EPAC: SEYMOUR - Post-Tropical

[Ntxw]

Been quietly glancing at this system and pretty surprised it got this strong. I hope it does make cat 5 to fit the narrative of the past two big seasons having one and this being the third hyperactive season.

Agree with Yellow Evan symmetry at least at the moment is what he needs to work on

[CrazyC83]

Given that Dvorak usually underestimates small storms and the CMG surrounding the storm, I would personally put it at 140 kt.

[Yellow Evan]

It's also less symmetrical than a typical T6.5 storm.

[Yellow Evan]

Probably at peak intensity at this point.

[Cunxi Huang]

EP, 20, 201610260600, 10, DVTS, CI, , 1620N, 11840W, , 1, 127, 2, , , , , , , , , , , , , , , , , E, SAB, PL, IM, 1, 5565 /////, , , GOES15, LLCC, T, DT=5.5 BO EYE MET=5.5 PT=6.0 FTBO DT

totally expected.

[Cunxi Huang]

EP, 20, 2016102606, , BEST, 0, 162N, 1184W, 125, 946, HU, 34, NEQ, 80, 70, 50, 70, 1010, 140, 10, 0, 0, E, 0, , 0, 0, SEYMOUR, D, 0, , 0, 0, 0, 0, genesis-num, 037,

GOES-15 25/2200Z RGB

[hurricanes1234]

Remains at 130 knots. Continue to be a very beautiful storm.

000
WTPZ45 KNHC 260849
TCDEP5

HURRICANE SEYMOUR DISCUSSION NUMBER 13
NWS NATIONAL HURRICANE CENTER MIAMI FL EP202016
200 AM PDT WED OCT 26 2016

Seymour remains an impressive hurricane in geostationary satellite
pictures, with a very distinct eye surrounded by a symmetric CDO.
Subjective and objective Dvorak current intensity numbers are
unchanged from before and the initial intensity remains 130 kt
for this advisory. Some slight strengthening is still possible
this morning while Seymour remains over warm water and in a low
shear environment, however, by this afternoon the hurricane will
begin moving over slightly lower SSTs, which should start the
weakening process. Seymour is forecast to cross the 26 degree
Celsius isotherm tonight and move over colder waters and into an
area of strong southwesterly wind shear thereafter. These conditions
are expected to cause a very rapid decrease in intensity on
Thursday, and Seymour is forecast to become a tropical storm within
48 hours and degenerate into a post-tropical remnant low on Friday
or early Saturday.

The initial motion estimate is 290/12 kt. A deepening mid- to
upper-level trough seen in water vapor imagery near 140W is expected
to erode the western portion of the ridge that has been steering
Seymour westward during the past few days. As the ridge weakens,
Seymour is forecast to turn northwestward, then northward ahead of
the trough. After 48 hours, Seymour's forward motion should
decrease as it becomes vertically shallow and is steered by the
weaker low-level flow. The latest guidance envelope has shifted
northward and eastward at 36 h and beyond, and the NHC track
forecast has been adjusted accordingly.


FORECAST POSITIONS AND MAX WINDS

INIT 26/0900Z 16.4N 119.0W 130 KT 150 MPH
12H 26/1800Z 17.2N 120.5W 120 KT 140 MPH
24H 27/0600Z 18.6N 121.9W 95 KT 110 MPH
36H 27/1800Z 20.1N 122.5W 75 KT 85 MPH
48H 28/0600Z 21.2N 122.5W 50 KT 60 MPH
72H 29/0600Z 22.0N 122.5W 30 KT 35 MPH...POST-TROP/REMNT LOW
96H 30/0600Z 22.5N 122.5W 20 KT 25 MPH...POST-TROP/REMNT LOW
120H 31/0600Z...DISSIPATED

$$
Forecaster Brown

[bg1]

How many Cat 4s does that make since 2014? A thousand?

[Kazmit]

I bet 150mph will be its peak. But wow, Seymour has really turned out to be a late-season surprise.

[Yellow Evan]

How many Cat 4s does that make since 2014? A thousand?

22 Cat 4/5's in the past three years combined.

[1900hurricane]

[cycloneye]

HURRICANE SEYMOUR DISCUSSION NUMBER 14
NWS NATIONAL HURRICANE CENTER MIAMI FL EP202016
800 AM PDT WED OCT 26 2016

Seymour continues to maintain an impressive central dense overcast,
consisting of very deep convection around a 15 n mi well-defined
eye. However, the distribution of convection has become slightly
asymmetric since the last advisory, with the greatest coverage to
the north and east of the center. The convective asymmetry is
likely indicative of some increase in southwesterly shear. A blend
of the latest Dvorak T- and CI-numbers, including UW-CIMSS ADT
values, is used to lower the initial intensity estimate of 120 kt.

