THE WELCOME heavy rain over many parts of drought ravaged Australia over the past month has been in part spurred by a strong weather driver that has allowed tropical moisture to feed into Australia.
Greg Browning, tropical climatologist with the Bureau of Meteorologist (BOM) said that while the Madden Julian Oscillation (MJO) did not directly cause the rain it was a significant factor in the falls, which although patchy, have given some farmers on the east coast their best falls in several years.
A strong phase of the MJO, a pattern of increased tropical convection which travels the world's tropical regions in an easterly direction, came into contact with Australia during a period when macro-climate drivers such as the Indian Ocean Dipole (IOD) and the El Nio / Southern Oscillation (ENSO) were both in neutral phases, meaning more local drivers, such as the MJO, can have a larger impact.
Over January there has been rainfall of over 600mm in parts of the Northern Territory and Broome and Derby in the Kimberley in north-west Western Australia have both recorded over 300mm for the month.
On the east coast there were widespread falls of over 200mm in the Tweed River region through far northern coastal NSW and the Gold Coast in Queensland, with 373mm at Miami, a suburb of the Gold Coast south of Surfer's Paradise.
Mr Browning said initially much of the moisture was confined to tropical regions, but said deep mid-latitude weather systems extended into the sub-tropics and drew down some of the moisture which was the source of the recent widespread rains across much of the eastern half of the country.
However, from here on, as the MJO passes, along with tropical cyclone Tino, over the Fiji region, creating a burst of westerly winds in the western Pacific, with potential to further warm parts of the western Pacific in the coming week or two, which is not conducive to rain in Australia.