Island Climate Update 45 - June 2004

Southwest Pacific Tropical Cyclones Summary for 2003/2004 Season
Stuart Burgess, NIWA
The 2003/04 tropical cyclone season had only three occurrences, being equal lowest in the last 30 years (see Figure 1). About nine tropical cyclones can normally be expected in an average season. Two of the three 2003/04 tropical cyclones reached major hurricane strength, with sustained wind speeds of at least 168 km/h.

Forecast validation
Forecast period: March to May 2004
Enhanced convection was expected in Western Kiribati, and over Wallis and Futuna, and the Society Islands, resulting in average or above rainfall there. Average or below average rainfall was expected in Pitcairn Island with suppressed convection over the Marquesas Islands where rainfall was forecast to be below average.

ENSO and Sea Surface Temperatures
Positive SOI during May
Slightly above average SST west of the Date Line
The monthly SOI rose markedly in May to +1.3 with the three month mean (March – May) close to neutral (-0.2). The oceanic and atmospheric conditions indicated a neutral phase of El Niño Southern Oscillation (ENSO) during May 2004. May SSTs were warmer than average in the western and central equatorial Pacific (NINO3 and 4 regions) and cooler than average in the eastern equatorial Pacific (NINO1 and 2 regions).

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 45 – 4 June 2004
May’s climate: South Pacific Convergence Zone inactive about and west of the Date Line. Suppressed convection and below average rainfall in many areas. Well above average rainfall in northern French Polynesia. An unusually ‘quiet’ tropical cyclone seasons.
ENSO and sea surface temperatures (SST): The May Southern Oscillation Index (SOI) was +1.3.

Climate developments in May 2004
Suppressed convection and below average rainfall predominated over a large region of the Southwest Pacific about and west of the Date Line, from Vanuatu to Samoa, including Fiji (where it was very dry and sunny in the west of the main island) and Tuvalu. Suppressed convection and below average rainfall also occurred over much of the central of southern French Polynesia across to Pitcairn Island, and along the Equator about and east of Eastern Kiribati.

Rainfall outlook for June to August 2004
Above average rainfall in Papua New Guinea and the Austral Islands
Average or below average just west and northeast of the Date Line
Enhanced convection is expected in the equatorial west Pacific over Papua New Guinea, the Solomon Islands and Western Kiribati where rainfall is likely to be average or above average.
Another region of enhanced convection, with average or above average rainfall, is expected over French Polynesia
Rainfall is expected to be average or below average over Vanuati, Fiji, Tuvalu, Tokelau, Samoa and Eastern Kiribati.

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