The NINO3.4 index is one of several El Niņo/Southern Oscillation (ENSO) indicators based on sea surface temperatures.
NINO3.4 is the average sea surface temperature anomaly in the region bounded by 5°N to 5°S, from 170°W to 120°W. This region has large variability on El Niņo time scales, and is close to the region where changes in local sea-surface temperature are important for shifting the large region of rainfall typically located in the far western Pacific.
An El Niņo or La Niņa event is identified if the 5-month running-average of the NINO3.4 index exceeds +0.4°C for El Niņo or -0.4°C for La Niņa for at least 6 consecutive months.
Photographs of weather phenomena around Australia, some of them capturing rare events, have been chosen for the 2017 Australian Weather Calendar.
Perth is enduring a sweaty end to the week, although a cool change is on the way.
While most Queenslanders sheltered inside during the past week of severe storms, a breed of professional photographers known as storm chasers were outside, braving the danger to get the best possible shot.