Global Setting – September 2012

The Pacific Ocean is still close to El Niño thresholds, but the atmosphere has yet to show patterns typical of El Niño. The global forecast models indicate the conditions are likely to remain close to thresholds or transition towards a weak and short-lived El Niño over the next three months. For New Zealand however they do not show signs of the southwesterly and westerly anomalies that are usually associated with El Niño events. Higher than normal pressures are expected South of Australia and New Zealand at the mid-latitudes, and lower pressures than normal are forecast to the north of the North Island. This pattern is expected to be associated with weaker than normal westerly flow over the country. 

Sea surface temperatures

Sea surface temperatures are expected to be warmer than normal around the South Island, and cooler than normal to the east and north of the North Island. 

Differences from average global sea surface temperatures for 2nd September to 29th September 2012. Map courtesy of NOAA Climate Diagnostics Centre (http://www.cdc.noaa.gov/map/images/sst/sst.anom.month.gif).
Monthly values of the Southern Oscillation Index (SOI), a measure of changes in atmospheric pressures across the Pacific, and the 3-month mean (black line). SOI mean values: September SOI +0.2; July to September average -0.2.
Differences from normal September surface temperatures in the seas around New Zealand.