WPAC: GUCHOL - Post-Tropical

[RobWESTPACWX]

JMA has been very conservative this season with all the storms. It seems they have a new forecaster there or a new way of doing things. But ya, it seems consistently low. Basically there STS is the equivalent as a JTWC TY at this point. I think thats how it should be looked as.

[francis327]

From what I observe from the JMA data that I have collected since the start of the storm season from Tropical Depression 01W (JTWC) until current Severe Tropical Storm Guchol, I realize that the trend of JMA in classifying whether the storm is a TS, STS, and TY is based on Pressure.

In order for a Storm to get into TY status from JMA, the pressure should go far below than 975, i.e
1203 Mawar gets as low as 970 and classified as Typhoon
1202 Sanvu gets as low as 975 and classified as Severe Tropical Storm (same as Guchol now)
1201 Pakhar gets only to 998 so it remains as Tropical Storm

I would summarize thing as follow:
From a Tropical Depression to a Tropical Storm, it will still depends on the Wind intensity.
below 990 - Severe Tropical Storm
below 975 - Typhoon

The data I have collected from JMA over the 5 storms is at below.
http://www.westernpacificweather.com/we ... al/2012-2/

click on the name of each storm to proceed to data page.

Thanks

[RobWESTPACWX]

Model outlook is still very tight, sadly for Okinawa's case though.

[cycloneye]

JTWC initial intensity on this 15:00z warning is 90kts and now has peak intensity at 115 kts. Infdidoll, is at 100 kts when it moves just east of Okinawa.

