Seasonal climate summary southern hemisphere (winter 2009): a developing El Nino and an exceptionally warm winter for much of Australia

Southern hemisphere circulation patterns and associated anomalies for the austral winter 2009 are reviewed, with emphasis given to the Pacific Basin climate indices and Australian rainfall and temperature patterns. Sea-surface temperatures remained significantly higher than the long-term average across most of the tropical Pacific Ocean in winter, exceeding El Nino thresholds from west of the date-line to the South American coast. Subsurface waters cooled through July and August, but a large volume of the subsurface still remained significantly warmer than the long-term average. The SOI was near-neutral for the season, not indicating an El Nino state. Trade winds were generally weaker than normal across the tropical Pacific. Although cloudiness near the date-line increased, it did not show a strong trend towards El Nino-like values. The season was exceptionally warm over much of Australia. Average maximum temperatures over the country were the highest on record, while seasonal mean temperatures fell only just short of the 1996 record. It was also a rather dry season over much of the continent, particularly the north and east.