WPAC: CHAN-HOM - Post-Tropical

[xtyphooncyclonex]

the problem is, the mdoels initialized this now as a bonadife TC, when it is not

Nope, they show further weakening. Maybe to just less than STS-TS strength hitting Guam then later undergoing RI

If it's not a bonafide TC, then why is this a STS?

[xtyphooncyclonex]

Maybe about 55-65 kts, looks can be deceiving. Agree

[euro6208]

yeah looks can be deceiving...

don't forget the atlantic hurricanes we've seen the last few years

[xtyphooncyclonex]

And there are also impressive looking storms which are even weaker than this lol

[xtyphooncyclonex]

Saomai part 2??

[wxman57]

I don't think looks are too deceiving. Chan-hom is struggling. It doesn't appear to qualify for upgrade to a depression at this point. Disturbances east of it look stronger - more convection and LLCs, but they haven't been upgraded (particularly the one near 170E). ASCAT indicates some 35kt winds in that tiny area of squalls just south and east of the center.

In other news, latest GFS recurves it east of Japan while the 00Z Euro shifted westward to eastern China for eventual final landfall. 00Z GFS moved it into southern Japan.

[xtyphooncyclonex]

Now perhaps 40 kts. Center now well off the convection

[xtyphooncyclonex]

Downgraded

TS 1509 (CHAN-HOM)
Issued at 12:45 UTC, 3 July 2015

<Analyses at 03/12 UTC>
Scale -
Intensity -
Center position N11°00'(11.0°)
E148°30'(148.5°)
Direction and speed of movement Almost stationary
Central pressure 990hPa
Maximum sustained wind speed 23m/s(45kt)
Maximum wind gust speed 35m/s(65kt)
Area of 30kt winds or more ALL330km(180NM)

<Forecast for 04/12 UTC>
Intensity -
Center position of probability circle N12°55'(12.9°)
E147°20'(147.3°)
Direction and speed of movement NNW 10km/h(6kt)
Central pressure 980hPa
Maximum wind speed near the center 30m/s(55kt)
Maximum wind gust speed 40m/s(80kt)
Radius of probability circle 130km(70NM)
Storm warning area ALL200km(110NM)

<Forecast for 05/12 UTC>
Intensity Strong
Center position of probability circle N15°25'(15.4°)
E144°35'(144.6°)
Direction and speed of movement NW 15km/h(9kt)
Central pressure 965hPa
Maximum wind speed near the center 35m/s(70kt)
Maximum wind gust speed 50m/s(100kt)
Radius of probability circle 200km(110NM)
Storm warning area ALL310km(170NM)

<Forecast for 06/12 UTC>
Intensity Very Strong
Center position of probability circle N18°00'(18.0°)
E141°20'(141.3°)
Direction and speed of movement NW 20km/h(10kt)
Central pressure 950hPa
Maximum wind speed near the center 45m/s(85kt)
Maximum wind gust speed 60m/s(120kt)
Radius of probability circle 300km(160NM)
Storm warning area ALL440km(240NM)

[wxman57]

ASCAT indicates about 35 kts.

[xtyphooncyclonex]

In JMA standards this should be a TD already

[wxman57]

In JMA standards this should be a TD already

I agree that something like this wouldn't qualify for upgrade to a TS. Standards appear to be different for downgrading vs. upgrading (with all agencies). The thinking is that the general public can't comprehend that a storm may fluctuate in intensity or organization much, and they may take a system less seriously if it's downgraded.

[Alyono]

http://imageshack.com/a/img673/5686/1NSOF6.png

http://imageshack.com/a/img540/9924/jHVtyq.png

Just because its displaced on satpic don't mean its not a TC that would mean every system that has had a displaced llcc in its life time was not bonadife?



WP092015 CHAN-HOM for Run: 2015-07-03 06Z

you are aware that the multi-platform uses the JTWC as the first guess field, aren't you. Not reliable in this case

[wxman57]

I'm looking at a satellite loop and it appears that the center may be reforming to the north and merging with the disturbance immediately to its east.

[Yellow Evan]

In JMA standards this should be a TD already

I agree that something like this wouldn't qualify for upgrade to a TS. Standards appear to be different for downgrading vs. upgrading (with all agencies). The thinking is that the general public can't comprehend that a storm may fluctuate in intensity or organization much, and they may take a system less seriously if it's downgraded.

This would qualify as an upgraded to TS if there were TS winds.

[wxman57]

This would qualify as an upgraded to TS if there were TS winds.

Not necessarily. An upgrade requires more than just an area of TS winds. Many disturbances in the region have TS winds but aren't classified as tropical storms.

It's looking like a big mess on satellite now. There are two competing regions for the LLC.

[euro6208]

Wow...

What a weird looking TS...

Monsoon system?

