Who is this El Niño guy? Why does he hit Aust so hard?
HE'S a little boy who traditionally arrives around Christmas time - but El Niño is no saviour.
The global weather phenomenon, named in Spanish as "the little boy" (a reference to the Christ child), has the potential to bring disaster.
The Bureau of Meteorology explains that the term refers to the extensive warming of the central and eastern tropical Pacific Ocean which leads to a major shift in weather patterns across the Pacific.
This occurs every three to eight years and is associated with drier conditions in eastern Australia. El Niño Southern Oscillation (ENSO) is the term used to describe the oscillation between the El Niño phase and the La Niña, or opposite, phase.
During El Niño years, the Pacific trade winds weaken and the central and eastern tropical Pacific warms up, causing that area to become more favourable for tropical rainfall and cloud development. The heavy rainfall that usually occurs in our north moves to the central and eastern parts of the Pacific.
A recent report from the bureau says this El Niño is the strongest seen since 1997.
"Its equivalent in the Indian Ocean - the positive Indian Ocean Dipole (IOD) - is now at levels not seen since late 2006," the bureau says.
"The strong El Niño is expected to last until at least the end of the year before declining in the first quarter of 2016, however the positive IOD is expected to decay this month.
"Sea surface temperatures in the central to eastern tropical Pacific continue to warm, further entrenching El Niño ... waters to the north of Australia have also cooled, which may further contribute to drier conditions."
Most international climate models surveyed by the Bureau of Meteorology indicate the anomalous warmth in the tropical Pacific Ocean is likely to peak around the end of this year.
El Niño is associated with both an increase in individual extremely hot days and multi-day warm spells.
Potential effects of El Niño on Australia include:
- Reduced rainfall
- Warmer temperatures
- Shift in temperature extremes
- Reduced tropical cyclone numbers
- Later monsoon onset
- Increased fire danger
El Niño facts
- Happens every 3-8 years
- Trade winds weaken, Pacific warms up
- Combines with other factors to reduce rainfall
- Storms, fires are likely