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.
The full devastation brought on by Tropical Cyclone Debbie will not be known until the morning, Queensland Premier Annastacia Palaszczuk has warned, as the system is further downgraded to a category two.
Cyclone Debbie has been downgraded to a category two system after crossing the north Queensland coast.
Tropical Cyclone Debbie has been downgraded to a category three system, having made landfall along the north Queensland coastline near Airlie Beach earlier this afternoon as a slow-moving category four system.