ATL: GASTON - Post-Tropical - Discussion

[tolakram]

Come on Gaston, time to push up the seasonal ACE.

http://weather.msfc.nasa.gov/cgi-bin/get-goes?satellite=GOES-E%20HURRICANE&lat=30&lon=-54&info=vis&zoom=1&width=1024&height=768&type=Animation&quality=92&palette=ir1.pal&numframes=5&mapcolor=gray&map=none

[cycloneye]

Yeah up to 90kts. 12z Best Track.

Location: 30.3°N 54.7°W
Maximum Winds: 90 kt Gusts: N/A
Minimum Central Pressure: 970 mb
Environmental Pressure: 1016 mb
Radius of Circulation: 180 NM
Radius of Maximum Wind: 15 NM
Eye Diameter: N/A

[tolakram]

[Kazmit]

Wow, Gaston is really rapidly intensifying. Up to 90 kts/105 mph- cat 2. If it continues at this rate we'll have a major on our hands by tonight.

[Ntxw]

It's still working on the eye but overall looks pretty good. T numbers should be well above 5.0 if the process can complete and cloud tops remain cold and be a major

UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.2.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 28 AUG 2016 Time : 124500 UTC
Lat : 30:12:29 N Lon : 54:46:33 W


CI# /Pressure/ Vmax
5.1 / 967.9mb/ 92.4kt


Final T# Adj T# Raw T#
5.0 4.6 5.0

Center Temp : -53.8C Cloud Region Temp : -64.9C

Scene Type : EMBEDDED CENTER CLOUD REGION

Positioning Method : SPIRAL ANALYSIS

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : CKZ Method

Tno/CI Rules : Constraint Limits : 0.7T/6hr
Weakening Flag : ON
Rapid Dissipation Flag : OFF

[CrazyC83]

TXNT24 KNES 281205
TCSNTL

A. 07L (GASTON)

B. 28/1145Z

C. 30.3N

D. 54.7W

E. ONE/GOES-E

F. T5.5/5.5/D2.0/24HRS

G. IR/EIR

H. REMARKS...OW EYE EMBEDDED IN LG AND SURROUNDED BY B FOR DT=5.5.
MET=4.5 WITH PT=5.0. FT IS BASED ON DT.

I. ADDL POSITIONS

NIL


...SALEMI

[CrazyC83]

Based on that latest estimate, I would probably go 95 kt. Doesn't seem quite organized enough yet to be a major.

[cycloneye]

HURRICANE GASTON DISCUSSION NUMBER 24
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072016
1100 AM AST SUN AUG 28 2016

The eye was fairly distinct a few hours ago, but recently it has
become slightly cloud-filled and the inner-core convection has
become less symmetrical. The current intensity is set at 90 kt,
in agreement with a Dvorak estimate from TAFB and objective ADT
values from UW-CIMSS. Assuming the slight degradation of the inner
core structure to be temporary, a little more strengthening is
expected within the next 12 to 24 hours. Gaston should remain in a
low to moderate vertical wind shear environment for the next
couple of days, which would allow the hurricane to more or less
maintain its intensity through 36-48 hours. By 72 hours and beyond,
increasing westerly shear should induce weakening. The official
intensity forecast is close to the multi-model consensus IVCN.

Steering currents are weak, and the initial motion is a
northwestward drift or 320/4 kt. Gaston's motion is being
partially blocked by a narrow subtropical ridge, and this scenario
should continue for the next day or so. The hurricane is expected
to gradually work its way through the ridge and, in 24 to 48 hours,
begin to move northeastward and east-northeastward as it enters the
mid-latitude westerlies. The official forecast is close to a
consensus of the ECMWF and GFS solutions.

FORECAST POSITIONS AND MAX WINDS

INIT 28/1500Z 30.5N 54.8W 90 KT 105 MPH
12H 29/0000Z 30.8N 55.3W 95 KT 110 MPH
24H 29/1200Z 31.2N 55.6W 95 KT 110 MPH
36H 30/0000Z 31.6N 55.1W 90 KT 105 MPH
48H 30/1200Z 32.4N 53.7W 90 KT 105 MPH
72H 31/1200Z 34.3N 49.4W 80 KT 90 MPH
96H 01/1200Z 36.5N 44.0W 75 KT 85 MPH
120H 02/1200Z 38.5N 36.5W 70 KT 80 MPH

$$
Forecaster Pasch

[cycloneye]

Very impressive.

 https://twitter.com/Wx_Geek/status/769949143892647936

[CrazyC83]

At least on visible that looks close to T6.0, although the black ring only goes about halfway around. 105 kt would be my best estimate.

