Seasonal climate summary southern hemisphere (spring 1999): a transition toward a second successive cool episode (La Niña)

Atmospheric and oceanic conditions in the southern hemisphere are reviewed fo rhte 1999 austral spring season. Particular emphasis is given to the Australian and Pacific regions. The pattern in both the oceanic and atmospheric indicators was one of a returning La Niña phase. This transition commenced after only one season of neutral conditions, following from the previous 1998/1999 La Niña event. Most notable changes in the oceans occurred during the final month of the season, with the Pacific equatorial subsurface cooling vigorously. Likewise, rainfall and maximum and minimum temperatures over Australia displaced rapid change towards conditions commonly associated with a La Niña phase in the Pacific. In particular, November brought above normal rainfall to most of the Australian continent, as well as the lowest November all-Australian maximum temperature observed in the 1950 to the present data record. Over the Antarctic, the spring time ozone hole failed to reach the record size it achieved in 1998, however it still peaked in area at over 22 million square kilometres.