Unpacking the Yasi hype

* Below is a guest post written by Ken G, a long-time Darwin resident and media/IT professional.  Ken discussed his ideas not only with Darwin “storm chaser” enthusiasts but with Darwin residents who went through Cyclone Tracy.  It’s a keen amateur perspective on a frightening weather event but well worth reading in my opinion.

Cyclone Yasi was a big and scarey storm system.  Media and politicians continue to refer to it as a Category 5 cyclone with winds nearing 300 kmh near its centre, the largest cyclone ever to hit a populated area in Australia.  But is that really true?  A fairly obscure story on Australian Geographic website points out that “the full force may never be known because there are no gauges where the monster storm made landfall” and an engineer interviewed on last Friday’s 7:30 Report suggested that available data indicated Yasi was probably a small to medium Category 4 system with winds a bit over 200 kmh.  But that’s just about the full extent of any questioning of Yasi’s actual strength and destructive force.  What does the evidence actually tell us?

Don’t get me wrong; it did seem like it was going to be a very large event and government authorities were well justified in taking the steps they did to encourage residents to take it very seriously.  Looking at the Bureau of Meteorology site and at the radar images you could see this was a very nasty storm that was going to hit the coast.  Moreover, even if it WAS “only” a small-medium Category 4 cyclone that’s still a very large storm with frightening and lethal destructive force.

A number of observations sites did register very high wind readings (Lucinda Point 185km/h) and some stopped working after the main part of the storm hit them.  What we are unable to see from these observations is the estimated wind speed of 290 to 300 kilometres per hour.  How is the Bureau of Meteorology estimating these wind speeds?  If you look at the observations for Finders Reef, less than 90km south of the cyclone at 11.30 pm the night of the cyclone we see wind gusts to 109km/h but the Bureau of Meteorology and the US navy weather site was showing a estimated wind speed of 125knt or about 230km/h for the similar location.  If these higher wind speeds are correct then why are the ground stations getting the wind speed so wrong? Should we be relying on these ground stations for information?

“US Navy Weather site”: http://www.nrlmry.navy.mil/tc_pages/tc_home.html

“Flinders Reef” Bureau of Meteorology Observations

“Lucinda Point” Bureau of Meteorology Observations

Maximum Recorded wind speed 185km/h at Lucinda Point

However, we need to be a little careful here.  Lucinda Point is around 80 kilometres as the crow flies from Mission Beach where apparently the centre of Yasi’s eye made landfall, and maximum wind speeds tend to drop off quite rapidly as one moves away from the centre of a cyclone.  In a typical cyclone maximum wind speeds are experienced within about 20 kilometres of the edge of the eye.  Yasi’s eye was apparently about 80 kilometres in diameter and so we would expect Lucinda to be just outside the area where maximum wind speeds were experienced.  Thus this reading does suggest that Yasi was a Category 4 system, and quite possibly a significant one with destructive wind gusts well into the 200 km/h plus zone.

The physical evidence of destruction in the path of this cyclone is also interesting as most of the damage does not appear to support the 300 km/h estimated wind speeds quoted by the Bureau of Meteorology and media.
If you look at images of the destruction of Darwin after cyclone Tracy (a large category 4 cyclone as stated by the Bureau of Meteorology) you will see not only 80% of all buildings destroyed but the total lack of vegetation left in its path.  You might explain the discrepancy between Tracy and Yasi in terms of destruction of the built environment by the fact that Building Codes are so much more rigorous today than they were in 1974, but it seems highly unlikely that they’re growing trees more cyclone-hardy than they were 36 years ago. This is not just trees stripped of their leaves but the trees no longer there and the almost total destruction of all utilities for a city of 40,000 people at that time.

(Tropical Cyclone Tracy is arguably the most significant tropical cyclone in Australia’s history to hit a significant populated area.  It accounted for 65 lives, the destruction of most of Darwin and profoundly affected the Australian perspective to the tropical cyclone threat.