[tolakram]

Took a while bit it looks like it will make it to major.

live visible

http://weather.msfc.nasa.gov/cgi-bin/get-goes?satellite=GOES-E%20HURRICANE&lat=30&lon=-54&info=vis&zoom=1&width=1024&height=768&type=Animation&quality=92&palette=ir1.pal&numframes=5&mapcolor=gray&map=none

[northjaxpro]

Wow. Gaston has that classical look to it now. I think this is now a major hurricane imo.

[Yellow Evan]

Once this finishes off the B ring and/or gets a WMG eye, this will be eligible for a T5.5.

[Yellow Evan]

----- Current Analysis -----
Date : 28 AUG 2016 Time : 174500 UTC
Lat : 30:34:19 N Lon : 54:59:51 W


CI# /Pressure/ Vmax
5.6 / 958.0mb/104.6kt


Final T# Adj T# Raw T#
5.6 5.9 5.9

Estimated radius of max. wind based on IR : 19 km

Center Temp : +4.5C Cloud Region Temp : -63.0C

Scene Type : EYE

[Blinhart]

So this should be a Cat. 3 with winds around 120 if those T nos. are correct?

[Extratropical94]

So this should be a Cat. 3 with winds around 120 if those T nos. are correct?

Yes, 120 mph would be reasonable. The current best track data upgrades Gaston to a major with a slightly lower wind speed of 115 mph / 100 kt.

07L GASTON 160828 1800 30.6N 55.0W ATL 100 962

[TheStormExpert]

Our first major hurricane of the season. YAY!

[cycloneye]

Major cane at 18z Best Track:

Location: 30.6°N 55.0°W
Maximum Winds: 100 kt Gusts: N/A
Minimum Central Pressure: 962 mb
Environmental Pressure: 1016 mb
Radius of Circulation: 180 NM
Radius of Maximum Wind: 15 NM

[cycloneye]

BULLETIN
HURRICANE GASTON ADVISORY NUMBER 25
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072016
500 PM AST SUN AUG 28 2016

...GASTON STRENGTHENS INTO THE FIRST MAJOR HURRICANE OF THE
SEASON...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...30.8N 55.1W
ABOUT 580 MI...935 KM E OF BERMUDA
MAXIMUM SUSTAINED WINDS...115 MPH...185 KM/H
PRESENT MOVEMENT...NW OR 320 DEGREES AT 5 MPH...7 KM/H
MINIMUM CENTRAL PRESSURE...962 MB...28.41 INCHES


HURRICANE GASTON DISCUSSION NUMBER 25
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072016
500 PM AST SUN AUG 28 2016

The 15 n mi diameter eye has become more distinct on visible
satellite images today, and enhanced IR images show a cooling of the
cloud tops surrounding the eye. These features indicate
strengthening, and the current intensity is increased to 100 kt in
agreement with the subjective Dvorak estimates from TAFB and SAB, as
well as objective ADT numbers from UW-CIMSS. Upper-level outflow is
well-established both to the west and the east of the hurricane.
Based on a consensus of the intensity models, not much additional
strengthening is anticipated. When Gaston moves to a little higher
latitude, westerly shear on the system should increase, and steady
weakening is expected to commence in about 48 hours.

Gaston continues to crawl northwestward while being partially
blocked by a narrow mid-level subtropical ridge. The hurricane is
forecast to work its way through the ridge over the next day or so.
By Tuesday, an east-northeastward motion with gradual acceleration
is likely as the system begins to feel the effect of the
mid-latitude westerlies. The official forecast track is shifted a
little southward late in the forecast period, in line with the
latest global model guidance.

FORECAST POSITIONS AND MAX WINDS

INIT 28/2100Z 30.8N 55.1W 100 KT 115 MPH
12H 29/0600Z 31.0N 55.5W 100 KT 115 MPH
24H 29/1800Z 31.4N 55.5W 100 KT 115 MPH
36H 30/0600Z 32.0N 54.4W 95 KT 110 MPH
48H 30/1800Z 32.8N 52.6W 95 KT 110 MPH
72H 31/1800Z 34.9N 47.7W 85 KT 100 MPH
96H 01/1800Z 37.5N 40.5W 75 KT 85 MPH
120H 02/1800Z 37.5N 33.5W 60 KT 70 MPH

$$
Forecaster Pasch

[cycloneye]

...GASTON STRENGTHENS INTO THE FIRST MAJOR HURRICANE OF THE
SEASON...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...30.8N 55.1W
ABOUT 580 MI...935 KM E OF BERMUDA
MAXIMUM SUSTAINED WINDS...115 MPH...185 KM/H
PRESENT MOVEMENT...NW OR 320 DEGREES AT 5 MPH...7 KM/H
MINIMUM CENTRAL PRESSURE...962 MB...28.41 INCHES