Island Climate Update 43 - April 2004

Ocean signals after the 1997–98 El Niño
Dr Melissa Bowen and Dr Phil Sutton, NIWA
A series of warm events occurred in the Southwestern Pacific after the unusually strong 1997-98 El Niño. In 1998, record sea surface temperatures were measured around New Zealand, coral bleaching took place on the Great Barrier Reef, and a warming trend in the Tasman Sea increased. At the beginning of 1998, a region of elevated sea surface temperature formed, stretching southwest from the Queensland coast past New Zealand (Fig. 1). These elevated temperatures persisted for most of 1998.

Forecast validation
Forecast period: January to March 2004
Enhanced convection with above average or average rainfall was expected in parts of the tropical Southwest Pacific from the Solomon Islands extending east to the Austral Islands, including Samoa, the Northern Cook Islands and the Society and Austral Islands. Below average rainfall was predicted for the Marquesas Islands.

ENSO and Sea Surface Temperatures
SOI near zero
Equatorial SST anomalies are near zero
The equatorial Pacific is in a neutral state. Equatorial SST anomalies are near zero, but continue slightly positive in the far west.
The monthly and seasonal SOI values are near zero. The NINO3 SST anomaly for March was about +0.2°C and NINO4 about +0.3°C (January to March are +0.3°C and +0.6°C, respectively). A Madden-Julian Oscillation (MJO) event induced westerly wind anomalies in the western Pacific from mid-March but the trade winds are otherwise near normal.

Climate developments in March 2004
In March a large region of enhanced convergence persisted over the Caroline Islands, Papua New Guinea, northern Australia, and the Solomon Islands, extending into the Coral Sea (with rainfall exceeding 400 mm at many locations).

Rainfall outlook for April to June 2004
Above average rainfall over the Solomon Islands
Suppressed convection in the equatorial eastern Pacific – Eastern Kiribati, the Marquesas Islands and parts of central French Polynesia
Enhanced convection is expected with above average rainfall over the Solomon Islands and average or above average rainfall in Papua New Guinea and Western Kiribati. Another smaller region of enhanced convection is expected near the Date Line resulting in average or above average rainfall in Tonga and Niue.

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