain?

Not according to this.

[cycloneye]

Very nice and large eye.