WTPN31 PGTW 151500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE WARNING//
RMKS/
1. TYPHOON 05W (GUCHOL) WARNING NR 019
01 ACTIVE TROPICAL CYCLONE IN NORTHWESTPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
151200Z --- NEAR 11.2N 130.9E
MOVEMENT PAST SIX HOURS - 325 DEGREES AT 07 KTS
POSITION ACCURATE TO WITHIN 020 NM
POSITION BASED ON EYE FIXED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 090 KT, GUSTS 110 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 064 KT WINDS - 035 NM NORTHEAST QUADRANT
035 NM SOUTHEAST QUADRANT
035 NM SOUTHWEST QUADRANT
035 NM NORTHWEST QUADRANT
RADIUS OF 050 KT WINDS - 055 NM NORTHEAST QUADRANT
055 NM SOUTHEAST QUADRANT
055 NM SOUTHWEST QUADRANT
055 NM NORTHWEST QUADRANT
RADIUS OF 034 KT WINDS - 085 NM NORTHEAST QUADRANT
080 NM SOUTHEAST QUADRANT
080 NM SOUTHWEST QUADRANT
085 NM NORTHWEST QUADRANT
REPEAT POSIT: 11.2N 130.9E
---
FORECASTS:
12 HRS, VALID AT:
160000Z --- 12.6N 129.8E
MAX SUSTAINED WINDS - 095 KT, GUSTS 115 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 064 KT WINDS - 035 NM NORTHEAST QUADRANT
035 NM SOUTHEAST QUADRANT
035 NM SOUTHWEST QUADRANT
035 NM NORTHWEST QUADRANT
RADIUS OF 050 KT WINDS - 060 NM NORTHEAST QUADRANT
060 NM SOUTHEAST QUADRANT
055 NM SOUTHWEST QUADRANT
060 NM NORTHWEST QUADRANT
RADIUS OF 034 KT WINDS - 095 NM NORTHEAST QUADRANT
090 NM SOUTHEAST QUADRANT
090 NM SOUTHWEST QUADRANT
095 NM NORTHWEST QUADRANT
VECTOR TO 24 HR POSIT: 330 DEG/ 11 KTS
---
24 HRS, VALID AT:
161200Z --- 14.5N 128.7E
MAX SUSTAINED WINDS - 105 KT, GUSTS 130 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 064 KT WINDS - 040 NM NORTHEAST QUADRANT
040 NM SOUTHEAST QUADRANT
040 NM SOUTHWEST QUADRANT
040 NM NORTHWEST QUADRANT
RADIUS OF 050 KT WINDS - 065 NM NORTHEAST QUADRANT
065 NM SOUTHEAST QUADRANT
060 NM SOUTHWEST QUADRANT
065 NM NORTHWEST QUADRANT
RADIUS OF 034 KT WINDS - 110 NM NORTHEAST QUADRANT
105 NM SOUTHEAST QUADRANT
100 NM SOUTHWEST QUADRANT
105 NM NORTHWEST QUADRANT
VECTOR TO 36 HR POSIT: 340 DEG/ 13 KTS
---
36 HRS, VALID AT:
170000Z --- 16.9N 127.8E
MAX SUSTAINED WINDS - 115 KT, GUSTS 140 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 064 KT WINDS - 045 NM NORTHEAST QUADRANT
040 NM SOUTHEAST QUADRANT
040 NM SOUTHWEST QUADRANT
040 NM NORTHWEST QUADRANT
RADIUS OF 050 KT WINDS - 070 NM NORTHEAST QUADRANT
065 NM SOUTHEAST QUADRANT
065 NM SOUTHWEST QUADRANT
065 NM NORTHWEST QUADRANT
RADIUS OF 034 KT WINDS - 120 NM NORTHEAST QUADRANT
115 NM SOUTHEAST QUADRANT
110 NM SOUTHWEST QUADRANT
115 NM NORTHWEST QUADRANT
VECTOR TO 48 HR POSIT: 350 DEG/ 14 KTS
---
EXTENDED OUTLOOK:
48 HRS, VALID AT:
171200Z --- 19.6N 127.3E
MAX SUSTAINED WINDS - 115 KT, GUSTS 140 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 064 KT WINDS - 045 NM NORTHEAST QUADRANT
045 NM SOUTHEAST QUADRANT
040 NM SOUTHWEST QUADRANT
040 NM NORTHWEST QUADRANT
RADIUS OF 050 KT WINDS - 070 NM NORTHEAST QUADRANT
070 NM SOUTHEAST QUADRANT
065 NM SOUTHWEST QUADRANT
070 NM NORTHWEST QUADRANT
RADIUS OF 034 KT WINDS - 125 NM NORTHEAST QUADRANT
125 NM SOUTHEAST QUADRANT
120 NM SOUTHWEST QUADRANT
120 NM NORTHWEST QUADRANT
VECTOR TO 72 HR POSIT: 010 DEG/ 14 KTS
---
72 HRS, VALID AT:
181200Z --- 25.2N 128.2E
MAX SUSTAINED WINDS - 100 KT, GUSTS 125 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 064 KT WINDS - 040 NM NORTHEAST QUADRANT
040 NM SOUTHEAST QUADRANT
040 NM SOUTHWEST QUADRANT
040 NM NORTHWEST QUADRANT
RADIUS OF 050 KT WINDS - 070 NM NORTHEAST QUADRANT
070 NM SOUTHEAST QUADRANT
065 NM SOUTHWEST QUADRANT
065 NM NORTHWEST QUADRANT
RADIUS OF 034 KT WINDS - 135 NM NORTHEAST QUADRANT
135 NM SOUTHEAST QUADRANT
130 NM SOUTHWEST QUADRANT
130 NM NORTHWEST QUADRANT
VECTOR TO 96 HR POSIT: 035 DEG/ 23 KTS
---
LONG RANGE OUTLOOK:
---
96 HRS, VALID AT:
191200Z --- 32.3N 134.7E
MAX SUSTAINED WINDS - 070 KT, GUSTS 085 KT
WIND RADII VALID OVER OPEN WATER ONLY
BECOMING EXTRATROPICAL
VECTOR TO 120 HR POSIT: 045 DEG/ 25 KTS
---
120 HRS, VALID AT:
201200Z --- 38.7N 143.9E
MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
WIND RADII VALID OVER OPEN WATER ONLY
EXTRATROPICAL
---
REMARKS:
151500Z POSITION NEAR 11.6N 130.6E.
TYPHOON (TY) 05W (GUCHOL), LOCATED APPROXIMATELY 660 NM EAST-
SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWESTWARD
AT 07 KNOTS OVER THE PAST SIX HOURS. MAXIMUM SIGNIFICANT
WAVE HEIGHT AT 151200Z IS 33 FEET. NEXT WARNINGS AT
152100Z, 160300Z, 160900Z AND 161500Z.//
NNNN

[RobWESTPACWX]

JTWC is looking to the right of okinawa now, interesting, and good news.

[Chacor]

From what I observe from the JMA data that I have collected since the start of the storm season from Tropical Depression 01W (JTWC) until current Severe Tropical Storm Guchol, I realize that the trend of JMA in classifying whether the storm is a TS, STS, and TY is based on Pressure.

In order for a Storm to get into TY status from JMA, the pressure should go far below than 975, i.e
1203 Mawar gets as low as 970 and classified as Typhoon
1202 Sanvu gets as low as 975 and classified as Severe Tropical Storm (same as Guchol now)
1201 Pakhar gets only to 998 so it remains as Tropical Storm

I would summarize thing as follow:
From a Tropical Depression to a Tropical Storm, it will still depends on the Wind intensity.
below 990 - Severe Tropical Storm
below 975 - Typhoon

The data I have collected from JMA over the 5 storms is at below.
http://www.westernpacificweather.com/we ... al/2012-2/

click on the name of each storm to proceed to data page.

