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.
After a few cold mornings, the cold days have now started in the ACT.
Snow has fallen across large parts of NSW, including the Blue Mountains, parts of the NSW Central Tablelands, and in the Barrington Tops National Park near Gloucester.
Sydney's run of cold weather has continued today but when can we expect it to warm up? Considering last autumn was the warmest on record the past few wintry days have been a shock to the system for many.