Seasonal climate summary southern hemisphere (spring 2011): La Niña returns

Abstract

The southern hemisphere circulation patterns and associated anomalies for the austral spring 2011 are reviewed, with emphasis on the Pacific Basin climate indicators and Australian rainfall and temperature. Near neutral sea surface temperatures across the equatorial Pacific Ocean in winter began to cool in the spring, with the onset of La Nina conditions and below average subsurface temperatures. The Indian Ocean Dipole was positive, with cooler waters off the Indonesian coast but generally warmer than average temperatures over the Indian Ocean. Moderate positive values of the Southern Oscillation Index and negative values of the 5VAR index occurred, although not as strong as in spring 2010. Australia had much above average rainfall during spring 2011 (the ninth highest on record), especially in Western Australia, the Northern Territory and parts of South Australia, Queensland and New South Wales. Although below average rainfall fell in September over Australia, above average rainfall occurred in October and November, with every State receiving above average rainfall for November. Maximum and minimum temperatures were slightly above average over most of Australia, especially in Victoria, Tasmania, South Australia and New South Wales, and below average in the Northern Territory and Western Australia, where rainfall was higher.