Often you will hear about trade winds, and you probably wonder what that is. Well for Queensland it is where we get a high-pressure system that sits over South Eastern Australia, and circulates air approximately anti-clockwise. This means it moves North parallel to the East coast of Australia and at some point heads back to the coast.
To begin with, the winds come more from the SE along the North Queensland coast, and there are a few locations that are more exposed to the SE winds such as Innisfail and Mackay/Whitsundays. So during winter, you might think there should be not much rain at all but these two locations can see a lot of rain.
As the High moves further East, the winds are directed to the coast from a more Easterly direction. The winds change from dry cool air to warm humid air as the ocean further North is warmer and thus evaporating more moisture into the atmosphere. So the less exposed regions will start to see some rain, such as the Burdekin, Hinchenbrook and Cairns and maybe even Townsville. Sometimes the High has a bit of a bump where the air travels from the SE, and does a sharp turn before the coast to come from the NE. This is called a ridge, and it can prevent rain from crossing the coast.
It is interesting to note that the trade winds are one of the factors in determining an El Nino, and currently, the trade winds are still around average, and they need to be below average to tick one of the four boxes to achieve El Nino in our region.
Any three of the following criteria need to be satisfied:
Sea surface temperature: Temperatures in the NINO3 or NINO3.4 regions of the Pacific Ocean are 0.8 °C warmer than average.
Winds: Trade winds have been weaker than average in the western or central equatorial Pacific Ocean during any three of the last four months.
SOI: The three-month average Southern Oscillation Index is –7 or lower.
Models: A majority of surveyed climate models show sustained warming to at least 0.8 °C above average in the NINO3 or NINO3.4 regions of the Pacific until the end of the year.
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