Seasonal climate summary southern hemisphere (summer 2008-09): a weak, brief La Niña returns. Bumper wet season in tropical Australia; exceptional heatwaves in southeastern Australia

Abstract

Southern hemisphere circulation patterns and associated anomalies for the austral summer 2008-09 are reviewed, with emphasis given to the Pacific Basin climate indicators and Australian rainfall and temperature patterns. Atmospheric and oceanic indicators re-intensified to briefly reach weak La Niña levels during the austral summer 2008-09, with the event clearly of lesser magnitude than the mature 2007-08 La Niña event. A rotated ‘V’ pattern of warm anomalies in the western Pacific surrounded a cool equatorial tongue in the central and eastern Pacific. A positive phase of the Southern Oscillation was maintained throughout the summer, with cooler than average sea-surface temperatures in the NINO 3 and 4 regions. Strong warming in the western equatorial Pacific suggested that this La Niña would only be of short duration, with weakening of central Pacific cool anomalies noted in February 2009. Two exceptional heatwaves in southeastern Australia in late January and early February 2009 led up to the ‘Black Saturday’ bushfires outside Melbourne on 7 February 2009, which became Australia’s worst natural disaster, with more than 170 people killed and 1800 homes lost. Temperature records were smashed across southeastern Australia. The tropical wet season boomed during the weak La Niña event, with Queensland and Australia as a whole recording the fifth wettest summer in the period of record (109 years)