Typhoon Chanchu

Here's a rather interesting development:

Typhoon Chanchu, in the South China Sea with 115-kt winds, is expected to turn N and strengthen over the next couple of days as it heads toward China.

The latest JTWC forecast is alarming: the 17 May 12Z fix has the center just SSW of Hong Kong and moving N with winds of 125 kt-- Cat 4 (USA). This track would expose the densely populated city to the severe right-semicircle. That would be quite interesting, to say the least.

Definitely something to watch over the next 72 hours.

Please note: These images will update dynamically and the commentary above will no longer apply as time passes.

wp0206.gif


rb-l.jpg
 
This is indeed very alarming and quite eerie given that this seems to be the exact scenario played out in Discovery Channel's "Perfect Disaster" series just a few weeks back. :blink: Same forecast strength, same direction of approach, same everything. If this really does play out like it probably will, it could be a very, very bad situation for Hong Kong, especially being in the right front semicircle. With the city being so densely populated, evacuating everyone would be impossible, and a lot of Hong Kong's poorest sections are close to or at sea level. It wouldn't be unreasonable to say that at least a few hundred, if not a thousand or more people could die if Chanchu makes a direct hit on Hong Kong :(
 
JTWC upgrades Chanchu to 130 knot winds, well ahead of intensification schedule, and peak intensity is now forecast at 145 knots! The storm is now forecast to make landfall at 135 knots which is the threshold of Category 5 intensity on the Saffir Simpson scale.

This could be a typhoon of unprecedented destruction not only in Hong Kong but possibly around the globe and it has its bullseye aligned on Hong Kong. I don't know what will happen to the numerous high rise buildings and the 6.9 million people that live there but it cannot be good. :(

Check out the NHC enhancement of this:
http://cimss.ssec.wisc.edu/tropic/real-tim...m/dvor-nh11.GIF
Wow, talk about a donuty core of real cold cloud tops.

This now has my full attention. Just posted on it in my blog.

Sad.
[/b]

Indeed this is incredible. I foresee global headline news in this respect over the next few days. Intensification imminent, cat 5+, HK a direct target. I am looking at a flight to HK as we speak. The Plains downtime has given me a window of opportunity.

Mark
 
I didn't want to blow the whistle too loudly and be an alarmist about this, but it does look like a truly remarkable situation setting up.

The recently updated JWTC forecast still takes the center on a worst-case track for Hong Kong-- just left of the city-- and the final center fix prior to landfall indicates 135 kt-- a top-end Cat 4 (USA). If this forecast verifies-- and the right-eyewall of a 135-kt typhoon passes directly over Hong Kong-- this will be one of the most destructive global meteorological events of the last 100 years.

A truly remarkable set of circumstances here...
 
I didn't want to blow the whistle too loudly and be an alarmist about this, but it does look like a truly remarkable situation setting up.

The recently updated JWTC forecast still takes the center on a worst-case track for Hong Kong-- just left of the city-- and the final center fix prior to landfall indicates 135 kt-- a top-end Cat 4 (USA). If this forecast verifies-- and the right-eyewall of a 135-kt typhoon passes directly over Hong Kong-- this will be one of the most destructive global meteorological events of the last 100 years.

A truly remarkable set of circumstances here...
[/b]

There is quite an abrupt turn to be made yet if HK comes in the firing line. It may smoothen somewhat and give HK some relief.

Mark
 
There is quite an abrupt turn to be made yet if HK comes in the firing line. It may smoothen somewhat and give HK some relief.

Mark
[/b]
Very true. As of the latest JTWC statement, it is still moving W at 6 kt. However, they seem to expect a sharp, hairpin turn to the N at any time. It's interesting to think that the precise timing of this turn could have global economic impact.

My business partner freaked out this evening when I informed him of the threat to Hong Kong-- he thinks a direct hit by such a severe storm could have global consequences. I'd tend to agree.

So... are you heading there to chase it?
 
