keith,
From general experience with more cyclones than I care or want to remember, I tend to think strong wind gusts during a cyclone do the most damage, as well as storm surges and flooding from rain.

If a cyclone is category 3 and above, it is dangerous, and strong buildings are necessary, with expected loss of electricity supply to some or most areas in the cyclone path.

Category 4 is worse, and category 5 basically requires mass evacuation.

What happens afterwards is perhaps more important, as power has to be restored, roads cleared, fuel made available, bridges repaired and food delivered.

The author maintains that good organization occurred. I think that there was good organization for a cyclone that hit a small population, but if Yasi had hit a more populated area, the situation would have been very different, and the armed forces would have been required.

If the roads are cut, the army cannot get through. If the air port is out, the air force cannot land planes until they can get the air port operational.

The navy could get ships into the area, but most of our navy is currently non-operational and unreliable, and would be of little use to supply aid to a large population.

Vanna,

You are right to say that it is the severe wind gusts that do the most damage during cyclones.

Larry's cat 4 severe gusts were recorded at 181klm/hr and they destroyed much.

Tracey's severe gusts were recorded at 217klm/hr and they destroyed totally.

Now given how wind speeds are calculated in cyclones [See Tracey Official report for info on how that is done (pages 45 approx)] Yasi's sustained winds (1 min) should have been at 240klm/hr for over 80klms from the edge of the eye, and given your experience can you please explain to me how anything was left standing from Ingham to Innisfail if Yasi was indeed a cat 5 cyclone?

Please note that sustained winds in a cyclone are multiplied by a factor of 1.2 to ascertain the stronger wind gusts. Sustained winds are gusts that last for one minute and longer...which means all the winds within 80 klm of the eye in Yasi would have been stronger than anything you've ever experienced in any cat 4 or lesser cyclone.

Surges are caused by the action of wind, wave and tide. The stronger the winds the bigger the surge.

Now please tell me why Cat 5 requires mass evacuation?

As far as organisation of the rescue operations, I think you're kidding yourself. I was talking to one of our SES volunteers yesterday, & he was totally scathing of the organisation.

He was one of 80 very experienced SES volunteers from SEQ who flew into Cairns to help out. First they were horrified to find the transport organised for them was a fleet of hired Toyota Camrys, not quite ideal for flooded, littered & damaged roads.

Despite this, it was not the army with their high clearance 6X6 trucks that were first into a number of the isolated coastal communities, it was "the charge of the Camrys" that led the way. In some instances the media were in the lead, but at least they had 4WDs to drive.

Fortunately, some of them had a fair idea of what to expect, as they got no useful support locally. What they took with then was it, even down to fuel for the chain saws.

Organisation, what's that? Perhaps that what left Horseshoe Bay, on Magnetic Island, off Townsville, without help for so long.

Yes that's right, Townsville, a long way from the centre.

This cyclone was like a number I have experienced. A moderate, very large system, with pockets of very severe storms embedded within it. Those who got those pockets probably had true Cat 5 strength. This is where the false claims of Cat 5 are coming from. Of course the pollies jumping on the biggest claim they can find to build their drama. This makes it hard for the BOM to then tell the truth.

Keith,
"Now please tell me why Cat 5 requires mass evacuation?"

In most of our towns, people cannot live for very long without electricity.

They will have no drinking water, lighting, cooking facilities, food refrigeration facilities or sewagage disposal.

A cat 4 cyclone can mean large areas will be without power for many days or a number of weeks (and I was on the edge of a cat 3-4 last year and some areas were without power for 2 weeks afterwards)

A cat 5 cyclone going over a town will not only wreck many buildings, it is likely to wreck most of the electricity supply lines also making it impossible for most people to live in the town afterwards.

Hasbeen,
It is interesting that the SES were called into Townsville when Townsville has a large army base.

The current situation with the navy is that it is unreliable in an emergency, and perhaps the army is just as unreliable also.

WTF?

Seems like someone has cyclone envoy – my cyclone is bigger than your cyclone.

Grow up you poor sad creatures.

'A cat 5 cyclone going over a town will not only wreck many buildings, it is likely to wreck most of the electricity supply lines also making it impossible for most people to live in the town afterwards.'

And that didn't happen in most of the Cassowary coast nor in Ingham, Townsville, Innisfail nor Cairns. Only 105 buildings were destroyed. Compared to 9000 in Tracey. And there was no great exodus because the region was unliveable whereas 2/3 of the pop of Darwin was evacuated.

So where was the cat 5 cyclone?