[euro6208]

WDPN31 PGTW 031500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (CHAN-HOM) WARNING
NR 13//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 09W (CHAN-HOM), LOCATED APPROXIMATELY 277 NM
SOUTHEAST OF ANDERSEN AFB, GUAM HAS TRACKED NORTHEASTWARD AT 04
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY DEPICTS A BROAD AREA OF POORLY ORGANIZED CONVECTION SHEARED
WELL TO THE SOUTHWEST OF THE LOW LEVEL CIRCULATION CENTER (LLCC).
THE INITIAL POSIT IS EXTRAPOLATED FROM AN 031101Z ASCAT BULLSEYE
WITH GOOD CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED AT 45 KNOTS
BASED ON DVORAK CURRENT INTENSITY ESTIMATES FROM PGTW AND RJTD,
WHICH ARE SUPPORTED BY THE AFOREMENTIONED ASCAT PASS. TS 09W HAS
DISPLAYED DIRECT CYCLONE INTERACTION (DCI) WITH A REMANT CIRCULATION
TO THE NORTHEAST RESULTING IN A NORTHEASTERLY TRACK OVER THE PAST 12
HOURS. THE REMNANT LLCC, HOWEVER, HAS NO SURFACE REFLECTION IN TWO
RECENT SCATTEROMETRY PASSES, THEREFORE 09W REMAINS THE
DOMINANT CIRCULATION. AN AREA OF TROUGHING TO THE NORTH OF TS 09W IS
STILL IN PLACE PRODUCING INCREASED VERTICAL WIND SHEAR(VWS),
SUBSIDENCE AND INCREASED CONVERGENCE ALOFT. THESE IMPACTS ARE
SUPPRESSING CONVECTION.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TS 09W WILL CONTINUE TO DRIFT NORTH TO NORTHEASTWARD OVER THE
NEXT 12 HOURS WHILE TS 09W INTERACTS WITH THE REMNANT VORTEX IN A
WEAK STEERING ENVIRONMENT. AFTER THIS TIME, TS CHAN-HOM WILL TURN
BACK TO A NORTHWESTWARD TRACK AS THE TUTT CELL RETROGRADES TO THE
EAST AND THE REMNANT VORTEX DISSIPATES. THE SYSTEM SHOULD GRADUALLY
BEGIN TO REORGANIZE AS THE EFFECTS OF THE UPPER LEVEL TROUGHING
SUBSIDES, RESULTING IN LOWER VWS AND IMPROVING OUTFLOW. THIS
INTENSIFICATION WILL CONTINUE THROUGHOUT THE REMAINDER OF THIS
FORECAST PERIOD. DYNAMICAL MODELS ARE NOT HANDLING THIS COMPLEX
CYCLONE INTERACTION AND TUTT CELL IMPACTS. THE OFFICIAL FORECAST IS
SLOWER THAN CONSENSUS, WITH POOR CONFIDENCE.
C. IN THE EXTENDED TAUS, TS CHAN-HOM WILL CONTINUE TO TRACK
NORTHWESTWARD AND FURTHER INTENSIFY AS VWS AND OUTFLOW REMAIN
FAVORABLE. DYNAMIC MODEL GUIDANCE DIVERGES GREATLY AROUND TAU 96
ASSOCIATED WITH THE TIMING OF EVENTUAL RECURVATURE. THEREFORE, THERE
IS LOW CONFIDENCE IN THIS PORTION OF THE FORECAST.//
NNNN

[Yellow Evan]

This would qualify as an upgraded to TS if there were TS winds.

Not necessarily. An upgrade requires more than just an area of TS winds. Many disturbances in the region have TS winds but aren't classified as tropical storms.

It's looking like a big mess on satellite now. There are two competing regions for the LLC.

Would an increase in intensity from 35 to 40 knt require more than just an area of TS winds.

If not, why is that a requirement if you're only gonna enforce it with 35 knt systems?

[euro6208]

Alot of uncertainty but we would welcome the cool rainy weather that looks to stay

CHAN-HOM REMAINS A TROPICAL STORM THIS MORNING. AGAIN THE TRACK
IS THE BIG QUESTION. THE EARLIER TRACK HAD CHAN-HOM PASSING CLOSE
TO GUAM. LAST NIGHTS TRACK PREDICTION SHOWED THE TROPICAL STORM
PASSING THROUGH THE TINIAN CHANNEL. THE LATEST TRACK FORECAST
SHOWS CHAN-HOM PASSING NORTH OF SAIPAN.

THIS MORNINGS FORECAST REFLECT THE CHANGE WITH GUAM AND ROTA PROBABLY
ONLY GETTING TROPICAL STORM FORCE WINDS BRIEFLY AT BEST. TINIAN
AND SAIPAN MAY BRIEFLY SEE TYPHOON FORCE WINDS SUNDAY NIGHT. GUAM
AND ROTA ARE STILL UNDER A TYPHOON WATCH THIS MORNING. AS IS
APPARENT FROM WATCHING THIS SYSTEM OVER THE LAST FEW DAYS IS THAT
THE TRACK FORECAST HAS CHANGED OFTEN. WILL LEAVE GUAM AND ROTA IN
THE WATCH UNTIL THE FORECAST TRACK IS BETTER BEHAVED.

THE INTENSITY FORECAST IS NOT SO CERTAIN EITHER AS CHAN-HOM IS
VERY DISORGANIZED THIS MORNING. WILL IT REGAIN TYPHOON INTENSITY
AS PREDICTED IS A BIG QUESTION. AGAIN BECAUSE OF THE BIG
UNCERTAINTY TYPHOON CONDITIONS ARE POSSIBLE AT SOME POINT THROUGH
SUNDAY NIGHT.

AFTER CHAN-HOMS PASSAGE THE MARIANAS WILL BE IN SOUTHWEST WINDS
AS THE STORM WILL DRAG THE MONSOON TROUGH NORTH OF THE LOCAL AREA.

[wxman57]

Would an increase in intensity from 35 to 40 knt require more than just an area of TS winds.

If not, why is that a requirement if you're only gonna enforce it with 35 knt systems?

It needs a well-defined low-level circulation center with organized convection. Wind alone won't cut it.