Seymour is living on borrowed time. A large mid- to upper-level
trough seen in water vapor imagery upstream of the cyclone should
cause a considerable increase in southwesterly shear within 24
hours. By that time, Seymour will already have reached much cooler
waters. This should result in weakening, with the rate of filling
only increasing with time. By 36 hours, the shear should become
extremely strong and cause the vortex to shear apart, with the
middle and upper portions of the circulation moving well to the
north or northeast of the low-level center. The official forecast
shows Seymour becoming a post-tropical remnant low in 48 hours in
general agreement with global models that depict this decoupling as
soon as 36 to 42 hours. The NHC intensity forecast shows about the
same rate of weakening as the previous one and is close to the
multi-model consensus.

The initial motion estimate is 290/13. Seymour has begun to gain a
little more latitude recently as it nears the western periphery of a
mid-level ridge west of the Baja California peninsula. The
cyclone's motion should slow and become northwesterly soon and
then shift north-northwestward and northward in 24 to 36 hours as
Seymour becomes embedded in the flow between the high to the
northeast and the trough to the northwest. Once Seymour becomes a
shallow system in 48 hours, the remnant low will slow further and
turn north-northeastward until dissipation. The NHC track forecast
is only slightly to the left of the previous one after 24 hours and
a little faster during the remnant low phase.


FORECAST POSITIONS AND MAX WINDS

INIT 26/1500Z 16.9N 120.2W 120 KT 140 MPH
12H 27/0000Z 18.0N 121.5W 105 KT 120 MPH
24H 27/1200Z 19.7N 122.6W 80 KT 90 MPH
36H 28/0000Z 21.1N 122.9W 60 KT 70 MPH
48H 28/1200Z 22.2N 122.4W 35 KT 40 MPH...POST-TROP/REMNT LOW
72H 29/1200Z 23.7N 121.7W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 30/1200Z...DISSIPATED

$$
Forecaster Kimberlain

[Yellow Evan]

Eye starting to fill in. SSW shear picking up.

[Yellow Evan]

EP, 20, 2016102618, , BEST, 0, 172N, 1207W, 110, 958, HU, 34, NEQ, 80, 70, 50, 70, 1010, 140, 10, 0, 0, E, 0, , 0, 0, SEYMOUR, D, 0, , 0, 0, 0, 0, genesis-num, 037,
EP, 20, 2016102618, , BEST, 0, 172N, 1207W, 110, 958, HU, 50, NEQ, 40, 30, 20, 30, 1010, 140, 10, 0, 0, E, 0, , 0, 0, SEYMOUR, D, 0, , 0, 0, 0, 0, genesis-num, 037,
EP, 20, 2016102618, , BEST, 0, 172N, 1207W, 110, 958, HU, 64, NEQ, 20, 15, 10, 15, 1010, 140, 10, 0, 0, E, 0, , 0, 0, SEYMOUR, D, 0, , 0, 0, 0, 0, genesis-num, 037,

[tolakram]

From the FTP site,

Yesterday, 10/25 at 23:30z. The last good visible and near max strength.

[cycloneye]

HURRICANE SEYMOUR DISCUSSION NUMBER 15
NWS NATIONAL HURRICANE CENTER MIAMI FL EP202016
200 PM PDT WED OCT 26 2016

Seymour has begun to quickly weaken. The hurricane's central dense
overcast has taken on a distorted appearance, and the deep
convection associated with the cyclone's circulation has become
noticeably asymmetric. The eye has also become cloud-filled and
has cooled rather dramatically in the last few hours. The recent
deterioration of the cloud pattern is associated with a considerable
increase of southwesterly shear over the cyclone. Dvorak T-numbers
have decreased to T5.5/102 kt from both satellite agencies, and
these estimates averaged with Dvorak CI-numbers, are used to lower
the initial intensity to 110 kt.

The shear, currently analyzed in the 15 to 20 kt range, is forecast
to increase tremendously over Seymour during the next 24 to 36 hours
as a strong mid- to upper-level tropospheric trough approaches the
cyclone from the west. Since Seymour is a small tropical cyclone and
will be traversing cooler waters by that time, the weakening trend
should become increasingly more rapid. Global models show the vortex
decoupling as a result of the strong deep-layer shear in 30 to 36
hours, and the official forecast shows Seymour degenerating into a
remnant low by 48 hours. The NHC track forecast represents an
update of the previous one and is near the various model consensus
aids.

