ATL: GASTON - Post-Tropical - Discussion

[Hurricaneman]

This is looking like its going to be a powerful hurricane, hope it stays away from Bermuda

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[HurricaneRyan]

Hoping this becomes more than just a Category 1 hurricane.

[AutoPenalti]

As long as it tracks east of Bermuda it can become annular and grow one of those huge demonic pentagram eyes for all I care.

This could be a Cat 6 with 2 eyes that blink and 345 knot winds at the surface for all I care, as long as it stays over open waters.

[cycloneye]

TROPICAL STORM GASTON DISCUSSION NUMBER 3
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072016
500 AM AST TUE AUG 23 2016

Thunderstorm activity has continued to become better organized since
the previous advisory, especially in the inner-core region. In
addition, a 0556Z GPM microwave overpass indicated that a
15-20-nmi-diameter, closed low-level eye feature had developed. The
initial intensity as been increased to 45 kt based on a consensus
Dvorak satellite intensity estimate of T3.0/45 kt from TAFB and SAB,
which is supported by a UW-CIMSS ADT value of T2.9/43 kt.

The initial motion estimate is 290/17 kt. Gaston is expected to
move west-northwestward for the next 72 hours along the southern
periphery of a deep-layer ridge located to the north and northeast
of the cyclone. After that time, a gradual turn toward the
northwest is forecast as Gaston moves into a break in the
subtropical ridge. The models are in excellent agreement on this
track scenario and are closely packed through day 3, with a large
spread in the model tracks occurring after that time due to
differences in the timing of when Gaston will make the poleward turn
through the break in the ridge. The official forecast is similar
to the previous advisory track, and lies a little to the left of the
consensus model TVCN.

The aforementioned eye feature, in conjunction with low shear
conditions, well-defined upper-level anticyclonic outflow, SSTs
near 28 deg C, and mid-level humidity values near 70 percent,
generally would support a period of rapid intensification for the
next 24 hours or so. However, the current forecast follows the trend
of the previous advisory and shows strengthening at a more typical
rate of 20 kt/24h for the next 36 hours due to a narrow band of dry
air that appears to have penetrated into the inner core, which will
take some time to mix out. After that time, the intensity is
leveled off due to the cyclone moving through a band of strong
southwesterly vertical wind shear, which should disrupt both the
convective and upper-level outflow patterns. The initial intensity
is near the IVCN intensity consensus model through 24 hours, and
then a little above that and near the SHIPS model. However, the
new intensity forecast lies well below the GFS model output, which
is forecasting Gaston to become a major hurricane around 120 hours.

FORECAST POSITIONS AND MAX WINDS

INIT 23/0900Z 13.2N 32.4W 45 KT 50 MPH
12H 23/1800Z 13.9N 34.8W 55 KT 65 MPH
24H 24/0600Z 15.2N 37.9W 65 KT 75 MPH
36H 24/1800Z 16.8N 40.6W 75 KT 85 MPH
48H 25/0600Z 18.5N 43.0W 80 KT 90 MPH
72H 26/0600Z 22.6N 47.4W 80 KT 90 MPH
96H 27/0600Z 26.5N 51.5W 80 KT 90 MPH
120H 28/0600Z 29.4N 53.6W 80 KT 90 MPH

$$
Forecaster Stewart

[Kazmit]

Gaston undergoing rapid intensification...

The aforementioned eye feature, in conjunction with low shear
conditions, well-defined upper-level anticyclonic outflow, SSTs
near 28 deg C, and mid-level humidity values near 70 percent,
generally would support a period of rapid intensification for the
next 24 hours or so. However, the current forecast follows the trend
of the previous advisory and shows strengthening at a more typical
rate of 20 kt/24h for the next 36 hours due to a narrow band of dry
air that appears to have penetrated into the inner core, which will
take some time to mix out. After that time, the intensity is
leveled off due to the cyclone moving through a band of strong
southwesterly vertical wind shear, which should disrupt both the
convective and upper-level outflow patterns. The initial intensity
is near the IVCN intensity consensus model through 24 hours, and
then a little above that and near the SHIPS model. However, the
new intensity forecast lies well below the GFS model output, which
is forecasting Gaston to become a major hurricane around 120 hours.

[Kazmit]

Long term models from Wunderground. Shows a NW track before a sharp recurve east of Bermuda.

[cycloneye]

Intensity going up fast. Up to 55kts on 12z Best Track.

AL, 07, 2016082312, , BEST, 0, 135N, 337W, 55, 1002, TS

[cycloneye]

Impressive.

[NotoSans]

Seems to be developing rapidly with a banding-typed eye becoming evident. SAB goes with T4.0/4.0 at 12Z.

TXNT24 KNES 231237
TCSNTL

A. 07L (GASTON)

B. 23/1145Z

C. 13.5N

D. 33.3W

E. ONE/GOES-E

F. T4.0/4.0/D2.0/24HRS

G. IR/EIR/VIS/SSMIS

H. REMARKS...ANIMATED IMAGERY SUGGESTS POSSIBLE BANDING TYPE EYE WHICH
IS VERIFIED IN RECENT SSMIS 37 GHZ DATA. CALCULATING THE DT USING BANDING
RESULTS IN A 3.0 BASED ON 7/10. ASSUMING AN OW EYE SURROUNDED BY...AND
EMBEDDED IN...DG RESULTS IN A DT OF 4.5 WITH NO EYE ADJUSTMENT. PT IS
4.0. MET IS 3.5 BASED ON RAPID DEVELOPMENT OVER THE LAST 24 HOURS. FT
IS BASED ON PT DUE TO UNCERTAINTY IN THE DT CALCULATION.

