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The deluge was totally predictable, so why weren't we warned?

By Keith Kennelly - posted Friday, 14 January 2011


Do you remember the storms in Bass Strait during the Sydney to Hobart? That’s where they originated. These rain depressions are a quite normal event for Queensland coasts and hinterlands.

Third an upper level Australian East Coast Low had formed over Christmas off Bundaberg.  These commonly form in Harvey Bay or off the coast at Coffs Harbour and usually blow themselves out at sea or can track south west inland. They act very similarly to cyclones in many ways but without the extreme winds. Winds can blow up to 50 knots.

Cyclones typically deposit most of their rain not on the coast but about 100 kilometres inland. It takes a little while for the air to cool sufficiently for condensation to form (See later). This Low was a result of the cooler SE trades coming into contact with The Australian East Coast Current flowing down from the warmer Coral Sea. This current warms the air, causes it to rise, in turn causing further cool air to come in, rapidly, whipping up the sea spray and causing it to warm and rise.  They do pick up huge amounts of sea water.

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On a personal note I was once caught in a yacht in Harvey Bay while one of these East Coast Lows formed. The winds gusted up to 50 knots. The lasting impression I had, besides the humidity, was that I could not see beyond the pulpit of the yacht from the cockpit because of the spray coming off the ocean. The amount of moisture in the air was astonishing.

This latest current Low had travelled up and down the coast for a week, until it went ashore at Fraser Island last Monday, tracked southwest from TinCan Bay, through Maryborough, Blackbutt Ranges, Sommerset and Wivenhoe Catchments, the Lockyer Valley, Toowoomba, Bremer catchment and Dalby through to the Granite belt. It deposited the greater part of its massive load, about 100klms inland, over the Lockyer Valley and Toowoomba. 

Here I feel it appropriate to explain how rain is caused. Rain/precipitation is condensation. If you look at your car windscreen you will often see condensation (warm air cooling) but there are no rain drops in your car.  To form raindrops/precipitation, condensation must form on something. Usually it is dirt or dust particles in the air. In most rains at sea and in particular tropical cyclones it is salt particles in the air, from the evaporated and warmed water, that enables raindrops/precipitation to form.

So what happened at Toowoomba was a combination and an unusual convergence of three quite normal Queensland weather events. Principally an East Coast Low crossing the coast at Fraser Island and Tin Can Bay and tracking southwest through Toowoomba, second a SE Trades rain depression tracking westward from Brisbane to Toowoomba and third the previous severe soaking effects from a traditional North Queensland Monsoonal trough.

Questions do need to be asked.

Why wasn’t the deluge in Toowoomba predicted by the Bureau of Meteorology? Why were local "Severe Weather Warnings" not issued to the media and broadcast before the Toowoomba deluge, as had been regularly issued throughout the rains in other Queensland areas?

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Why didn’t State Emergency Services undertake preparations for flooding?

It was obvious the East Coast Low had crossed the coast as downpours had flooded Tin Can Bay, Gympie and the North Coast Hinterlands on the Monday morning. It should be noted warnings were issued in Gympie enabling retailers to remove stock.

It also needs to be asked why many, from the Queensland Premier Anna Bligh down, in the media are now saying the downpour in Toowoomba wasn’t predictable?

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About the Author

Keith Kennelly is a 53-year-old small business operator, resident in Brisbane who raised two childern as a single dad. His hobbies now include swiming, reading, sailing and Texas Hold 'Em poker.

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