Monthly climate

Climate developments in August 2004

The SPCZ (South Pacific Convergence Zone) extended from the Solomon Islands to the region south of the Cook Islands. This included the main islands of Fiji, central and southern Tonga where rainfall was 200-400% above average. Other areas with enhanced convection and/or at least 200% of average rainfall were Pitcairn Island, the Marquesas Islands, Niue, much of Vanuatu, and the region north of, and including the Caroline and Marshall Islands north of the equator (on the rim of a large region of very enhanced convection in the northwest tropical Pacific).

Suppressed convection occurred over Southeast Asia and Papua New Guinea, and also from Tuvalu to Samoa, including Tokelau. Rainfall continued below average in parts of Queensland, Australia. Rainfall was also below average in parts of New Caledonia, northern Tonga, northern New Zealand, and central French Polynesia.

Mean air temperatures were about 1.0°C below average in parts of Vanuatu and New Caledonia, and about 1.0°C above average in Tuvalu, Samoa, and the Southern Cook Islands.

Several periods of surface westerlies occurred in the western equatorial Pacific during the month, the most sustained being from the 16th through 19th.

Tropical Southwest Pacific mean sea-level pressures remained above average over northern Australia, and continued below average east of the Date Line from the Equator to Pitcairn Island, including Fiji and Tonga.

Climate extremes in August 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 August 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.