Seymour continues to gain a greater northward component of motion,
and the initial motion estimate is 300/11. The cyclone is forecast
to turn even more poleward and slow down during the next 24 to 36
hours as it rounds the western periphery of a mid-level high located
west of the Baja California peninsula. While the vortex remains
intact, the strong south-southwesterly flow associated with the
upstream trough should cause Seymour to turn north-northeastward
before shearing off and eventually dissipating. The NHC intensity
forecast is not much different than the previous one and near the
multi-model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT 26/2100Z 17.5N 121.2W 110 KT 125 MPH
12H 27/0600Z 18.8N 122.2W 85 KT 100 MPH
24H 27/1800Z 20.6N 123.0W 60 KT 70 MPH
36H 28/0600Z 22.3N 122.6W 40 KT 45 MPH
48H 28/1800Z 23.5N 121.7W 30 KT 35 MPH...POST-TROP/REMNT LOW
72H 29/1800Z...DISSIPATED

$$
Forecaster Kimberlain

[Yellow Evan]

* EAST PACIFIC SHIPS INTENSITY FORECAST *
* IR SAT DATA AVAILABLE, OHC AVAILABLE *
* SEYMOUR EP202016 10/27/16 00 UTC *

TIME (HR) 0 6 12 18 24 36 48 60 72 84 96 108 120
V (KT) NO LAND 100 85 71 57 43 21 DIS DIS DIS DIS DIS DIS DIS
V (KT) LAND 100 85 71 57 43 21 DIS DIS DIS DIS DIS DIS DIS
V (KT) LGEM 100 87 75 64 54 38 27 DIS DIS DIS DIS DIS DIS
Storm Type TROP TROP TROP TROP TROP TROP TROP N/A N/A N/A N/A N/A N/A

SHEAR (KT) 18 24 27 29 36 43 42 N/A N/A N/A N/A N/A N/A
SHEAR ADJ (KT) 7 8 12 13 10 -4 -3 N/A N/A N/A N/A N/A N/A
SHEAR DIR 228 232 240 231 231 249 256 N/A N/A N/A N/A N/A N/A
SST (C) 26.0 25.5 25.1 24.5 23.9 22.9 22.3 N/A N/A N/A N/A N/A N/A
POT. INT. (KT) 124 118 114 107 101 90 83 N/A N/A N/A N/A N/A N/A
200 MB T (C) -52.9 -53.4 -53.7 -53.8 -53.7 -54.3 -54.4 N/A N/A N/A N/A N/A N/A
200 MB VXT (C) 0.0 0.0 0.0 0.0 0.4 0.3 0.1 N/A N/A N/A N/A N/A N/A
TH_E DEV (C) 7 6 5 4 4 2 2 N/A N/A N/A N/A N/A N/A
700-500 MB RH 55 51 53 49 45 36 28 N/A N/A N/A N/A N/A N/A
MODEL VTX (KT) 21 18 17 16 13 10 6 LOST LOST LOST LOST LOST LOST
850 MB ENV VOR -40 -60 -47 -26 -4 -4 -16 N/A N/A N/A N/A N/A N/A
200 MB DIV 52 64 49 43 19 -3 -13 N/A N/A N/A N/A N/A N/A
700-850 TADV 2 3 3 4 2 12 2 N/A N/A N/A N/A N/A N/A
LAND (KM) 1192 1190 1176 1108 1046 876 731 N/A N/A N/A N/A N/A N/A
LAT (DEG N) 18.2 19.1 19.9 20.8 21.7 23.2 24.3 N/A N/A N/A N/A N/A N/A
LONG(DEG W) 121.4 122.1 122.7 122.8 122.9 122.1 121.2 N/A N/A N/A N/A N/A N/A
STM SPEED (KT) 11 10 9 9 9 7 7 N/A N/A N/A N/A N/A N/A
HEAT CONTENT 1 0 0 0 0 0 0 0 0 0 0 0 0

FORECAST TRACK FROM OFCI INITIAL HEADING/SPEED (DEG/KT):320/ 12 CX,CY: -7/ 9
T-12 MAX WIND: 125 PRESSURE OF STEERING LEVEL (MB): 623 (MEAN=586)
GOES IR BRIGHTNESS TEMP. STD DEV. 50-200 KM RAD: 14.0 (MEAN=14.5)
% GOES IR PIXELS WITH T < -20 C 50-200 KM RAD: 80.0 (MEAN=65.0)
PRELIM RI PROB (DV .GE. 30 KT IN 24 HR): 0.0

