Island Climate Update 23 - August 2002

Correlation between the annual Southern Oscillation Index (SOI) and annual mean SLP, surface temperature and percentage of normal precipitation, for the most recent negative and positive phase of the IPO.
(Click to enlarge)
Part 2 – Interdecadal Pacific Oscillation – Modulating ENSO
A Gosai, B Mullan, J Renwick and J Salinger
The Interdecadal Pacific Oscillation (IPO) modulates teleconnections with ENSO in a complex way, strengthening relationships in some areas and weakening them in others.
Although the IPO and ENSO operate on different time scales, they are similar in their

Forecast validation
Forecast period: May to July 2002
Rainfall was projected to be above average in Western and Eastern Kiribati, as well as Tonga, and average or above average in Vanuatu and in southern and central French Polynesia. Below average rainfall was projected from the Northern Cook Islands to the Marquesas. Average rainfall was forecast for other areas.
Rainfall was higher than expected in Samoa and the Marquesas Islands, and lower than expected in New Caledonia, Tonga, Kiribati, the Southern Cook Islands, and the Society Islands.

ENSO and Sea Surface Temperatures
Warm seas persist throughout much of the Pacific
The chance of an El Niño remains high
In the equatorial Pacific, a band of anomalously warm water persists about the dateline (at least 1.5°C above average).Although much of the Southwest Pacific remain about 0.5°C–1.0°C above average, there is cooling in the Coral Sea particularly north of New Zealand and around New Caledonia.

Enhanced convection from the Solomon Islands southeast to Niue
Below average rainfall from Australia to New Caledonia and from Eastern Kiribati to the Cook and Society Islands
The SPCZ moved further south in July, to extend east from the Solomon Islands through southern Tuvalu to the north of Samoa, being displaced south of its mean position. It continued to be weak with little activity further east in the southwest Pacific.

Rainfall outlook for August to October 2002
Above average rainfall in equatorial latitudes from west to east
Average or above average rainfall in Tuvalu, the Society Islands and Pitcairn
Average or below average rainfall in Papua New Guinea, New Caledonia, Samoa, Cook Islands, and the Marquesas Islands
Mainly average rainfall in other areas
The El Niño is expected to have an influence on the rainfall in some areas, particularly along the equator and in the Coral Sea.
The South Pacific Convergence Zone is expected to remain fairy inactive east of the date line, with average or below ave

Sources of South Pacific rainfall data
This bulletin is a multi-national project with important collaboration from the following Pacific nations:
American Samoa
Australia
Cook Islands
Fiji
French Polynesia
Kiribati
New Caledonia
New Zealand
Niue
Papua New Guinea
Pitcairn Island
Samoa
Solomon Islands
Tokelau
Tonga
Tuvalu
Vanuatu
Requests for Pacific island climate data should be directed to the Meteorological Services concerned.
Acknowledgements
This bulletin is made possible with financial support from the New Zealand Agency for International Development (NZAID), Wellington, New Zealand, wi