Atmospheric indicators, including the Southern Oscillation Index (SOI), trade winds and cloud, also show clear La Niña patterns.In order for 2017–18 to be classed as a La Niña year, the event needs to last for at least 3 months.Areas of stronger warm anomalies in excess of one degree above average were observed surrounding southeastern Australia and the South Island of New Zealand.
La Niña can also increase the chance of prolonged warm spells for southeast Australia.
Cloudiness near the Date Line remains below average (positive OLR anomalies).
Cloudiness values have been generally below average since early August.
All three NINO indices were cooler than October values.
The 30-day Southern Oscillation Index (SOI) to 3 December is 11.1 (90-day value 8.9).