Science Centres: Pacific Rim

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. The South Pacific Convergence Zone (SPCZ) extended from Nauru southeast to the region south of Niue, being further north than average west of the Date Line and further south than average east of the Date Line. Rainfall was at least 125% of normal over much of these regions, and 200% or more of normal in southeastern areas of Fiji’s main island. Rainfall was also about 200% or more of normal in parts of New Caledonia, Tonga, and the Society Islands of French Polynesia, and at least 125% of normal in the Southern Cook Islands. Rainfall was below average along the east coast of Australia, and in the Tuamotu and Marquesas Islands of French Polynesia.

Mean air temperatures were at least 1.0°C above average in Fiji, Samoa and southern Tonga, and about 0.5°C above average in the Southern Cook Islands.

During June, stronger than normal southeast tradewinds were recorded in New Caledonia and Fiji.

Periods of surface westerlies occurred in the western equatorial Pacific from 19 June onwards (into the first week of July). Tropical Southwest Pacific mean sea-level pressures were above average over Australia and the region north of New Zealand, but below average east of the Date Line from the Equator to southern French Polynesia.

Climate extremes in June 2004

Outgoing Long-wave Radiation (OLR) anomalies, in Wm-2 are represented by shaded areas, and rainfall percentage of average, shown by numbers. High radiation levels (yellow) are typically associated with clearer skies and lower rainfall, while cloudy conditions lower the OLR (blue) and typically mean higher rainfalls. The June 2004 position of the South Pacific Convergence Zone (SPCZ), as identified from total rainfall, is indicated by the solid green line. The average position of the SPCZ is identified by the dashed green line. Data source: NOAA-CIRES Climate Diagnostics Center.