Weather Patterns

There is several criteria that is used to determine the dates for Speed Week.

There are some weather patterns that have a significant impact on Speed Week. More specifically these are la Niña and el Nino.

The phenomenon named El Nino, means “boy child” after Jesus. The opposite effect, La Niña, means “girl child”.

A la Niña occurs roughly every three to seven years. So it is highly unusua to see two La Niña years in a row.

There have been 30 La Niña years in Australia since 1900, according to the BOM.
Back-to-back La Niña years have occurred 10 times.

The BOM ranks La Niña events by their intensity — weak, moderate or strong.
Australia's strongest La Niña years, 1917-18, 1955-56, 1975-76 and 2010-12, have all been part of multi-year La Niña events.
They have been associated with some of Australia's worst floods.

Speed Week has been cut short or cancelled in 1992, 1997, 2008, 2010-11, 2021-22 so there are definate parallels there.
In the summer of 2010-11 in Queensland, 33 people died, 29,000 homes were flooded and more than 78 per cent of the state was declared a disaster zone.
In March 2012, 75 per cent of NSW was under flood warnings.
It has been observed that the warming of the atmosphere is causing more extreme rain events. No two floods were the same and climate change was making them harder to model and predict.

A la Niña is caused by wind blowing near the Tropical Pacific pushes warm water that floats on the top layer of the ocean towards the east coast of Australia and Indonesia, drawing cold water up from below. With warmer waters surrounding parts of Australia, air can rise more easily and form clouds. In fact, in the warm months from December to March, the average rainfall for eastern Australia is 20 per cent higher during years when La Niña evolved.

While rare, La Niña is part of Earth’s natural climate cycle, and has been for millions of years.

Scientists have seen evidence of La Niña in ancient air bubbles found in ice that’s thousands of years old, in sediment pulled up from deep below the ocean floor, in coral fossils, and in tree rings.

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