Island Climate Update 46 - July 2004

ARGO in the South Pacific
Dr Philip Sutton, NIWA
The ocean has a remarkable capacity to transport and store heat. With 2.5m depth of water having the same heat capacity as the entire depth of the atmosphere, even small changes in ocean temperature can have large impacts on climate. Observations of the distributions of heat and freshwater (through measuring changes in salinity) are essential for understanding the oceans’ role in climate and for forecasting climate and ocean conditions.

Forecast validation
Forecast period: April to June 2004
Rainfall was expected to be above average in the Solomon Islands. Regions of enhanced convection and average or above average rainfall were also expected in Papua New Guinea and Western Kiribati, and over Tonga and Niue. Average or below average rainfall was expected over Eastern Kiribati and the Tuamotu and Society Islands, with suppressed convection over the Marquesas Islands. Near average rainfall was predicted elsewhere in the region.
A large region of enhanced convection occurred in the western equatorial region as expected.

ENSO and Sea Surface Temperatures
SOI strongly negative
SST anomalies below average near the South American coast
The tropical Pacific remains in a near neutral state with mixed warming and cooling signals and a fluctuating SOI over the past few months. June SSTs were about 0.5°C above normal in the equatorial Pacific around Western and Eastern Kiribati.
The three month SOI (April-June) continues in the neutral range, at -0.7. For June, the NINO3 SST anomaly was about +0.4°C, and NINO4 was about +0.7°C.

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 46 – 7 July 2004
June’s climate: Active convergence about and west of the Date Line. High rainfall in parts of New Caledonia, Fiji, Tonga and central French Polynesia.

Climate developments in June 2004
Enhanced convection and above average rainfall occurred over much of the tropical Western Pacific extending southeast towards the Date Line, affecting eastern parts of Papua New Guinea, the Solomon Islands, the Caroline Islands, Nauru, Western Kiribati, Tuvalu, and areas in Fiji. This was in contrast to suppressed convection about and west of the Date Line in the Southwest Pacific during May.

Rainfall outlook for July to September 2004
Above average rainfall over the Austral Islands
Suppressed convection over Vanuatu, New Caledonia and Fiji
Variability in the ENSO system, and the present lack of coherent large-scale forcing of the tropical Pacific climate system mean that global model seasonal rainfall guidance is quite inconsistent for most Pacific Island countries.

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