WPAC: CHAN-HOM - Post-Tropical

[cycloneye]

WDPN31 PGTW 061500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W (CHAN-HOM) WARNING
NR 25//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON (TY) 09W (CHAN-HOM), LOCATED APPROXIMATELY 825 NM
SOUTHEAST OF KADENA AB, HAS TRACKED WEST-NORTHWESTWARD AT 14 KNOTS
OVER THE PAST SIX HOURS. ANIMATED IR IMAGERY DEPICTS A SLIGHT
IMPROVEMENT IN ORGANIZATION WITH A MARKED INCREASE IN CENTRAL
CONVECTION. A 061140Z METOP-B IMAGE AND A 060949Z SSMIS IMAGE REVEAL
TIGHTLY-CURVED CONVECTIVE BANDING WRAPPING INTO A DEFINED CENTER,
THEREFORE, THERE IS GOOD CONFIDENCE IN THE CURRENT POSITION. THE
CURRENT INTENSITY IS ASSESSED AT 65 KNOTS BASED ON THE IMPROVED
STRUCTURE, WHICH IS CONSISTENT WITH THE HIGHER RANGE OF DVORAK
CURRENT INTENSITY ESTIMATES. UPPER-LEVEL ANALYSIS INDICATES THAT TY
09W IS LOCATED IN A FAVORABLE ENVIRONMENT WITH LOW VWS AND NEAR-
RADIAL OUTFLOW, ENHANCED BY A TUTT CELL TO THE NORTHEAST. TY 09W IS
TRACKING ALONG THE SOUTHERN PERIPHERY OF THE DEEP-LAYERED STR.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TY 09W IS FORECAST TO CONTINUE TRACKING WEST-NORTHWESTWARD
UNDER THE STEERING INFLUENCE OF THE STR ENTRENCHED TO THE NORTH.
DYNAMIC GUIDANCE IS IN TIGHT AGREEMENT THROUGH TAU 72 WITH A SPREAD
OF 90 NM IN SOLUTIONS AT TAU 72. ADDITIONALLY, ENSEMBLE GUIDANCE
ALSO INDICATES A HIGH PROBABILITY TRACK COINCIDENT WITH THE JTWC
FORECAST TRACK. TY 09W IS FORECAST TO INTENSIFY STEADILY THROUGH TAU
72 TO A PEAK INTENSITY OF 130 KNOTS DUE TO FAVORABLE CONDITIONS.
C. AFTER TAU 72, TY 09W WILL CONTINUE TO TRACK WEST-NORTHWESTWARD
TO NORTHWESTWARD UNDER THE INFLUENCE OF THE DOMINANT STEERING STR.
VWS AND UPPER-LEVEL DIVERGENCE WILL REMAIN FAVORABLE THROUGH THE END
OF THE FORECAST PERIOD; HOWEVER, COOLER SST AND LOWER OHC VALUES, AS
WELL AS LAND INTERACTION AFTER TAU 96, WILL SERVE TO WEAKEN THE
SYSTEM. DYNAMIC MODEL GUIDANCE DIVERGES AFTER TAU 72, HOWEVER, THE
BULK OF THE GUIDANCE IS IN GOOD AGREEMENT WITH A TRACK NORTH OF
TAIWAN. NAVGEM CONTINUES TO TURN THE SYSTEM ERRONEOUSLY NORTHWARD,
DIRECTLY INTO THE STR, THEREFORE, IS SUSPECT. OVERALL, THERE IS HIGH
CONFIDENCE IN THE JTWC FORECAST TRACK.//
NNNN

[euro6208]

000
WTPQ31 PGUM 061452
TCPPQ1

BULLETIN
TYPHOON CHAN-HOM (09W) ADVISORY NUMBER 25
NATIONAL WEATHER SERVICE TIYAN GU WP092015
200 AM CHST TUE JUL 7 2015

...CHAN-HOM NOW A TYPHOON...

CHANGES WITH THIS ADVISORY
--------------------------
NONE.

WATCHES AND WARNINGS
--------------------
NONE.

SUMMARY OF 100 AM CHST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...18.1N 138.9E

ABOUT 450 MILES WEST OF AGRIHAN
ABOUT 495 MILES WEST-NORTHWEST OF SAIPAN
ABOUT 505 MILES NORTHWEST OF GUAM
ABOUT 910 MILES SOUTHEAST OF OKINAWA

MAXIMUM SUSTAINED WINDS...75 MPH
PRESENT MOVEMENT...WEST-NORTHWEST...300 DEGREES AT 16 MPH.

