The tropical circulation in the Australian and Asian region - May to October 2008

Abstract

A summary of the broadscale tropical circulation from 70°E to 180°, for the six months May to October 2008, is presented. During this period the neutral El Niño - Southern Oscillation (ENSO) conditions were consolidated from the previous weakening La Niña state. The Southern Oscillation Index (SOI) was positive during the season and was above one standard deviation from September. The mean SOI for the season was +6.5. Mean sea-level pressure (MSLP) anomalies for the season remained negative over the Indian Ocean and positive over much of the western Pacific Ocean. The MSLP remained higher than normal over Australia. The sea-surface temperature (SST) in the tropical Pacific was warmer in the east and the west with cooler anomalies in the central Pacific. Convection over the southern Indian Ocean and Australia was generally below average while it was close to normal or above average in the Maritime Continent and northern hemisphere monsoon region. Several active convective phases of the Madden-Julian Oscillation (MJO) were observed in the region during the season. A total of 18 tropical cyclones (including 9 typhoons) were analysed during the period, less than the mean of 30 for the Darwin Regional Specialised Meteorological Centre (RSMC) area.