Queensland Floods; Inland Tsunami; 8-metre wall of water

[Ban my account ffs!]

It seems that there is little surprise that major floods occurred in 1974 and again this year, considering both years have had powerful La Niña conditions in the Pacific ocean.

The combination of very strong trade winds (compared to normal) plus warm water being pushed up against Australia has caused convection to increase dramatically when that warm, moist air reaches land.  The result is quite obvious.

The La Niña continues to rage and I'd expect that above normal precipitation will continue across eastern Australia.

[Ban my account ffs!]

Some nice illustrations to show the causes behind these floods:

"Normal" conditions in the Pacific ocean: (I use the term normal very loosely as such conditions, while representing an average, are not all that common during Sept-May.  The last such period with "normal" conditions was 1996/97.)


Air pressure is higher in the central Pacific near Tahiti and somewhat lower at Darwin, Australia.  The trade winds carry warm water and moisture westward to Australia where they cause convection near the Australian coast, bringing summer rainfall to the region.  (Winter in the northern hemisphere).  Cooler water upwells near South America and keeps that area much drier.


El Niño:  During El Niño, the pressure near Tahiti becomes lower than normal and pressures rise near Darwin.  In extreme events, this can actually cause the trade winds to reverse.  This brings dry winds from the Australian outback and starves eastern Australia of precipitation, resulting in drought and more bushfires.


La Niña:  During La Niña, the pressure near Tahiti rises and concurrently falls near Darwin.  This increases the trade winds.  It also bunches up very warm water near the coast of Australia.  The air getting this injection of extra moisture is carried further inland than normal where it rises and forms thunderstorms/rain.  This year has been an extreme example of that, and the scale we use to measure the atmospheric strength of the El Niño/La Niña cycle has broken records.

In fact, the most recent data shows a pressure of 999.5mb at Darwin with a pressure of 1013mb at Tahiti... resulting in a Southern Oscillation Index of 39.  It could go higher yet.  In December, the monthly SOI of 27 was the highest ever recorded for December and the highest of any month since November of 1973.  What happened in Australia during the summer of 1973/74?  Do you see where I'm going with this?

I really hope people get a chance to dry out... but things don't look good.  Hang in there.  As with everything, this, too, shall pass.

[Ban my account ffs!]

http://www.bbc.co.uk/news/world-asia-pacific-12260724

The floods are still affecting many near the northern Victoria border as the moving "inland sea" slowly moves down stream.

For the moment it appears much of eastern Australia is dry... a much needed break at least for the affected regions.