DISCUSSION AND OUTLOOK
----------------------
AT 100 AM CHST...1500 UTC...THE CENTER OF TYPHOON CHAN-HOM WAS
LOCATED BY SATELLITE NEAR LATITUDE 18.1 DEGREES NORTH AND LONGITUDE
138.9 DEGREES EAST. CHAN-HOM IS MOVING WEST-NORTHWESTWARD AT 16
MPH. THIS GENERAL MOTION WITH A SLIGHT DECREASE IN FORWARD SPEED IS
EXPECTED TO CONTINUE INTO WEDNESDAY MORNING.

MAXIMUM SUSTAINED WINDS HAVE INCREASED TO 75 MPH. TROPICAL STORM
FORCE WINDS EXTEND OUTWARD UP TO 105 MILES SOUTH OF THE CENTER...AND
UP TO 150 MILES NORTH OF THE CENTER. CHAN-HOM IS EXPECTED TO
CONTINUE INTENSIFYING OVER THE NEXT FEW DAYS.

NEXT ADVISORY
-------------
THE NEXT SCHEDULED ADVISORY WILL BE ISSUED BY THE NATIONAL WEATHER
SERVICE AT 800 AM LATER THIS MORNING.

$$

W. AYDLETT

[wxman57]

A recent ASCAT pass indicates that Chan-hom's wind field is at least twice as large as in the current JTWC advisory. I'm measuring TS winds out to 225nm northeast of the center. 50kt winds extend out to over 100nm NE and SE of the center. As the models had been projecting, Chan-hom is quite a large storm.

[Alyono]

no data indicate this is a typhoon. Inner core remains disorganized. In addition, the ASCAT is saying strong TS. Cannot rely upon Dvorak alone

[TheAustinMan]

no data indicate this is a typhoon. Inner core remains disorganized. In addition, the ASCAT is saying strong TS. Cannot rely upon Dvorak alone

Just wondering... how would you use ASCAT to ascertain the intensity of a storm of potentially typhoon strength? ASCAT rarely returns typhoon-force wind swaths and the last pass was at 12z.

[Yellow Evan]

no data indicate this is a typhoon. Inner core remains disorganized. In addition, the ASCAT is saying strong TS. Cannot rely upon Dvorak alone

I strongly but respectfully disagree. First of all,the inner core isn't that bad. All recent microwave passes indicate a mostly closed eyewall. Typical of low-end hurricane/typhoon intensity. Regarding ASCAT, ASCAT has a low bias due to low resolution and ASCAT isn't that useful when storms get above 50 knots, and honestly the fact it is showing 55-60 knot winds is a little surprising. Regarding Dvorak, it is data in the absence of recon, but if you wanna go that far, SAB is 4,0, but JTWC is 3.5 FT with a DT of 2.5 and a CI value of 4.0, which would support ~60 knots.

I'd go 70 knots. Look at how impressive the CDO is (even though it's mostly south of the center).

[wxman57]

I can't see any ASCAT winds over 50 kts. Latest microwave image was from 0930Z (link below). The center wasn't very organized then, but that was 8 hours ago. Given the low bias of ASCAT winds in heavier convection, I don't think we can rule out some 65kt winds NE and SE of the center. The main thing indicated by ASCAT is that Chan-hom's wind fields are much larger than the JTWC wind fields suggest, more than twice as large.

On the other hand, the JMA is the official agency for the West Pacific (not JTWC). JMA still has Chan-hom as a STS with 55kt 10-min winds.

http://www.nrlmry.navy.mil/tcdat/tc15/WPAC/09W.CHAN-HOM/tc_ssmis/91h/1degreeticks/20150706.0949.f18.x.91h_1deg.09WCHAN-HOM.60kts-978mb-172N-1407E.97pc.jpg

[Yellow Evan]

55 knt 10 min is 65 knt 1 min, right?

[Yellow Evan]

I can't see any ASCAT winds over 50 kts. Latest microwave image was from 0930Z (link below). The center wasn't very organized then, but that was 8 hours ago. Given the low bias of ASCAT winds in heavier convection, I don't think we can rule out some 65kt winds NE and SE of the center. The main thing indicated by ASCAT is that Chan-hom's wind fields are much larger than the JTWC wind fields suggest, more than twice as large.

