Island Climate Update 32 - May 2003

23 March 2007 - 2:19pm

Science Centres: Climate

May

Monthly climate

ENSO & SST

Forecast validation

Three-month outlook

Feature article

Data sources

Feature article
Tropical Cyclone summary for the 2002/03 season Stuart Burgess and Ashmita Gosai, NIWA ‘Fili’, was the only tropical cyclone to occur in April, bringing gale force winds to parts of Tonga on the 14th. This was the ninth tropical cyclone to occur so far this season, the same as that of an average season (9), and three more than during the previous season (6). January 2003 was the most active month, with 3 occurrences. The 2002/03 tropical cyclone season was the most active since the season of 1998/99 when there were also 9 occurrences (see Figure 1).

Forecast validation
Forecast validation Forecast period: February to April 2003 Enhanced convection over Western and Eastern Kiribati was expected to persist, extending west to include the Solomon Islands. Above average or average rainfall was also expected from Tuvalu across to the Society Islands of central French Polynesia. Below average rainfall was predicted for New Caledonia, the Marquesas Islands and Pitcairn Island. Average or below average rainfall was expected in many areas from Vanuatu east to the Austral Islands, including Fiji and Tonga.

ENSO & SST
ENSO and Sea Surface Temperatures Neutral conditions prevail in the tropical Pacific Negative SST anomalies have developed along the South American coast The El Niño event in the tropical Pacific has ended as most El Niño Southern Oscillation (ENSO) indicators return to neutral conditions. The NINO3 SST anomaly was zero in April, and NINO4 has eased back to +0.6°C. The three month (February – April) means are about +0.3°C and +0.9°C for NINO3 and NINO4, respectively.

May
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 32 – 8 May 2003 April’s climate: The El Niño episode is now over, with enhanced equatorial easterlies across the Pacific. The South Pacific Convergence Zone (SPCZ) was displaced further north than average, with enhanced convection and above average rainfall in many areas from Tuvalu to the Society Islands of French Polynesia.

Monthly climate
Climate developments in April 2003 SPCZ further north, from Tuvalu to the Society Islands Enhanced convection no longer exists over Kiribati The SPCZ was displaced further north than average, with enhanced convection over parts of Tuvalu, Tokelau, and the Society Islands of French Polynesia. April rainfall was at least 125% of average (and 300 mm or more in places) over much of this region.

Three-month outlook
Rainfall outlook for May to July 2003 Average or above average rainfall is expected in many equatorial regions Average or below average rainfall in Fiji, Tonga, Niue, and the Tuamotu Islands Below average rainfall in the Marquesas Islands The enhanced equatorial convection that was prevalent over last year has now dissipated with the strengthening of the easterly tradewinds across the equatorial Pacific. Average or above average rainfall is the most likely outcome for Western and Eastern Kiribati, the Solomon Islands, Tuvalu, Tokelau and the Society Islands.

Data sources
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