Seasonal climate summary southern hemisphere (winter 2010): A fast developing la Niña

Abstract

Southern hemisphere circulation patterns and associated anomalies for the austral winter 2010 are reviewed, with emphasis given to the Pacific Basin climate indicators and Australian rainfall and temperature patterns. Winter 2010 saw the fast development of La Niña conditions across the Pacific Basin, a rapid transition from the El Niño conditions in place during summer 2009-10. By the end of winter 2010, most ENSO indices were displaying a La Niña signal, with the equatorial Pacific Ocean surface and sub-surface cooling during each month of winter. The Southern Oscillation Index (SOI) became more positive over winter, with an August value of +18.8. In the extra-tropics, a very strong positive phase of the Southern Annular Mode (SAM) was in place for most of winter 2010, with June and July both recording their highest positive monthly SAM index values on record. In the Australian region, rainfall was generally average to above average. However, in contrast to the rest of the continent, southwest Western Australia had its driest winter in 111 years of records. Temperatures tended to be cooler than normal across southern Australia, and warmer than normal in northern Australia.