INDIVIDUAL CONTRIBUTIONS TO INTENSITY CHANGE
6 12 18 24 36 48 60 72 84 96 108 120
----------------------------------------------------------
SAMPLE MEAN CHANGE 0. 0. 1. 1. 1. 1. 1. 1. 0. -1. -1. -2.
SST POTENTIAL -2. -6. -10. -16. -28. -38. -44. -48. -51. -53. -53. -55.
VERTICAL SHEAR MAG -3. -7. -12. -16. -21. -24. -24. -24. -24. -26. -31. -36.
VERTICAL SHEAR ADJ -1. -1. -3. -4. -4. -3. -3. -2. -2. -1. -1. -2.
VERTICAL SHEAR DIR 0. -1. -1. -1. 0. 1. 1. 1. 1. 1. 1. 1.
PERSISTENCE -7. -10. -10. -10. -7. -3. -1. 1. 2. 3. 5. 6.
200/250 MB TEMP. 0. 0. 0. 0. 0. 1. 1. 1. 1. 2. 2. 2.
THETA_E EXCESS 0. 0. 0. -1. -2. -3. -4. -5. -5. -6. -7. -7.
700-500 MB RH 0. 0. 0. -1. -1. -2. -3. -4. -5. -5. -6. -6.
MODEL VTX TENDENCY -1. -2. -4. -8. -14. -19. -20. -21. -20. -20. -18. -17.
850 MB ENV VORTICITY 0. 0. 0. 0. 0. 1. 1. 2. 2. 2. 2. 3.
200 MB DIVERGENCE 0. 0. 0. 0. 0. -1. -1. -2. -2. -1. -1. -1.
850-700 T ADVEC 0. 0. 0. 0. 0. 0. 1. 1. 1. 2. 2. 3.
ZONAL STORM MOTION 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
STEERING LEVEL PRES 0. 0. 0. 0. 0. 1. 1. 1. 1. 1. 1. 1.
DAYS FROM CLIM. PEAK 0. 0. 0. 0. 0. 0. 0. -1. -1. -2. -2. -2.
GOES PREDICTORS -1. -2. -3. -4. -4. -2. -1. 0. 1. 3. 3. 3.
OCEAN HEAT CONTENT 0. 0. -1. -1. -1. -2. -1. -1. -1. 0. 0. 0.
----------------------------------------------------------
TOTAL CHANGE -15. -29. -43. -57. -79. -93. -96. -98.-101.-102.-105.-109.

CURRENT MAX WIND (KT): 100. LAT, LON: 18.2 121.4

** 2015 E. Pacific RI INDEX EP202016 SEYMOUR 10/27/16 00 UTC **
(SHIPS-RII PREDICTOR TABLE for 30 KT OR MOREMAXIMUM WIND INCREASE IN NEXT 24-h)

Predictor Value RI Predictor Range Scaled Value(0-1) % Contribution
12 HR PERSISTENCE (KT): -25.0 -22.0 to 38.5 0.00 0.0
POT = MPI-VMAX (KT) : 12.9 40.3 to 144.5 0.00 0.0
HEAT CONTENT (KJ/cm2) : 0.2 0.0 to 75.9 0.00 999.0
STD DEV OF IR BR TEMP : 14.0 38.9 to 2.1 0.68 999.0
850-200 MB SHEAR (KT) : 26.8 18.9 to 1.4 0.00 0.0
MAXIMUM WIND (kt) : 100.0 22.5 to 132.0 0.43 999.0
D200 (10**7s-1) : 45.4 -11.0 to 135.3 0.39 999.0
BL DRY-AIR FLUX (w/m2): 745.4 638.0 to -68.2 0.00 0.0
2nd PC OF IR BR TEMP : -1.6 2.1 to -1.7 0.97 999.0
% AREA WITH TPW <45 mm: 0.0 81.4 to 0.0 1.00 999.0

SHIPS Prob RI for 20kt/ 12hr RI threshold= 0% is 0.0 times sample mean ( 6.3%)
SHIPS Prob RI for 25kt/ 24hr RI threshold= 0% is 0.0 times sample mean (12.9%)
SHIPS Prob RI for 30kt/ 24hr RI threshold= 0% is 0.0 times sample mean ( 8.6%)
SHIPS Prob RI for 35kt/ 24hr RI threshold= 0% is 0.0 times sample mean ( 5.8%)
SHIPS Prob RI for 40kt/ 24hr RI threshold= 0% is 0.0 times sample mean ( 4.1%)
SHIPS Prob RI for 45kt/ 36hr RI threshold= 0% is 0.0 times sample mean ( 7.1%)
SHIPS Prob RI for 55kt/ 48hr RI threshold= 0% is 0.0 times sample mean ( 5.9%)