The media has played this current cyclone up so much that is almost impossible to get a true picture of what has happened. The media statements like “the destruction was like an atomic bomb” is so incorrect, go to Hiroshima and have a look at the museum and look at the images, Cyclone Yasi was nothing like an atomic bomb. Go to the Darwin museum and have a look at the Tracy exhibition, look at the videos of people and the destruction after Cyclone Tracy and see the total despair that cyclone brought to Darwin.

If we are to believe the media hype Cyclone Yasi was and is a category 5 severe storm that has wreaked havoc from as far north as Port Douglas and south to Mackay when in fact Dunk Island through to Tully experienced the full force of this cyclone and came out with building, trees and water damage on a scale far less than that of Tracy, and certainly not the enormous loss of life that the media was predicting only the night before.
To leave the impression that much of North Queensland’s coast experienced a category 5 cyclone is incorrect and belittles the people of Dunk Island, Mission Beach and the Tully region that lived through this storm.
I feel for the people that have gone through this event and fear for their safety should an actual category 5 cyclone hit.  After reading an article on the web from someone that was in Tully the night of the cyclone and his statement of 300km/h winds I have to wonder, I am sure it felt like 300km/h winds to him but is this scientific data that can be relied on?

As someone that lives in Tropical Australia and every year face the cyclone season it would be good to have true and accurate information from the Bureau of Meteorology and not the hype of the media to make informed decisions about your own safety. It would be good to find out exactly how the Bureau of Meteorology predicts the wind speed for these events and what place the ground observation stations play in this. Can we rely on the Bureau of Meteorology for true and accurate forecasting of these extreme weather conditions or are they simply too underfunded to do this job with any accuracy and allow the media to take control?   As someone has said the Bureau of Meteorology is usually 100% correct for yesterday’s weather so will they now correct history and tell Australia what the actual wind speed and the true category rating of Cyclone Yasi?

Why is that important?  The engineer interviewed on last Friday’s 7:30 Report explained it quite well.  Houses in both North Queensland and the Northern Territory are required to be engineered to withstand category 4 cyclones.  But there’s a huge difference between 200 km/h winds (the strongest gusts in a smallish Category 4 cyclone) and 300 km/h winds.  Winds around 300 km/h actually exert forces on buildings that are twice as strong as at 200 km/h, so that a house engineered to withstand the former may well not survive the latter.  If people living around Innisfail, Tully and Mission Beach are left with an erroneous understanding that their houses withstood a Category 5 cyclone (as most did), it may well be much more difficult next time a large cyclone threatens to persuade them to evacuate their homes and save their lives.  Media hyperbole may end up being a contemporary version of the boy who cried wolf once too often.

About Ken Parish

Ken Parish is a legal academic, with research areas in public law (constitutional and administrative law), civil procedure and teaching & learning theory and practice. He has been a legal academic for almost 20 years. Before that he ran a legal practice in Darwin for 15 years and was a Member of the NT Legislative Assembly for almost 4 years in the early 1990s.
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11 years ago

“If you look at the observations for Finders Reef, less than 90km south of the cyclone at 11.30 pm the night of the cyclone we see wind gusts to 109km/h but the Bureau of Meteorology and the US navy weather site was showing a estimated wind speed of 125knt or about 230km/h for the similar location.”

Are you sure this is correct as Flinders Reef on the BOM radar appears some 230km east of Mission Beach, which would make it approximately 200km east of the cyclone eye at 11.30pm? The NE wind direction at Flinders would also correlate with this, although I’m confused as to why the wind at Lucinda should be NW at a time when it was 80km almost directly south of the eye?

I’m a Cairns resident who was safely absent in NSW observing the cyclones progress towards my home, which was evacuated. The cyclone eye appeared to be clearly visible on the radar and passed between Flinders and Holmes Reefs much earlier in the day. The eye appeared on the rain radar as about 50km diameter as it approached the coast although that may be not a scientifically valid measurement technique! The leading edge of the eye appeared to hit the coast at Bingil Bay within minutes of midnight.

Always best to be on the north side of a cyclone, on the east coast at least, which is why Cairns has been lucky with both Yasi and Larry. Thanks for an interesting post.