On the other hand, the JMA is the official agency for the West Pacific (not JTWC). JMA still has Chan-hom as a STS with 55kt 10-min winds.

http://www.nrlmry.navy.mil/tcdat/tc15/W ... E.97pc.jpg

ASCAT isn't very good at depicting winds over 50-55 knts anyway, is it?

http://www.nrlmry.navy.mil/htdocs_dyn_p ... E.53pc.jpg

This is the latest microwave FYI Core not complete yet, but probs this is a typhoon.

[Alyono]

55 knt 10 min is 65 knt 1 min, right?

it's 62 kts. Just under typhoon intensity

[Yellow Evan]

55 knt 10 min is 65 knt 1 min, right?

it's 62 kts. Just under typhoon intensity

Which is also a T3.5 on their scale, which seems a bit low unless you're not using a CDO pattern.

[wxman57]

55 knt 10 min is 65 knt 1 min, right?

Here's an excellent paper on the conversion. I believe that the authors conclude that to convert "at-sea" winds from 10-min to 1-min you would multiply the 10-min wind by 1.05 and arrive at a 1-min wind of 57.8kts.

https://www.wmo.int/pages/prog/www/tcp/Meetings/HC31/documents/Doc.3.part2.pdf

[Yellow Evan]

55 knt 10 min is 65 knt 1 min, right?

Here's an excellent paper on the conversion. I believe that the authors conclude that to convert "at-sea" winds from 10-min to 1-min you would multiply the 10-min wind by 1.05 and arrive at a 1-min wind of 57.8kts.

https://www.wmo.int/pages/prog/www/tcp/ ... .part2.pdf

It's not an image

But thanks for the paper. Then again, is it worth converting the JMA estimates to 1-min? There estimates seems mostly based on their Koba table which when converted, doesn't line up with the Dvorak 1984's wind table well.

[Alyono]

55 knt 10 min is 65 knt 1 min, right?

it's 62 kts. Just under typhoon intensity

Which is also a T3.5 on their scale, which seems a bit low unless you're not using a CDO pattern.

I'm also getting a 3.5 for this. Not a true CDO

[wxman57]

It's not an image

But thanks for the paper. Then again, is it worth converting the JMA estimates to 1-min? There estimates seems mostly based on their Koba table which when converted, doesn't line up with the Dvorak 1984's wind table well.

Details, details ... (pdf not an image). As discussed in the paper, it's not an easy conversion to make, as a 10-min wind is an average between possibly significantly higher or lower winds. The question would be whether the period of higher winds lasts for a full minute or for long enough to make the 1-min winds higher than the 10-min winds. In all likelihood, Chan-hom was not a typhoon as of 15Z today. Recent satellite imagery (no microwave shots) does indicate continued strengthening since 15Z, so I suspect Chan-hom is very near typhoon intensity by now.

[Yellow Evan]

I'm also getting a 3.5 for this. Not a true CDO

Looking at it now, I might agree it is a T3.5. But I'd personally favor whatever the MET is (I'd say T4.0, since it looks better than it did 24 hours ago, so slow development trend) since PT is a borderline 4.0

So I'd give it a T4.0.

[cycloneye]

JMA upgrades to Typhoon.

TY 1509 (CHAN-HOM)
Issued at 18:50 UTC, 6 July 2015
<Analyses at 06/18 UTC>
Scale -
Intensity Strong
Center position N17°25'(17.4°)
E138°40'(138.7°)
Direction and speed of movement W 20km/h(10kt)
Central pressure 975hPa
Maximum wind speed near the center 35m/s(65kt)
Maximum wind gust speed 50m/s(95kt)
Area of 50kt winds or more ALL60km(30NM)
Area of 30kt winds or more ALL390km(210NM)

<Forecast for 07/18 UTC>
Intensity Very Strong
Center position of probability circle N19°00'(19.0°)
E134°20'(134.3°)
Direction and speed of movement WNW 20km/h(11kt)
Central pressure 950hPa
Maximum wind speed near the center 45m/s(85kt)
Maximum wind gust speed 60m/s(120kt)
Radius of probability circle 140km(75NM)
Storm warning area ALL280km(150NM)

