Wednesday, February 2, 2011


Central Queensland is about to, er, "receive" one of the biggest cyclones in living memory - Cyclone Yasi. It probably won't affect much us in Brisbane. However, being a flood engineer, I have collected some facts and figures. Also, being a pom, I have a genetic predisposition to talk about the weather...

The last cyclone like Yasi was probably Mahina, which occurred in 1899.

Yasi is so big, that if it hit America, it would cover the entire eastern seaboard from Newfoundland to Florida. If it hit the British Isles it would cover it from John O'Groats to Marseille.

Yasi is Category 5. It's a measure of severity There is no Category 6.

Yasi is expected to produce wind gusts of up to 280 to 300 km/hr, which equates to about 75 to 80 m/s. The eye has been travelling at about 30 km/hr, or 8 m/s. In a sprint, the fastest humans can run at about 10 m/s, and the speed of sound is about 330 m/s. So, you could hear it coming, but you won't be able to outrun it.

Yasi is expected to produce a storm surge of 6.5 to 7.0 m. That's the elevation of the sea above astronomical tide level (due to inverse barometric pressure). If it crosses the coast at about 3:00am tomorrow morning, it will coincide with a low tide, but if it waits until about 9:30 it will hit a high tide, which is about 2.5 m above mean sea level, resulting in sea levels about 9 to 10 m above mean sea level. Rule of thumb: if you're buying property in North Queensland, make sure it is at least 10 m above mean sea level. (Some residences in Brisbane are as low as about 3.5 m above mean sea level, but cyclones are much less frequent here).

Yasi is expected to dump up to about 1 m of rain as it passes in the next day or so. By comparison, the mean annual rainfall in Brisbane is about 0.9 m, and in the UK it's about 0.8 m.

All 250 patients in the Cairns hospital have been successfully evacuated to Brisbane.

About 20,700 people have taken refuge in Temporary Cyclone Shelters. The Shelters are now full, and Police are turning away latecomers.

At about 4:00pm, State Premier Anna Bligh announced that if you hadn't evacuated yet, you shouldn't try. Your best bet would be to hunker down in the strongest room in your house, which is usually the bathroom. Fancy spending the next 24 hours in your toilet? With no power? With all your family present?


  1. Received from Tony by email:

    2010/11 is developing to be record breaking on many fronts. We set new rainfall totals for the months of September, October, 30 years for November, and December 50 years {something like that anyway). Then the largest dump of rain 'known to man' in 20 minutes on top of a mountain range in January, followed by more 'SERIOUS" rain over the region to give us the 'little' flood escapade of a couple of weeks ago. If Wyvenhoe had not been there, we may have managed to exceed the 1893 flood, which I think is acknowledged to be the largest in 'Whiteman's' history.

    On a less myopic view we have the largest area of Australia being affected by flood waters throughout the interior recorded.(?) taking into consideration all that flowing into Lake Eyre from a few months ago to the extensive flooding throughout Qld, NSW and Victoria of recent days. Jump west and there are Fires.

    Expand the view finder and we have the floods in Brazil, the destruction of Pakistan (flood), and the early freeze in Europe. This does not even start to recount the Volcanic action.

    And this is all with God's promise not to flood the whole earth again.

    May we be gracious enough in our discussions to help friends and colleagues to see through the hype, and want to quietly sit down and read the Bible with us.

  2. Recieved from Sharon by email:

    Yikes, Martin, how scary for your Queensland neighbors! I have a question and I'm a bit embarrassed to ask (I think I should already know the answer but I don't), but what is the difference between a cyclone and a hurricane?

    I said a prayer for those in the path of the storm. May you and your loved ones be safe.

  3. My reply to Sharon by email:

    What's the difference between a buffalo and a bison? You can't wash your hands in a buffalo.


    According to Wikipedia (the font of all knowledge), a hurricane occurs North Atlantic Ocean or the Northeast Pacific Ocean. A cyclone is a tropical storm.

    I didn't know that until I looked it up.

    Incidentally, cyclones in the southern hemisphere go clockwise, but storms in the northern hemisphere go counter-clockwise due to the Coriolis effect (ignore that episode in the Simpsons - toilet bowls are not big enough for Coriolis to make any difference).

    The Good News is that Yasi came through without any major injuries or loss of life, though there has been extensive property damage in some townships, like Mission Beach. It seems like people did the right thing and got out of its way.

  4. Received from Roger by email:

    Thanks for info. Seen a little on the news. Let us know how you get on.

  5. Received from Mary by email:

    I "enjoyed" all the stats. As your pom cousin the weather never stops fascinating me but ... let us know when it's over - thinking of you.

  6. My reply to Sharon:

    I should add a "thankyou" for your prayers.

  7. Reply from Sharon by email:

    Thanks, Martin. I had a good laugh.

    Also, so happy to hear that prayers were answered — no major injuries or loss of life. What a merciful God we serve!

  8. My reply to Sharon by email:

    Though, tragically I heard a recent report of one 23 year old man dying from the fumes from his generator, and a married couple are missing from their yacht. Two other men who were reported missing have been found safe and well.

    The news is moving on now, and we're hearing about the blizzards in your part of the world.

    I hope you and yours are safe and well.