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.
Parts of South Australia have woken up underneath an intense low pressure system today, less than 24 hours after severe thunderstorms cut power across the state.
About 90 per cent of South Australian households have had power restored after yesterday's state-wide blackout as damaging winds and stormy weather continues.
Tasmanians are being warned to prepare for wind and rains forecast to lash the state on Thursday.