<Forecast for 08/18 UTC>
Intensity Very Strong
Center position of probability circle N21°40'(21.7°)
E130°10'(130.2°)
Direction and speed of movement NW 20km/h(12kt)
Central pressure 925hPa
Maximum wind speed near the center 50m/s(100kt)
Maximum wind gust speed 70m/s(140kt)
Radius of probability circle 260km(140NM)
Storm warning area ALL480km(260NM)

<Forecast for 09/18 UTC>
Intensity Very Strong
Center position of probability circle N24°30'(24.5°)
E125°35'(125.6°)
Direction and speed of movement WNW 25km/h(13kt)
Central pressure 925hPa
Maximum wind speed near the center 50m/s(100kt)
Maximum wind gust speed 70m/s(140kt)
Radius of probability circle 390km(210NM)
Storm warning area ALL600km(325NM)

<Forecast for 10/18 UTC>
Center position of probability circle N26°55'(26.9°)
E120°50'(120.8°)
Direction and speed of movement WNW 20km/h(12kt)
Radius of probability circle 440km(240NM)

<Forecast for 11/18 UTC>
Center position of probability circle N28°10'(28.2°)
E117°50'(117.8°)
Direction and speed of movement WNW 15km/h(7kt)
Radius of probability circle 560km(300NM)

[Yellow Evan]

Likely means the JMA is giving this a 4.0.

[cycloneye]

WDPN31 PGTW 062100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W (CHAN-HOM) WARNING NR 26//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON (TY) 09W (CHAN-HOM), LOCATED APPROXIMATELY 770 NM
SOUTHEAST OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED WESTWARD AT 11
KNOTS OVER THE PAST SIX HOURS. ANIMATED IR IMAGERY SHOWS THE SYSTEM
HAS MAINTAINED CONVECTIVE SIGNATURE AND DEGREE OF WRAP INTO A DEFINED
LLCC. THE INITIAL POSITION IS BASED ON A LOW REFLECTIVITY CIRCULATION
FEATURE 061658Z NPP MICROWAVE PASS WITH HIGH CONFIDENCE. THE INITIAL
INTENSITY OF 65 KNOTS IS BASED ON THE DVORAK ESTIMATES FROM PGTW AND
RJTD. UPPER-LEVEL ANALYSIS INDICATES THAT TY 09W IS LOCATED IN A
FAVORABLE ENVIRONMENT WITH LOW VWS AND NEAR-RADIAL OUTFLOW, ENHANCED
BY A TUTT CELL TO THE NORTHEAST. TY 09W IS TRACKING ALONG THE
SOUTHERN PERIPHERY OF THE DEEP-LAYERED STR.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TY 09W IS FORECAST TO CONTINUE TRACKING WEST-NORTHWESTWARD
UNDER THE STEERING INFLUENCE OF THE STR ENTRENCHED TO THE NORTH.
DYNAMIC GUIDANCE IS IN TIGHT AGREEMENT THROUGH TAU 72 WITH A SPREAD
OF 90 NM IN SOLUTIONS AT TAU 72. ADDITIONALLY, ENSEMBLE GUIDANCE ALSO
INDICATES A HIGH PROBABILITY TRACK COINCIDENT WITH THE JTWC FORECAST
TRACK. TY 09W IS FORECAST TO INTENSIFY STEADILY THROUGH TAU 72 TO A
PEAK INTENSITY OF 130 KNOTS DUE TO FAVORABLE CONDITIONS.
C. AFTER TAU 72, TY CHAN-HOM WILL CONTINUE TO TRACK WEST-
NORTHWESTWARD TO NORTHWESTWARD UNDER THE INFLUENCE OF THE DOMINANT
STEERING STR. VWS AND UPPER-LEVEL DIVERGENCE WILL REMAIN FAVORABLE
THROUGH THE END OF THE FORECAST PERIOD; HOWEVER, COOLER SST AND LOWER
OHC VALUES, AS WELL AS LAND INTERACTION AFTER TAU 96, WILL SERVE TO
WEAKEN THE SYSTEM. DYNAMIC MODEL GUIDANCE DIVERGES AFTER TAU 72,
HOWEVER, THE BULK OF THE GUIDANCE IS IN GOOD AGREEMENT WITH A TRACK
NORTH OF TAIWAN. OVERALL, THERE IS HIGH CONFIDENCE IN THE JTWC
FORECAST TRACK.//
NNNN

[wxman57]

12Z EC is interesting - landfall in NE Taiwan then it moves SSW along the east coast of Taiwan for 12-18 hours then re-forms near NW Taiwan. Probably not...