1. SUPER TYPHOON 02W (CHANCHU) WARNING NR 025A CORRECTED
01 ACTIVE TROPICAL CYCLONE IN NORTHWESTPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
---
WARNING POSITION:
141800Z --- NEAR 13.8N 115.4E
MOVEMENT PAST SIX HOURS - 260 DEGREES AT 06 KTS
POSITION ACCURATE TO WITHIN 030 NM
POSITION BASED ON EYE FIXED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 130 KT, GUSTS 160 KT

Mark
 
Next warning update in a little over 3 hours. I think the discussion is updated then too. Guidance appears to be clustered around HK still...
[/b]
Hey Alex, thanks for posting the model guidance. It does appear to be pretty tightly clustered.

Are you referring to the next JTWC warning, or a different agency?
 
Hey Alex, thanks for posting the model guidance. It does appear to be pretty tightly clustered.

Are you referring to the next JTWC warning, or a different agency?
[/b]

JTWC warning, I believe it is updated at 0300Z and I think their forecast discussions are issued at 1500 and 0300Z. Correct me if I'm wrong, I'm new to their procedures...
 
JTWC warning, I believe it is updated at 0300Z and I think their forecast discussions are issued at 1500 and 0300Z. Correct me if I'm wrong, I'm new to their procedures...
[/b]
Me, too. ;) I'm not entirely clear on how it works.

I am of course solid on the Atlantic basin, and this year I educated myself on the Australian tropical-cyclone scene (including how the Australian BoM works)-- but the South China Sea is totally new turf for me and I am not entirely aware of what other English-language information resources there might be.

The issue with the JTWC is that they just don't update nearly as frequently as one would like for a big event like this.
 
Here's an early-morning visible shot (which will dynamically update). The system is impressive, though not entirely symmetric-- and the center is not totally distinct. Is that some dry air wrapping into the circulation? The JTWC puts it at 130 kt.

Please note: This image will update dynamically and the commentary above will no longer apply as time passes.
vis.jpg
 
Latest Intensity Forecasts:
temp1.png

I guess we will just ignore CHIPS like we had to do with SHIPS during most of 2005.

Make sure to check out the latest Morphed Microwave Imagery from CIMMS:
http://cimss.ssec.wisc.edu/tropic/real-tim...sBy12hr_07.html



The MIMIC (IR) also shows a nice intensification that was continuing as of 2230 UTC (even though the eye has become obsecured). The eye has tightend significantly from this morning and shows very cold cloud tops surronding it. Shear is very weak with just 5-10kts and the 18z Global GFS hasn't changed much and the trough trough in China still seems to be moving at the same speed bringing about a turn of the cyclone. The NCEP Cyclone track perturbed ensemble members seem clustered to the right of the GFS solution probably weakening the sub-trop ridge a little more than expected. The track consensus looks pretty good for this range though I wouldn't be suprised to see a shift with the amount of time still left. I did notice that the offical Hong Kong Tropical agency's track is east of most global members SEE HERE: http://www.hko.gov.hk/wxinfo/currwx/tc_0603.png. As of 2z the Dvorak IR is showing some warming in the eye though it's still pretty obsecured.



I'd be really concerned if this track holds true as NOGAPS wave forecasts are for 32ft max (this from a model which is not great with intensity.) Also the WAVE MODEL (WAM) is equally as grim forecasting 26-36ft sig wave heights. https://www.yoko.npmoc.navy.mil/yoko/ocean/...s_wam/scs05.gif
Thats pretty bad considering that the Hong Kong airport runway is 19ft above sea level! Thankfully it's slightly protected by being located north of an island. As for the intensity, shear is forecast to increase but doesn't become hostile. Sea tempatures do drop off a couple degrees centigrade as you go north but the depth to the 26C isotherm is still pretty deep.

From what i've read Hong Kong does seem to have taken some reasonable steps in construction/design and emergency preparedness for cyclones but a direct hit of a major cyclone could be quite a disaster.
 
Thanks, Scott, for that info. Interesting that the Hong Kong Observatory (HKO) recurves to the storm to the NE and spares Hong Kong a direct hit. I did some additional research this morning and also checked out the Japan Meteorological Agency (JMA), which I've been told is the "official" source for info Re: systems in this region.