Matrix of RI probabilities
---------------------------------------------------------------------
RI (kt / h) | 20/12 | 25/24 | 30/24 | 35/24 | 40/24 | 45/36 | 55/48
---------------------------------------------------------------------
SHIPS-RII: 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
Logistic: 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
Bayesian: 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
Consensus: 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%

## ANNULAR HURRICANE INDEX (AHI) EP202016 SEYMOUR 10/27/16 00 UTC ##
## STORM NOT ANNULAR, SCREENING STEP FAILED, NPASS=3 NFAIL=4 ##
## AHI= 0 (AHI OF 100 IS BEST FIT TO ANN. STRUC., 1 IS MARGINAL, 0 IS NOT ANNULAR) ##

[cycloneye]

HURRICANE SEYMOUR DISCUSSION NUMBER 16
NWS NATIONAL HURRICANE CENTER MIAMI FL EP202016
800 PM PDT WED OCT 26 2016

Seymour is weakening rapidly. Although a small eye was still
apparent in microwave data a few hours ago, this feature is no
longer evident in the latest geostationary satellite images. In
addition, the convective pattern has become asymmetric due to
increasing southwesterly shear. The initial wind speed is lowered to
95 kt based on Dvorak final T- and CI-numbers from TAFB, SAB, and
CIMSS at the University of Wisconsin. The hurricane is moving
across the 26 deg C isotherm and it is expected to move over even
colder waters during the next couple of days. These unfavorable
oceanic conditions combined with drier air and a significant
increase in wind shear should cause Seymour to continue to rapidly
weaken. The NHC intensity forecast shows a very fast weakening
trend, predicting Seymour to fall below hurricane strength on
Thursday and degenerate to a remnant low on Friday. This forecast
lies near the middle of the intensity guidance envelope.

The hurricane has made the expected turn to the northwest, and is
now moving 320 degrees at 12 kt. A large deep-layer trough
located several hundred miles offshore of the U.S. west coast is
expected to move eastward, causing Seymour to slow down and turn
northward and then northeastward during the next couple of days.
The track models are in good agreement, and the NHC track forecast
lies near the various consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT 27/0300Z 18.7N 121.7W 95 KT 110 MPH
12H 27/1200Z 20.1N 122.5W 75 KT 85 MPH
24H 28/0000Z 21.8N 122.7W 55 KT 65 MPH
36H 28/1200Z 23.2N 122.0W 35 KT 40 MPH...POST-TROPICAL
48H 29/0000Z 24.3N 121.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 30/0000Z...DISSIPATED

$$
Forecaster Cangialosi

[hurricanes1234]

000
WTPZ45 KNHC 270837
TCDEP5

HURRICANE SEYMOUR DISCUSSION NUMBER 17
NWS NATIONAL HURRICANE CENTER MIAMI FL EP202016
200 AM PDT THU OCT 27 2016

Cool waters and strong southwesterly shear are causing Seymour to
rapidly weaken this morning. The cloud pattern of the tropical
cyclone is becoming increasingly asymmetric, with the center
located near the southwestern edge of the main convective mass. As
a result of the degradation of the cloud pattern, subjective and
objective Dvorak T- and CI-numbers are quickly decreasing, and the
initial intensity has been reduced to 80 kt for this advisory.

Seymour will be moving over SSTs below 25 degrees Celsius and
into an area of vertical shear greater than 30 kt within 12 hours.
These hostile conditions will cause a rapid decrease in wind speed
during the next 24 to 36 hours, and Seymour is predicted to weaken
to a tropical storm this afternoon, and become a post-tropical
remnant low by Friday afternoon.

The hurricane has turned north-northwestward, and is moving 335
degrees at 10 kt. Seymour is forecast to turn northward today, and
then northeastward on Friday ahead of a large deep-layer trough
located well offshore of the west coast of the United States. The
track guidance remains tightly clustered but has trended slightly
faster this cycle. The updated NHC track forecast has been
adjusted accordingly and lies near the multi-model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT 27/0900Z 19.5N 122.1W 80 KT 90 MPH
12H 27/1800Z 21.0N 122.6W 60 KT 70 MPH
24H 28/0600Z 22.6N 122.2W 40 KT 45 MPH
36H 28/1800Z 24.0N 121.2W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 29/0600Z 25.3N 120.0W 20 KT 25 MPH...POST-TROP/REMNT LOW
72H 30/0600Z...DISSIPATED

$$
Forecaster Brown

[wxman57]

Seymour is getting ripped apart by shear now. No way it's a hurricane now. It won't be around much longer.