The wet weather long promised by the La Niña weather system is finally being delivered … by the bucketload!
The ABC reports that a monsoon trough has developed off Australia’s north-west, and widespread rainfall and flooding is affecting northern and western Australia. More rainfall is expected across the tropics and down the east coast in the coming week.
Meteorologists say a climate driver known as the Madden-Julian Oscillation (MJO) is also having a large part to play. This is basically a large area of cloudiness and storms that moves around the tropics from the Indian Ocean.
When it is in its active phase, it creates a large upward motion that causes storms, convection and lots of rain. However, before and after the active phase comes the suppressed phases of the MJO, when large-scale downward motion in the atmosphere prevents lift and helps keep things dry.
The ABC reports that it is this downward motion over the past few weeks that has blocked the lift and rainfall we would usually expect with La Niña conditions for northern and eastern Australia … helping to keep things hot and dry.
The MJO was apparently quite active during November, when it was causing air to rise over the Indian Ocean but descend on Australia.
“That was part of the reason why our seasonal forecast … was going for a wet northern Australia but November ended up being relatively dry in many locations across the north,” Dr Matthew Wheeler, principal research scientist at the Bureau of Meteorology (BOM), told the ABC. “Right now, even though it’s borderline weak/strong, it’s more favourable for letting the wet season get under way again in northern Australia,”
The BOM’s outlook for summer suggests there is still a high likelihood of above-average rainfall for much of the country.
Here in Logan City / Brisbane Qld. it has been raining for well over 24 hours. I do not know if the rain has caused any flooding, but it sure is a welcome to our area.
Hope it has reached the area on the other side of the Great Divide.
John Rodgers