Island Climate Update 30 - March 2003

The Southwest Pacific Climate in 2002
By Stuart Burgess, Ashmita Gosai, and Dr Jim Salinger, NIWA
The year 2002 was one of more contrasts across the Southwest Pacific. Important drivers of the annual pattern were the development of the El Niño conditions during the second half of the year (See Fig.1), the decreased strength of the trade winds, and the distribution of warm sea surface temperature (SST) anomalies.
Anomalous equatorial westerlies occurred about and west of the Dateline and in the central Pacific from July through November.

Forecast validation
Forecast period: December 2002 to February 2003
The El Niño related region of enhanced convection over Western and Eastern Kiribati was expected to persist. Above average or average rainfall was also expected in Tuvalu and Tokelau. A tendency towards below average rainfall was forecast for a broad region from the Solomon Islands southeast to the Southern Cook Islands, including Vanuatu, New Caledonia, Fiji, Tonga, and Niue, as well as the Marquesas Islands.

ENSO and Sea Surface Temperatures
El Niño easing to neutral state
Equatorial Pacific SSTs weaken further during February
Based on the oceanic and atmospheric observations, the El Niño event is now easing back towards a neutral state. Most leading El Niño Southern Oscillation (ENSO) models indicate that the event will weaken to neutral state by end of May 2003.
The NINO3 SST anomaly dropped 0.5°C in February (now +0.5°C), and NINO4 dropped to +1.0°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 30 – 6 March 2003
February’s climate: The El Niño episode although weakening continued to affect Southwest Pacific rainfall patterns, with enhanced convection and above average rainfall extending from Western Kiribati through Tokelau to the Northern Cook Islands. In contrast, a large area of suppressed convection and below average rainfall extended from Papua New-Guinea to Niue.

Climate developments in February 2003
SPCZ produces enhanced convection from Western Kiribati to Pitcairn
Suppressed convection from Papua New-Guinea to Niue
The SPCZ was generally displaced further north and east than average, with enhanced convection over much of the region from Western Kiribati southeast to Pitcairn Island. An equally large area of enhanced convection also occurred further west, over Indonesia and much of Australia.

Rainfall outlook for March to May 2003
Above average rainfall in Western and Eastern Kiribati, average or above average rainfall expected in Tuvalu
Average or below average rainfall from New Caledonia east to Niue and parts of French Polynesia
Below average rainfall in the Marquesas Islands
Enhanced convection is expected to continue over Western and Eastern Kiribati resulting in above average rainfall.

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