11 years ago

There’s certainly a story in this about the media being less helpful and more sensationalist than desirable, but this is a pretty poor article.

Kenny G hasn’t given any thought to whether instruments can be reliable at wind speeds greater than 200km/h (and if they’re going to be robust enough to deal with those speeds, you’d think their accuracy at low speeds is going to be limited), discounting the possibility that their may not be accurate records available. The BoM doppler radar was giving the Cat 5 cyclone speeds, but when that site (Willis Island) fell over as the cyclone passed no anemometer data were available.

Kenny also seems pretty happy to discount the physical evidence and hasn’t compared different vegetation types Darwin/Tully Heads, different housing densities, nor compared damage for pre/post 1975 construction in the same place.

By all media accounts, damage for TC Yasi has been much greater than for TC Larry, and both cyclones impacted very similar regions relatively close together. TC Larry was a Cat 4 event, where does that leave the categorisation for Yasi?

11 years ago

Most of the time, cyclone intensity is estimated from satellite data – after all, most of the time they are over the ocean. This uses empirical relationships between satellite cloud properties, central pressure and winds in the eyewall, which are mostly derived from aircraft data in the North Atlantic (where they routinely fly Air Force planes into hurricanes to drop instruments) and Northwest Pacific, plus the fairly small number of cyclones where there are reliable surface data from the centre for both pressure and wind speed.

For Yasi, there are no reliable wind speed measurements for the eyewall – places like Lucinda Point and Flinders Reef are too far away – but there are two pressure measurements from the Tully area of 929 and 930 hectopascals (one from a Queensland government site, one from a private observer), which are entirely consistent with something around the category 4/category 5 boundary.

Jacques Chester
Jacques Chester
11 years ago

When STC Monica struck Arnhem land, it left a trail of visible deforestation. I’m relieved that Yasi turned out not to be as destructive as feared — but like Ken I look at the aftermath and wonder at the lack of arboreal destruction.

11 years ago

Cyclone wind speeds are estimated using the Dvorak technique from satellite imagery. NOAA estimated the highest wind speed at 127 kt and the UW-CIMSS put it at between 125 and 140kt depending on the model parameters. All of these are high enough to get into category 5 (107kt). I would assume that the BoM would have done the same analysis and came up with the same result.

11 years ago

It gets a bit confusing for a couple of reasons. One is that the Saffir-Simpson scale the Americans use doesn’t line up with the Australian scale, mainly because the Saffir-Simpson scale is effectively a 6-category scale (tropical storm, plus category 1-5 hurricanes); hence something at the bottom of the category 5 range in Australia is a high-end 4 in the Saffir-Simpson system.

The other confusion is about how winds are described. Peak gusts are easy enough but another indicator is ‘maximum sustained winds’. For this the Americans use a 1-minute average, most other places use a 10-minute average. The 1-minute maximum sustained winds are, on average, about 12% higher than the 10-minute. I’m assuming the numbers Davo’s quoting (given the source) are 1-minute, which converts to something around 110-115 kt for a 10-minute average, and in turn to 150-160 kt (275-290 km/h) for maximum gusts (usually about 40% higher than the maximum sustained 10-minute wind).

Davo’s right that the Bureau would be basing its analysis principally on the Dvorak technique. There’s a margin of uncertainty there, partly in the analysis itself, partly in how that is then converted to winds and central pressure, so it’s not difficult to imagine that the best estimate of intensity could be out by +/- 10% or thereabouts.

Assuming the same thing happens this time as after Larry, I would expect there will be a detailed damage survey after the event to try to estimate likely wind speeds on the ground. Road signs are particularly good for this sort of work because they’re standardised and amenable to wind tunnel testing.

Kevin Rennie
11 years ago

Cyclone Monica did hit a populated area. It was the indigenous community of Maningrida. For some reason it is a blind spot when the media talk about Oz cyclones. Still the strongest!

Monica ‘I’ witness.

