Southern hemisphere circulation patterns are reviewed for winter (June – August) 1998, with particular emphasis given to the tropical Pacific Ocean and the Australian region. In autumn 1998, climate indicators suggested a decline in the strong El Niño event evident during the previous 12 months. The decline of this event continued into winter, with the climate system apparently undergoing a rapid transition toward a cool episode. Warm surface anomalies in the western Pacific Ocean were maintained throughout the season, with cool anomalies continuing to develop in central parts. However, significantly cooler than normal subsurface waters in the eastern tropical Pacific failed to penetrate the surface in the far east, so that by the end of winter weak warm anomalies remained off the coast of South America. Atmospheric indicators pointed to a dramatic resurgence of the equatorial Walker circulation in the western and central Pacific at the end of autumn 1998. Consequently the western and central Pacific displayed typical characteristics of a weak La Niña event during winter 1998, with the pattern yet to extend to the far east. Mean sea-level pressure over Australia was close to average for the season, but northwest cloudband activity resulted in a wet winter through most parts of the country. Anomalous northwesterly flow and warmer than normal waters to Australia’s north resulted in persistent warm temperatures in the northern half of the continent.
D.A. Collins (Mon,) studied this question.