A summary of the broadscale tropical circulation from 70°E to 180°, for the six months May to October 2002, is presented. Starting from the neutral conditions at the beginning of the period, a weak to moderate El Niño evolved through the season. El Niño conditions were endorsed by positive pressure anomalies over most of the equatorial latitude belt, negative values of the Southern Oscillation Index, warm sea-surface temperature anomalies in the northwestern Pacific and westerly wind anomalies at lower levels in the equatorial Pacific close to the dateline supported by an eastward shift in the weather patterns. Though a few major active convective events occurred during the season, only three could be attributed to the 30 to 60-day intraseasonal oscillation with periodicity around 35 days at the beginning and end of the season; with a gap of 50 to 60 days in the middle. However, several convective periods enhanced by the passage of waves such as equatorial Rossby waves and gravity waves made it difficult to estimate the Madden-Julian Oscillation (MJO) west to east propagation and the periodicity accurately. A total of 23 tropical cyclones (10 typhoons) developed during the period, less than the mean (26) for the RSMC area, which is consistent with the moderate El Niño conditions.
Shaik et al. (Mon,) studied this question.
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