June

An overview of the present climate in the tropical South Pacific Islands, with an outlook for the coming months, to assist in dissemination of climate information in the Pacific region.

Number 21 – 11 June 2002

May’s Climate: The South Pacific Convergence Zone (SPCZ) was further south than average west of the date line, but further north than usual over much of the region to the east. Areas of enhanced convection and average to above average rainfall affected the region south of the Solomon Islands across Vanuatu to Fiji, with another band of enhanced convection extending from the east of the Tokelaus across the Northern Cook Islands through the Tuamotu Islands to Pitcairn Island. Sunny conditions prevailed about and east of Kiribati, with below average rainfall in the Southern Cooks Islands and the Society Islands of French Polynesia, as well as the Queensland coast of Australia and the western Coral Sea. Willis Island has now recorded 10 consecutive months with below average rainfall. Unusually high mean May air temperatures persisted in parts of Fiji. A weak tropical cyclone ‘Upia’, affected the sea area between Papua New Guinea and the Solomon Islands from 25 to 28 May.

ENSO and sea surface temperatures (SST): In May, a widespread weakening of the tradewinds coupled with a rapidly falling Southern Oscillation Index (SOI) and warming of the equatorial Pacific sea surface has increased the chance of an El Niño to at least 70%. Currently, sea surface temperatures in central equatorial Pacific are about 1°C warmer than normal. Notably, this is the first month since the 1997/98 El Niño when the SOI has fallen so low.

Forecast validation: How well are we doing with our predictions?

Three month outlook: Above average rainfall is likely in equatorial latitudes from west to east, with a tendency towards below average rainfall in Papua New Guinea, New Caledonia, Fiji, Samoa and the Marquesas and Austral Islands; mainly average rainfall in other areas.

Feature Article: The Interdecal Pacific Oscillation – Pacific Climate Shifts.

Sources of South Pacific rainfall data

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