The NINO3.4 index is one of several El Niño/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 Niño 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 Niño or La Niña event is identified if the 5-month running-average of the NINO3.4 index exceeds +0.4°C for El Niño or -0.4°C for La Niña for at least 6 consecutive months.
Severe weather predicted for Tasmania's north and east on Friday has prompted a public warning from emergency services.
Rain and storms could bring flooding to parts of southern and southeast Australia during the next 24 hours.
People in Darwin and other parts of the Top End may be about to get relief from recent hot weather, with the Bureau of Meteorology (BOM) predicting a monsoon trough will start to affect the area within days.