11 years ago

Actually, Maningrida was too far away for the peak winds from Monica (a much smaller system than Yasi was) – the highest gust there was 148 km/h (from http://www.bom.gov.au/cyclone/history/monica.shtml), although I’m not sure exactly where the instruments are relative to the community, in a situation where 5km could make a big difference.

The destruction of vegetation at Monica’s landfall point, though, was truly spectacular.

11 years ago

As someone who went through Tracy may I offer some observations. The Tracy photo you show is, I would guess, of a new suburb where trees were not yet established. Not an indication of tree obliteration. I think leaves blowing off the trees is a good indicator of wind strength, but there needs to be some study of the relative strengths of sclerophyll trees vs. rain-forest trees. A most impressive indication from Tracy was the lamp poles (I think they were), probably 5 to 8 cm diameter steel pipes, gracefully bent over into C-shapes still sticking into the ground, with no evidence of impact from a hard object. one after another of them, in rows.

11 years ago

There seems to be too much dependence on the rather simple wind instruments used. Years ago I was involved in a yacht race that was hit by an intense low (TC Lance)off the east coast. The rescue helicopter told me that at times they had to apply full throttle just to maintain position over the yachts – something like +80 knots – yet the BOM maintained that the wind was gusting to 60 knots. Later on I talked to the lighthouse and asked them why the wind speeds were lower that actual, they replied that was the last recording before the instrument blew up.

Mark Textor
Mark Textor
11 years ago

A very interesting piece. I remember the trees stripped bare that morning. In fact its one of my most vivid memories of Tracy. Thanks for posting. Mark Textor

Russell Moore
Russell Moore
11 years ago

I was with the NSW SES at Cardwell, and I must say I was surprised at how well the buildings survived the cyclone.

One house that directly faced the beach, and had a tile roof, (admittedly every tile was wired down), only had about 10% of its tiles displaced. This house also had two roof mounted evaporative air conditioners, and only one had moved out of position. Quite a few buildings appeared to have little, no damage at all. One house we went to which just had a nailed down metal roof had about 35% of its roof peeled back, and folded over. I would have expected total roof removal at cat’ 5 wind speeds.

Also I would guess that about 40% of the towns trees are still standing, and almost 100% of the bushland trees are stripped bare of leaves, in fact it looked like a fire had swept through. Maybe this is how the local trees survive cyclones , most are only small to medium sized. If Cardwell had experienced a cat’ 5 I would have expected a lot more damage to buildings and more trees smashed or knocked down. RM

Scythrops Novaehollandiae
Scythrops Novaehollandiae
11 years ago

I am posting my question here as I have pretty much exhausted all
the sources of information on TC Yasi available in searching the Net.
I include Usenet in that sweep. None of the “social networks”
have been considered, at all.
My choosing the CT page to post to is based on the lead article, and
the follow up dialogue, as being the closest to what I know to be the
actual case for TC Yasi as at 1030AM on the 2nd of February 2011.
Assistance in getting the information I seek will be most
appreciated. One to one comms can be made using
Remove the obvious to get there.

Greatly concerned, I rang B0M in Melbourne (03) 9669 4054)
at 9AM on the 2/2/11 as the data from the Willis Met. site
and the SLP charts
were not giving me anything like the picture the output of the
TC Warning advices (for the previous 24 hours) had been building.
As I recall TC Yasi’s Sou’West quadrant (eye) at that time was some
50klms from Willis and running down straight onto Willis with a CP of
930+hPa and a MWS of 85-90 knots.
[The page had lost the klm/hr outputs
just after the radar went down at 8AM that morning]
I explained what I had found (previous 30+ hours)and asked the
very helpful officer to explain the anomaly for this supposedly
Cat#5 System.
That guy passed the question around the office, I could hear
the questions being asked as the others in the office bought
Willis up and obviously saw the screen output.
Nobody there could explain the anomaly.
I was passed onto a “Scientist” for an answer.
That person too had no answer other than suggesting I go read
a relevant work – http://www.worldscibooks.com/environsci/7597.html
At 444 pages I am now quite convinced pushing the question
was the best action on the day. My personal situation demanded
prompt action as the Govt. had ordered “mandatory evacuation”
for the immediate area I was concerned for, our home.
On pressing for an explanation, I was told, and I quote directly;
“This is our job, we are paid to deliver these advices and we know
what we are doing. You will just have to take a leap of faith in
trusting us, or, ask yourself are you prepared to live with the
outcomes IF you are wrong in using that data to make a decision”.
We had been lifting machinery and possessions to high places and
tying down movable objects since Sunday afternoon. With no answer
being the answer we decided to hightail it out of there before
the roads closed. That night we sat on a verandah and watched
TC Yasi move through, with no greater than 80 knot gusts. At that
location a Cat#3 storm was being touted. You do not sit outside
in a Cat#3 storm.
As with a number of other cyclones endured I was under the bed
for the few hours before the full force of TC Althea came upon us.
Seeing the damage already apparent, during the eye we moved
every mattress in the place to the shed on the property, closed
and bolstered the doors, huddling through the remainder when it came.
TC Althea was a Cat#3, in this new fangled “dumbed down” version of
storm rating.