I. ADDL POSITIONS

23/0625Z 13.1N 31.7W SSMIS
23/0853Z 13.2N 32.5W SSMIS


...TURK

[abajan]

As long as it tracks east of Bermuda it can become annular and grow one of those huge demonic pentagram eyes for all I care.

This could be a Cat 6 with 2 eyes that blink and 345 knot winds at the surface for all I care, as long as it stays over open waters.

A hurricane that powerful would be problematic whether it's a fish or not, because the swells generated would be biblical.

[Kazmit]

I think the NHC should raise the predicted intensity to at least 100mph by the 11am advisory. Gaston's undergoing rapid intensification, and is already a mid/high end TS, and has an eye. We shall see what happens.

[RL3AO]

I was surprised they kept it at 80kt peak for the first few advisories. This has cat 3/4 written all over it IMO.

[CrazyC83]

Given that Dvorak estimate and others, I would say 60 kt right now. As for a peak intensity, I'd go up to 100 kt then level it out at day 5 (and raise afterward).

[cycloneye]

Look at that eye popping out.

[AdamFirst]

It's nice to get an ACE-pumping monster out in the middle of nowhere so it doesn't hurt anyone. Makes for good photogenic hurricanes.

[NotoSans]

NHC now calls for a borderline cat.2 hurricane. Looks like they're closely following the SHIPS guidance.

FORECAST POSITIONS AND MAX WINDS

INIT 23/1500Z 13.8N 34.6W 55 KT 65 MPH
12H 24/0000Z 14.6N 36.9W 65 KT 75 MPH
24H 24/1200Z 16.1N 39.9W 75 KT 85 MPH
36H 25/0000Z 17.8N 42.4W 85 KT 100 MPH
48H 25/1200Z 19.8N 44.6W 80 KT 90 MPH
72H 26/1200Z 24.2N 48.9W 75 KT 85 MPH
96H 27/1200Z 27.7N 52.5W 75 KT 85 MPH
120H 28/1200Z 30.7N 53.5W 80 KT 90 MPH

[cycloneye]

TROPICAL STORM GASTON DISCUSSION NUMBER 4
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072016
1100 AM AST TUE AUG 23 2016

Gaston continues to intensify. The cyclone's cloud pattern has been
gradually transitioning from a curved-band pattern to a central
dense overcast (CDO). Within the formative CDO, a ragged eye-type
feature has occasionally been evident during the last few hours. A
satellite classification of T3.5 is used to increase in the initial
intensity estimate to 55 kt, in agreement with the latest UW-CIMSS
ADT values.

Only light vertical wind shear is forecast to affect Gaston during
the next 24 to 36 hours while the cyclone moves over marginally
warm waters and through a generally moist environment. These
factors suggest that further intensification is likely during this
period of time. By 48 hours, Gaston should encounter increasing
southwesterly to westerly flow at upper-levels associated with a
potent trough over the east-central Atlantic. In the very least,
the forecast shear and a drier atmosphere associated with this
feature should result in an arrested development phase, if not
weakening. Late in the forecast period, global models indicate a
reduction of the shear while Gaston is over warmer waters of 29 deg
C, which could allow for some re-strengthening. Through 36 hours,
the NHC intensity forecast is a bit above the multi-model consensus
and closest to the FSU Superensemble output and the LGEM. After that
time, the forecast trends toward the multi-model consensus.

The initial motion estimate is 285/18. Gaston is being steered
quickly toward the west-northwest around the western extension of
a mid-level subtropical ridge extending westward from North Africa.
The ridge's orientation begins to change as Gaston approaches a
significant break in the subtropical ridge in the central Atlantic,
which results in a northwestward heading and a reduction in
forward speed during the next few days. A northward turn with an
even greater decrease in forward speed is expected by 120 hours
once Gaston enters the weakness over the central Atlantic. The
latest NHC track forecast is largely similar to the previous one
and close to the model consensus aids.




FORECAST POSITIONS AND MAX WINDS

INIT 23/1500Z 13.8N 34.6W 55 KT 65 MPH
12H 24/0000Z 14.6N 36.9W 65 KT 75 MPH
24H 24/1200Z 16.1N 39.9W 75 KT 85 MPH
36H 25/0000Z 17.8N 42.4W 85 KT 100 MPH
48H 25/1200Z 19.8N 44.6W 80 KT 90 MPH
72H 26/1200Z 24.2N 48.9W 75 KT 85 MPH
96H 27/1200Z 27.7N 52.5W 75 KT 85 MPH
120H 28/1200Z 30.7N 53.5W 80 KT 90 MPH

$$
Forecaster Kimberlain

[Ntxw]

Should be a picturesque storm once mature. Pretty steady strengthening, if the eye can clear with colder tops, easily a major

ADT

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

----- Current Analysis -----
Date : 23 AUG 2016 Time : 141500 UTC
Lat : 13:43:47 N Lon : 34:23:07 W


CI# /Pressure/ Vmax
3.5 / 999.4mb/ 55.0kt


Final T# Adj T# Raw T#
3.5 3.5 3.5

Center Temp : -36.8C Cloud Region Temp : -52.7C

Scene Type : IRREGULAR CDO*

Positioning Method : FORECAST INTERPOLATION

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

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : OFF
Rapid Dissipation Flag : OFF

[bg1]

Look at that eye popping out.

http://oi63.tinypic.com/fxa145.jpg

Looks rather small, too... Interesting next couple of days.

[Kazmit]

Impressive indeed. SAT presentation reminds me of a Western Pacific storm.