As with tropical cyclones threatening Australia, the different agencies covering the South China Sea give conflicting views.

INTENSITY
As of the time of my writing this, the JTWC estimates 120 kt. The JMA indicates ~104 kt when their 10-min average value of 90 kt is converted to a 1-min value. That's a big difference. Both agencies now anticipate weakening as Chanchu moves N-- so the prognosis does not seem quite as dire as last night. Even so, the JTWC forecast still implies a direct hit on Hong Kong by a 105-kt typhoon (Cat 3 USA).

I notice in the latest satellite imagery (below) that the N portions of the system seem to eroding a bit.

TRACK
Again, opinions significantly diverge. The JTWC keeps Chanchu moving pretty-much due N, to Hong Kong, whereas the JMA (and HKO) indicate significant NE recurvature, sparing Hong Kong a direct hit.

OVERALL
From a standpoint of both intensity and track, the JTWC prediction is the most threatening to Hong Kong. I would be curious to know what causes the rather large differences between the JTWC's and JMA's opinions on this situation.

Please note: This image will update dynamically and the commentary above will no longer apply as time passes.
rb-l.jpg
 
I am reliably informed that the forecasters at the JTWC only have a couple of years tropical forecasting experience.

I'd go with JMA on the intensity.

Mark
 
All of a sudden the JTWC is calling for signifcant weakening as Chanchu approaches land, having it as a 85 knot storm hitting HK around 12Z on the 17th. Any explanations for why they are suddenly predicting this weakening trend and adjusting the landfall intensity so far downward? I'm confused, as the SST's and shear seem conducive to Chanchu remaining a Super Typhoon until landfall. Either something has changed drastically in the last 6 hours in regards to favorability for maintaining its present strength or intensifying or they're trying to prevent widespread panic in HK (which, if that is the case, which I hope it is not, is an incredibly bonehead maneuver on the part of the JTWC)
Any explanations on this dramatic change in forecast?
 
All of a sudden the JTWC is calling for signifcant weakening as Chanchu approaches land, having it as a 85 knot storm hitting HK around 12Z on the 17th. Any explanations for why they are suddenly predicting this weakening trend and adjusting the landfall intensity so far downward? I'm confused, as the SST's and shear seem conducive to Chanchu remaining a Super Typhoon until landfall. Either something has changed drastically in the last 6 hours in regards to favorability for maintaining its present strength or intensifying or they're trying to prevent widespread panic in HK (which, if that is the case, which I hope it is not, is an incredibly bonehead maneuver on the part of the JTWC)
Any explanations on this dramatic change in forecast?
[/b]

The JTWC is now calling storm intensity in line with JWA. Obviously the JTWC have been overplaying the call, which would explain my last comment with regards their forecasters inexperience. Stick with the JWA, which has been pretty consistent all along to date.
Mark
 
Very interesting development. In addition to the significant weakening now indicated (85 kt at landfall), the JTWC track is also curving more to the right-- and coming more in line with the JMA's. This puts Hong Kong on the weaker side of the system.

What a difference a day makes...

wp0206.gif
 
Yes what a 24 hrs :blink: There is also still plenty of moisture between now and landfall for it to change again. We watch with interest.

Mark
 
The threat to Hong Kong continues to diminish. The latest JTWC forecast is much more aligned with the JMA-- with both now indicating a moderate typhoon making landfall well E of Hong Kong. The JMA suggests ~80 kt around landfall (when their 10-min value of 70 kt is converted to a 1-min value using a standard 1.15 factor) whereas the JTWC-- always more bullish-- suggests 85 kt. Either way, there is consensus that Chanchu will be a borderline Cat 1/Cat 2 USA at landfall in China.

wp0206.gif
 
The JTWC and JMA are in relatively good agreement that Chanchu will come ashore or graze the China coast near the city of Shantou within the next 12 hours or so as an 80-kt (Cat 1 USA) typhoon.

I am certainly happy for Hong Kong. But of course that tiny (;)) side of me that sees hurricanes as a kind of grand natural theatre can only describe this ending as a slight anti-climax. :p

wp0206.gif
 
Back
Top