On the morning of 5/2/11 I again rang B0M (Melb.) and asked if
they would pass the log on Willis Met. for the previous 72 hours up
until 11AM on the Wednesday, when Willis went “off-line”.
No problem there, the guy said he would get it and pass it on.
I am not going to detail the events between then and now, here.
The current status of that request is this – B0M (QLD) is refusing
to hand over the log. Information that is/was “public domain”.
B0M (QLD) has stated they will make a press release but no
data is being released at my request.

I am now asking myself “Why is that?”. Why is this information
now become “Classified”.
My question for any reader who has survived the text trip thus
far is — What do I do to discover why the information will
not be handed over?

I am now kicking myself rather soundly I did not take
screen-dumps as the information updated. I excuse that by
telling myself it was a busy time.
Why I am now pursuing this rather vigorously is for those
who come after us, those who will hear (anecdotally) what a
Cat#5 storm is like to endure, and what they will then do
to prepare themselves.
That worries me.. because in a true Cat@5 impact they are going
to die, or be severely injured.
TC Yasi was (at best) a medium Cat#3 storm outside of the 30K
“zone” around the core. At it’s core a Cat#4 at best, a low Cat#4.
True, in topographical area it was the largest yet, but that is
only relevant to the area the damage inflicted covered. A factor
we hear about every day as multiple communities deal with the
same scale of cleanup.

For the record?
As best as I recall, at 10AM on Wednesday 2nd February 2011
TC Yasi crossed onto Willis Isle with CP of 937hPa and a MWS
recording of 100 knots. The relevant changes in temperature
and humidity were present, as was the rainfall ceasing.
The site then recorded three instances of “CALM” followed
by at least four entries which were hyphenated (blank).
The page then fell over and a graphic was put up.
“No data available”. Subsequently the “no data for the
past 72 hours” resided up until the 18th of Feb/2011 when
the page was reinstated.

So far I have found just one person who was watching that
B0M page that morning. He “flicked off” after the radar
fell over, noting a MWS display of 185km/h. Although he
too is “anonymous” I am inclined to take his observation
as legit as it corresponds directly with what I know.

Two people watching Willis Met. station data updating in
real time?
It simply cannot be, not with ALL of Queensland and a greater
part of Australia being told the night before “the worst cyclone
in living memory is upon us, North Queensland… you are
on your own”.
This at 10PM Tuesday night and the eye of TC Yasi aimed
straight at Willis Isle, the earliest weather warning station
Queenland possesses.
Just cannot be.. but without that log of Willis’ Met. data all
of my post can be just written off as “constructed invective”.

What do I do to discover why the information will
not be handed over?
Please, somebody…
Storm Bird

Kevin Rainbow
Kevin Rainbow
10 years ago

Argue all you like with statistics and graphs etc, but, serving aboard HMAS Arrow in Darwin Harbour during Cyclone Tracy, all I know is our wind speed equipment failed at 260KPH, before the most severest of the storm hit us, and subsequently sunk us. So as far as I’m concerned, Cyclone Tracy will always rate as a severe catagory 5 system, and none of the so called scientific garbage will convince me otherwise. Being there is all thats needed.

