Oz Cyclone Chasers Cyclone Blog
ENCOURAGING LONGER TERM CLIMATIC INDICATORS FOR THE AUSTRALIAN REGION
Firstly there are two very dominant influences on our weather, one is the Indian Ocean to our west and the Pacific to our east. Unfortunately, late in 2015 we faced a double whammy for suppressed conditions in Australia with the onset of a very strong El Nino in the Pacific and making matters worse, a positive Indian Ocean Dipole (IOD) in the Indian. A positive Indian Ocean Dipole is where cooler waters exist in the East Indian Ocean Region compared to the West resulting in generally higher pressure (suppressed conditions) over both Northern and Western Australia. The Positive IOD broke down in December however, the strong El Nino in the Pacific which also contributed to suppressed conditions over Australia tightened its grip.
The below diagrams sourced from the BOM give you an idea of what effects the Positive Negative IOD have on our region. A negative IOD is obviously what we want to see develop and the good news is that global computer models are becoming increasingly confident that this could occur closer to spring and be a strong one too. A copy of the BOMs Indian Ocean Outlook, a compilation of model data is attached and shows whats going on, the dotted line is the mean with the thinner lines being the outliers. You don't need to be a rocket scientist to work out that overall trend is towards a negative event occurring and this is great news for Australia particularly if it occurs earlier in the Spring.
So where to from here? Well as we move closer to spring, if a Negative IOD is in full swing we should start to see a much higher chance of rain through both Western and Central regions of the country, while the influences on Northern Australia are not as pronounced and not fully understood, a negative IOD does help by maximising moisture available. While of course there are other factors at play that contribute to rainfall, the BOM graph below shows what can happen during a negative IOD event which usually peak late in the year, in this case it was 1975 when songs like Mamma Mia from ABBA were topping the national song charts!
If this is not encouraging enough for you we also look at the Pacific Ocean forecasts and they too indicate are looking very positive for us with Neutral and in some cases a La Nina developing (50%). The BOM have said that it is extremely unlikely a repeat El Nino will occur next summer so again this is good news. For those that don't know, La Nina is when the Central Eastern Pacific Ocean cools leaving warmer waters in the Western Pacific near Australia. Trade winds increase as pressures tend to lower around our region bringing greater rainfall to the country. Below are the global computer models forecasts for the Pacific which we call the ENSO region, you can see that a neutral state is favoured but there are some models showing La Nina developing, moreso into early next year (not displayed). A good La Nina example was back in 2011 and the BOM graph speaks for itself, that year we had a slight negative IOD that spring too. While we are not suggesting another 2011 will occur it certainly demonstrates what is possible when things align.
All in all, the weather will be the weather, but amongst some of the doom and gloom of late it is good to look at the brighter side and we are definitely seeing some encouraging early signs of what 'might' be around the corner. All of this stuff can be found in much greater detail if you go to http://www.bom.gov.au/climate/about/?bookmark=introduction. The BOM have done an exceptional job at trying to explain most of Australia's main climatic influences.