Thanks

Wow… that's nonsense. I know that's a strong word, but there's no other suitable word to use to describe that.

A typhoon is 64 knots and above. Pressure is not taken into account when upgrading systems.

[RobWESTPACWX]

Well to be fair, when forecasting storms in the western pacific where no recon is available pressure is a mirror reflection of winds, all the agencies do exactly that, even though JTWC does not release pressure in there forecast the still go through the DVORAK system to get it.

In this case with JMA they have set 975 to be there limit for a typhoon or not apparently. Its all a estimation though since there is no one out there with a barometer. But it may explain why they hold off on upgrading it to a typhoon.

[Chacor]

It may very well be the case that pressure–wind relationships are employed in the WPac by the JMA. But it is still silly to draw a conclusion that a typhoon upgrade is based on pressure, rather than by wind. Especially since the accepted understanding WORLDWIDE is that TC status is based on winds.

[RobWESTPACWX]

I think the typhoon is upgraded by winds in JMA's case, but they have shown the pattern of using the pressure as thumb rule apparently. When Im in talking to some of the Japanese Mets on Monday I'll ask them what they think, the above are just observations over a period of time and with the information gathered a pattern has been occurring. Lets remember this and see if it holds true when this storm goes to TY and for future storms.

[RobWESTPACWX]

Next update comes out in 30min, if the pressure drops then we will find out of the theory holds true.

[Chacor]

Four storms is a very small sample size…

[Chacor]

WTPQ20 RJTD 151500
RSMC TROPICAL CYCLONE ADVISORY
NAME STS 1204 GUCHOL (1204)
ANALYSIS
PSTN 151500UTC 11.3N 130.6E FAIR
MOVE NNW 06KT
PRES 975HPA
MXWD 060KT
GUST 085KT
50KT 50NM
30KT 140NM
FORECAST
24HF 161500UTC 13.8N 128.7E 75NM 70%
MOVE NNW 14KT
PRES 960HPA
MXWD 075KT
GUST 105KT
45HF 171200UTC 17.6N 126.8E 140NM 70%
MOVE NNW 11KT
PRES 945HPA
MXWD 080KT
GUST 115KT
69HF 181200UTC 21.6N 126.5E 220NM 70%
MOVE N 10KT
PRES 940HPA
MXWD 085KT
GUST 120KT =

[RobWESTPACWX]

Just observations Chacor, the pattern holds true back farther as well. A true scientific process to try to determine the reasoning behind holding off on upgrading the storm.

Still no confirmation yet on it. Pressure remains 975hpa according to JMA at 15UTC.

http://www.jma.go.jp/en/typh/12045c.html

I can say that JTWC does the same exact thing though, they use the DVORAK system and then match it up with winds that should be seen at that pressure. They just don't release pressure so we can't verify it.

The lower the pressure the tighter the pressure gradient the faster the wind speed right? So wouldn't a lower pressure mean faster winds?

Good healthy discussion regardless, Im learning some stuff here I hope we all are.

[RobWESTPACWX]

I don't like using wikipedia, but this is a good place to see what I'm talking about, DVORAK intensity for a Cat 1 Typhoon is at 976HPA, very close to 975hpa. As well. So it would stand to reason JMA just goes a little lower with there pressure for a TY. And uses DVORAK to to estimate its intensity based on pressure to get the winds. This is a sound and true method. And what most tropical forecasters use when no recon or surface data is available.

http://en.wikipedia.org/wiki/Dvorak_technique

Now I think what the bigger issue is and what we may disagree with is if the pressure is deeper than 975hpa at this time.

[Chacor]

The JMA have their own Dvorak scale, and don't follow the US one, for the record.

[francis327]

http://www.wmo.int/pages/prog/www/tcp/d ... alysis.pdf





To be at T4.0 for JMA hPA is 973 and Wind at 64kt if the above table still applicable.

[RobWESTPACWX]

Ok, thanks Francis for posting that, I should have known better not to refer to the American one, I just wanted to point out that pressure is a direct influence on winds. So one would assume the lower pressure would be used as a thumb rule to upgrade the storm to a typhoon as we return to the original statement that it would be nonsense to think that it is. Thats all..

Once again great discussion, not trying to get personal. I hope were all on the same page.

[RobWESTPACWX]

Back to the storm though, model consensus every so slightly shift to the right, Okinawa still in the line of fire though.

[RobWESTPACWX]

I would go back to thinking the pressure is lower though, impossible to see in IR but Microwave imagery shows a distinct eye after we look through the high clouds.

