How should we measure cyclones? And was Tracy really bigger than Larry? Crikey readers respond:

Jim Birch writes:

Re: Larry v Tracy: How do scientists compare cyclones? (Yesterday, item
2). Tony Ryan complains that scientists don’t install wind speed
indicators where they won’t be damaged by cyclones! Well mate, they
do. Example: Hobart. Unfortunately, if you install one anywhere
where it gets a direct hit from a cyclone it’s going to fail – there’s
just so much high speed junk flying around. And why do meteorologists
give the highest recorded windspeed before failure as the highest
recorded windspeed? Because it is. Science is not
speculation. It’s not a competition between mayoral estimates.
And how do you really measure wind speed in cyclones? Actually
you can’t very well. The usual meteorological methods fail. There’s the
highest recorded speed till something hits the
anemometer. There’s some radar evidence. There’s a
methodology of examining an array of physical evidence like the depth
of penetration of flying grass stems in wooden posts and so on. But
the problem is that the windspeed in a cyclone isn’t constant, it’s
extremely gusty, varying enormously over short spaces and times. The
centres of at least some cyclones are believed to contain tornado-like
systems so it could be the tornado in the cyclone – a relatively brief
small scale event – that actually delivers the knockout punch.
Cyclones
are not well understood, especially in their wild centres. Let’s just
say it’s hard to research. “Category 5” says enough for most practical
purposes.

John Goldsworthy writes:

Your correspondent, Tony Ryan
reiterates the claim which was common after Tracy that the cyclone
described an “S” path through Darwin. This claim was based on points of
intense damage along the path. From the air there was no proof of
that theory. The path of Tracy described a gentle curve which pretty
well followed the Sturt Highway until it dissipated around Humpty Doo.
No serious credence has yet been given to the other possibility that
the points of intense damage could have been caused by tornadoes
contained within the cyclone. Two instances, which I observed,
lend support to that theory: 1) A Ford Falcon firmly lodged in the wall
of the Travelodge Motel at the first floor level, and 2) A dent in the
Rapid Creek water tower tank apparently caused by a refrigerator
which was found lying at the base of the tower. The height of the
water tank would have been about 60 feet. These were only two of
several which I heard about but were the only ones which I actually
saw. In respect to the sandblasting of motor cars I can attest to that;
our station wagon was sandblasted down to bare metal on the seaward
side and we were about 5km from the sea on the RAAF Base. The
rest of Tony’s comment is fairly accurate. Other significant trivia
include the fact that the barometric pressure went off the recording
paper at 847 millibars and the maximum wind speed was estimated
(because the anemometer maximum speed was exceeded not because of
material damage) at 240 knots which is about 480 kilometres per hour.
The damage bill for Tracy was about $800+ million. Which brings
up another subject: where did all the donated money go? We lost
everything but our claim for assistance was refused because we had
insurance. Not that the insurance covered all that much and some things
have sentimental value only. Memories grow dim with time except for
those who went through it. Larry might have covered a wider area than
Tracy but I believe that it will be some time before her
destructive power will be exceeded.

John
Richardson writes:

I’m no scientist but I think
Tony Ryan is pretty right in his observations, except for a couple of
points. Tony says that between 70-90
people died in Darwin although, if I recall correctly, the “official” death toll
was only 52? I don’t know what Tony would say
to my comment, but when I was working for the Reconstruction Commission in
Darwin after Tracy, there was a lot of talk about the number of casualties
being closer to 500. It was suggested that the authorities could only really
account for public servants, ratepayers and others in the community with
formal links, whilst itinerants, hitch-hikers, Aboriginal people, native
fishermen and even yachtsmen in Darwin harbour and around the coast couldn’t
be accounted for. The power of such natural events
is awesome: I saw sheets of wrought iron wrapped around trees like silver foil
around a chocolate bar; 20′ steel telegraph posts lying on slabs, where if you
looked back through a row of houses, you could see where the poles had torn
through them like a javelin. From the air, parts of Darwin looked like they’d
been destroyed by bushfire. Whilst there is no doubt that
Larry is a tragedy of the first order for the people of QLD, I don’t think it
was on the same scale as Tracy.

Terry Kidd writes:
Basically I agree with Tony Ryan’s assertions about cyclones and
Cyclone Tracy in particular. However neither
Larry, nor Tracy, were the strongest cyclones to strike Australia in
modern times. Cyclone Joan which hit Port Hedland in WA in early 1975
and totally demolished the town, including bending tripod electricity
poles made of railway line steel parallel to the ground, was easily the
strongest. Joan got very little publicity because the public and media
were all concerned with Darwin. I recommend that when people tour the
great Northwest that they take time to visit the local museum in Port
Hedland and view photographs of the destruction. Even Tony Ryan would
then agree that Joan was a smashing lady.

A Cairns City Council worker writes:
In response to Tony Ryan’s comments in yesterday’s Crikey
I would like to respond to his very untimely and unnecessary article. During Cyclone Larry I worked in the Cairns and
region Disaster Co-ordination Centre for a period of 48 hours. Myself and most of the team involved in the centre
were horrified that an article comparing and belittling our residents’ plight at
this time would be published. I agree with Tony’s comments on the science issues
associated with cyclone categories however he then bemoans this issue and misses
the real point that this is about the destruction of people’s lives, not
buildings and cars. At a time when all the available support is required by this
region, does it not seem juvenile and irresponsible to publish an article
nullifying the impact this cyclone has had on people?

Peter Fray

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