Seasonal climate summary southern hemisphere (summer 1998/99): a weak cold event (La Niña) in the Pacific basin

Southern Hemisphere circulation patterns for summer 1998/99 (December-February) are reviewed, with emphasis given to the tropical Pacific and the Australian region. The cold event conditions which had been developing through the winter and spring of 1998 ceased intensification during the summer, with some signs of a decline late in the summer. An enhanced Walker circulation remained in place in the western and central equatorial Pacific. Sea-surface temperatures remained cooler than normal in the central equatorial Pacific, and returned to near normal in the eastern Pacific after having been warmer than normal throughout 1998. The resultant pattern, whilst it was best described as a La Niña, differed significantly from the ‘classic’ La Niña situation. It was a notably wet summer in the northern two-thirds of Western Australia. Over much of the remainder of the country rainfall for the season was close to normal. Mean maximum temperatures were generally above average in southern Australia and below average in northern Australia, with mean minimum temperatures above average over most of the country.