Monsoon set to break
The last couple of months have seen a triple whammy of climate factors leading to widespread death and destruction right across the country.
The combined impacts from one of the strong positive Indian Ocean Dipole (IOD) events on record, a Sudden Stratospheric Warming (SSW) event and flow on strong negative Southern Annular Mode (SAM) events have resulted in 2019 being the hottest and driest year for Australia on record.
In short, the lack of moisture from the Indian Ocean and lift in the westerly storm track towards the country from the south has brought hot, dry weather - and devastating fire conditions.
One additional flow on effect of the strong positive IOD event was that it blocked the development of the monsoon trough across the north of the country, effectively holding it at bay until now. The onset of the monsoon usually occurs late October and into early November, bringing enhanced rainfall across northern Australia.
To categorise, the onset of the monsoon is confirmed when rainfall totals across the north of Australia reach 50mm from the 1st of September. While some locations were only slightly late this year, the majority of the north of the country has seen the monsoon delayed significantly with higher than normal temperatures in Darwin due to the lack of cloud and moisture. However, it's now breaking. This is also the reason for the record breaking heat into the last weeks of December, with the interior of the country being mostly cloudless allowing massive amounts of heat to build up.
With the IOD event steadily weakening and breaking down since its peak in late October, we're finally set to see an increase in tropical activity and rainfall across northern Australia.
The Madden Julien Oscillation (MJO) gives an indication of where this wave of tropical activity sits around the world, and also its strength. The MJO is monitored and forecast out to two weeks by various weather agencies around the world, and can be visualised on the charts shown below.
While it looks quite complicated, it's actually fairly simple. The globe is set up into eight rough sections, and if you imagine looking at the diagram from the south pole, you can see Australia falls in the middle of section 4/5 (Maritime Continent), 7/6 covers the Pacific Ocean, 8 America, 1 Africa and then back to the Indian Ocean 2/3.
The MJO was located in the Western Pacific at the end of December, leading to the formation of Tropical Cyclone Sarai late last week, but has since weakened and moved east.
The MJO is forecast to continue east and strengthen in sector 4/5, our continent. This will influence the north-west of the country, bringing with it enhanced tropical cyclone potential and increased rainfall.
Looking at the long-range model forecasts and there's plenty of activity on the cards for the Timor and Arafura Seas with a couple of cyclones possibly forming over the coming fortnight. The swell prospects for Australia will be limited to the north-west facing coasts off Western Australia, but eastern Indonesia looks to receive a large, close-range swell but with strong westerly winds.
The tropical activity won't influence the East Coast until the MJO moves further east, and only if it maintains its strength. We'll keep an eye on the outlook for WA and the Eastern states in the Forecaster Notes over the coming weeks.