[euro6208]

WDPN31 PGTW 151500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 05W (GUCHOL) WARNING NR 19//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON (TY) 05W (GUCHOL), LOCATED APPROXIMATELY 660 NM EAST-
SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWESTWARD AT 07
KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED (IR) SATELLITE
IMAGERY DEPICTS A SMALL, COMPACT SYSTEM WITH A 110 NM DIAMETER
CENTRAL DENSE OVERCAST WITH A BANDING FEATURE OVER THE SOUTHEAST
QUADRANT AND A DEVELOPING CLOUD-FILLED EYE (-74C). A 151148Z SSMIS
IMAGE SHOWS A STRONG MICROWAVE EYE FEATURE, WHICH IS COINCIDENT WITH
THE WARM SPOT OBSERVED IN IR IMAGERY. BASED ON THIS RECENT
CONSOLIDATION, THERE IS GOOD CONFIDENCE IN THE CURRENT POSITION AND
RECENT TRACK MOTION TOWARD THE NORTHWEST. THE CURRENT INTENSITY IS
BASED ON DVORAK ESTIMATES OF 90 KNOTS FROM KNES AND PGTW. UPPER-
LEVEL ANALYSIS INDICATES IMPROVED OUTFLOW WITH POLEWARD OUTFLOW
ENHANCED BY A BROAD TUTT CELL CENTERED TO THE NORTHEAST (17N 140E).
THERE IS GOOD EVIDENCE THAT TY 05W IS FINALLY TURNING POLEWARD ALONG
THE SOUTHWEST PERIPHERY OF THE SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TY 05W IS EXPECTED TO CONTINUE TRACKING POLEWARD ALONG THE
WESTERN PERIPHERY OF THE STR. UPPER-AIR DATA INDICATES THAT THE
WESTERN STR REMAINS WEAK WITH RIDGING EXTENDING INTO THE SOUTH CHINA
SEA, AND THAT WESTERLY FLOW IS DOMINATING EAST CHINA AND THE EAST
CHINA SEA. MODEL GUIDANCE IS IN VERY TIGHT AGREEMENT THROUGH TAU 72,
THEREFORE, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST THROUGH TAU
72. TY 05W IS EXPECTED TO INTENSIFY THROUGH THE FORECAST PERIOD
UNDER FAVORABLE, IMPROVING CONDITIONS. BASED ON THE RECENT
CONSOLIDATION AND IMPROVED OUTFLOW, THE PEAK INTENSITY HAS BEEN
INCREASED TO 115 KNOTS.
C. IN THE EXTENDED TAUS, TY 05W IS FORECAST TO TRACK NEAR OKINAWA
THEN RE-CURVE NORTHEASTWARD TOWARD WESTERN JAPAN. DYNAMIC MODEL
GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 96 BUT DIVERGES DUE TO
COMPLEX, ERRONEOUS INTERACTIONS WITH THE MIDLATITUDE FLOW. THE
MAJORITY OF MODEL GUIDANCE IS PUNCHING THE SYSTEM INTO THE WESTERLY
JET, WHICH IS A FAIRLY TYPICAL PROBLEM BUT ENTIRELY UNREALISTIC.
THEREFORE, THE JTWC FORECAST IS POSITIONED TO THE RIGHT OF THE MODEL
CONSENSUS AND INDICATES A MORE EASTWARD TRAJECTORY TOWARD CENTRAL
JAPAN. THE 15/00Z ECMWF MODEL RUN DEPICTS A MORE REALISTIC TURN
EASTWARD DUE TO STRONG WESTERLY MIDLATITUDE FLOW AND SUPPORTS THE
JTWC FORECAST. TY 05W IS ALSO EXPECTED TO ENCOUNTER STRONG VERTICAL
WIND SHEAR (VWS) AND COOLER SST JUST NORTH OF OKINAWA AND SHOULD
ACCELERATE AS IT BEGINS EXTRA-TROPICAL TRANSITION (ETT). TY 05W
SHOULD COMPLETE ETT NEAR TAU 120 AS IT BECOMES EMBEDDED IN THE
BAROCLINIC ZONE OVER CENTRAL JAPAN. THE SYSTEM WILL WEAKEN RAPIDLY
DUE TO THE VWS AND INTERACTION WITH LAND BUT SHOULD MAINTAIN GALE-
FORCE WINDS AS AN EXTRA-TROPICAL LOW AFTER TAU 120. THERE IS LOW
CONFIDENCE IN THIS EXTENDED FORECAST DUE TO UNCERTAINTIES IN
ORIENTATION AND STRENGTH OF THE MIDLATITUDE SHORTWAVE TROUGH
EXPECTED TO DIG INTO THE EAST CHINA SEA NEAR TAU 72. ADDITIONALLY,
AS MENTIONED EARLIER, MODEL GUIDANCE IS IN POOR AGREEMENT AFTER TAU
96.//
NNNN



looks like carlotta is rapidly intensifying and guchol is next in line!