Big wet 2020 looms for Central Queensland
CENTRAL Queensland is set to receive well-above average rain in winter and spring as a rare weather combination develops in the Indian and Pacific oceans.
Sky News Chief Meteorologist Tom Saunders is one of the forecasters closely monitoring ocean temperatures at what he described as "a critical time of year".
The current pattern of modelling for the two oceans has only occurred five times over the past 60 years and the last time that occurred was in 2010 when the nation experienced its wettest 24 months on record with major flooding including a 9.2m Fitzroy River flood in Rockhampton - the third highest in the city's history.
"There are early signs that 2020 could provide a La Nina or a negative Indian Ocean Dipole or possibly both," Mr Saunders said on the weekend.
"The latest modelling data in the Pacific Ocean shows that out of 8 global models, by winter three predict La Nina conditions to form. That brings rain to Australia. Five predict neutral and no models predict El Nino. That's good because El Nino is what brings us drought."
In the Indian Ocean, out of seven global models, seven predict that by August there will be a negative Indian Ocean Dipole (IOD), no neutral and no positive forecasts.
Mr Saunders reminded us that it was a positive IOD that brought a very dry finish to Australia in 2019.
He said that when there is a negative IOD most of Australian experiences above average rain but when that combine with a La Nina event, the rain possibility is enhanced even further.
What causes La Niña?
La Niña occurs when equatorial trade winds become stronger, changing ocean surface currents and drawing cooler deep water up from below. This results in a cooling of the central and eastern tropical Pacific Ocean. The enhanced trade winds also help to pile up warm surface waters in the western Pacific and to the north of Australia.
The warming of ocean temperatures in the western Pacific means the area becomes more favourable for rising air, cloud development and rainfall. As a result, heavy rainfall can occur to the north of Australia. Conversely, over the eastern and central tropical Pacific, air descends over the cooler waters, meaning the region is less favourable for cloud and rain. The air rising in the west and descending in the east enhances an atmospheric circulation - called the Walker circulation - which can result in changes to the climate felt across the globe.
The Indian Ocean Dipole
Warmer sea surface temperatures in the western Indian Ocean relative to the east
easterly wind anomalies across the Indian Ocean and less cloudiness to Australia's northwest
less rainfall over southern Australia and the Top End.
Cooler sea surface temperatures in the western Indian Ocean relative to the east
winds become more westerly, bringing increased cloudiness to Australia's northwest
more rainfall in the Top End and southern Australia