The tropical circulation in the Australian/Asian region-November 2010 to April 2011

Abstract

A summary of the broad-scale tropical circulation from 70° E to 180° , for the six months from November 2010 to April 2011 is presented. A strong La Niña state of the El Niño Southern Oscillation (opposite of El Niño) persisted during the season with signs of weakening from February 2011. The sea surface temperature remained cooler than normal in the central and eastern equatorial Pacific during the season. The coolest waters in the equatorial Pacific remained in the central Equatorial Pacific. The Southern Oscillation Index remained strongly positive throughout the season. Onset of the Australian monsoon over northern Australia occurred around 12 December 2010, earlier than the climatological onset date and remained active until mid-March. However, monsoonal rains affected northern Australia until April and Darwin rainfall for the season was the highest on record. The Madden-Julian Oscillation signal was not clear and was erratic during the season as the convection during the season was mostly driven by a strong La Niña pattern. A total of seventeen tropical cyclones, sixteen less than average, developed in the Regional Specialised Meteorological Centre area during the period.