Monthly climate

Climate developments in September 2004

The South Pacific Convergence Zone (SPCZ) extended from Papua New Guinea south-southeast to Rotuma Island. Convergence also occurred south of Fiji east to the Southern Cook Islands, including Tonga, some areas recording at least 200% of average rainfall. The enhanced rainfall over Papua New Guinea and the Solomon Islands was caused by cross-equatorial northerlies converging with the southern hemisphere trade winds. Enhanced convection and/or at least 125% of average rainfall also occurred in the far northern and southern islands of Fiji, Niue, the northern islands of Tuvalu, the Marquesas Islands, and Pitcairn Island.

Rainfall was 50% or less of average throughout much of Vanuatu, New Caledonia, the Tuamotu, Society and Austral Islands of French Polynesia, and Pitcairn Island. Rainfall was also less than 50% of average in several Northern and Central sites in Fiji.

Mean air temperatures were near average in New Caledonia, and more than 0.5°C above average in Samoa and the Society Islands of French Polynesia. Tropical Southwest Pacific mean sea-level pressures remained above average over Australia, and continued below average east of the Date Line.

Climate extremes in September 2004

Outgoing Long-wave Radiation (OLR) anomalies, in Wm-2 are represented by shaded areas. 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 September 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.