Judy Wilson
Judy Wilson
8 years ago
Reply to  Kevin Rainbow

Kevin, I’m a 1968 Cav Rd graduate, and I think you were in 12 B. Our year group is having a 45-year reunion at Holland Park this Saturday 16 November 2013. Could you please reply to let us connect with you again? Five years ago we did a big search for everyone for our big 40th reunion, but sadly we couldn’t locate you – there were over 100 from our year on that night. This time there’ll be around 40 attending. Hoping to hear from you, Judy Wilson (nee Elsner).

Scythrops Novaehollandiae
Scythrops Novaehollandiae
8 years ago
Reply to  Kevin Rainbow

>Kevin Rainbow on April 4, 2012 at 7:18 pm said:
> So as far as I’m concerned, Cyclone Tracy will always rate
>as a severe catagory 5 system, and none of the so called
>scientific garbage will convince me otherwise.

As sorrowful as it is you lost your ship Kevin there is no correlation
shared in respect of the effects of a Cat5 blow on terra firma
infrastructure. Likewise for the sheer demolition of much of
Darwin residential, buildings largely thrown up with a wet thumb
into the wind and “she’ll be right mate” as the staples were shot
into the roof truss.
Nobody is going to challenge TC Tracy as the most severe system to cross our coastline in living memory, however there
is no reliable scientific data to learn from, surely the significant
point of Ken Parish’s post?
Other posts here on UTYH topics also lament the absence of any
science, “garbage” or otherwise.
My contribution points to the refusal to supply what was available,
clearly logged by BOM. As a reasonable conclusion that
refusal could be motivated from a read of the data proving the
extrapolation of the science denies the hype, hype built with an
ambition to garner disaster funding.
So here we are 37 years post Tracy with a score of storm events
since, and a Yasi to boot, and still there is no collective
coastal data grid/network for Northern Australia as a means to
gather the science. So it seems we are left to record only those
emotions of anecdotal opinion, all biased by each owned experience of what constitutes a “cyclone”..and therein lies
the rub.

>Being there is all thats needed.
And the starkness of it shocked you Kevin?
Not just leafless trees, as in Winifred/Larry/Yasi, but
NO BLOODY TREES… for miles and miles!
And in Town those giants that had stood for hundreds of years
uprooted and smashed into buildings that may have withstood if
100ton of timber had not smashed into them!
Who can forget the 10′ sheet of roofing iron buried a foot into the
trunk of an old eucalypt, a ‘flag’ 30′ off the ground? Standing there
on the side of the Stuart Highway just begging for a wag to scale
the height to paint – “WELCOME TO what was DARWIN”!

Sorry Kevin “being there” will not build ships capable of
withstanding Cat5 at anchor, neither will anecdotal subjective
values build improvements in warning and recording systems.
What “being there” will build is a heightened sense of impending
disaster for some, yet for others it will now be “oh I did Yasi
and yeah, scary, but no big deal really”… and that Kevin is
how science deniers will perish. At least they will not be able
to post about the experience afterwards, yeah?

As an update to my earlier post (February 26, 2011) I am yet to
receive any acknowledgement from any other user of the
BOM Willis Isle site on 2nd of Feb. 2011.
Also none of my endeavours to get BOM to cough with those
logs has borne fruit. At all levels the door just slammed
shut – why, remains my question.

Storm Bird

D Slater
D Slater
4 years ago
Reply to  Kevin Rainbow

I couldn’t agree more! Now all that’s left to do is to have the “unofficial” death finally known..! Have written a book about our experiences during and after Tracy. If you’d like a copy Kevin, email me, or post your contact details to PO Box 1097, Warwick Qld 4370.

D Slater
D Slater
4 years ago
Reply to  Kevin Rainbow

My comment “I couldn’t agree more…” was in relation to (and in full support of), Kev Rainbow’s comments. Love your YouTube work Kev..! Keep up the good work.