Monthly climate

Climate developments in October 2004

The SPCZ (South Pacific Convergence Zone) was very active over the Solomon Islands, extending east-southeast to Rotuma Island, and across to the region north of Samoa. The enhanced rainfall over the Solomon Islands was caused by a continuation of by cross-equatorial northwesterlies converging with the southern hemisphere trade winds. Enhanced convergence also occurred over Vanuatu. Rainfall was at least 200% of average in isolated parts of Vanuatu, and also the Loyalty Islands of New Caledonia, and at least 125% of average rainfall occurred in parts of Vanua Levu (the northern island of Fiji), Samoa, and the Marquesas Islands of French Polynesia. A high rainfall event in the Loyalty Islands on the 20th produced 150 – 300 mm.

A large region of suppressed convection occurred over Southeast Asia, Indonesia, and northern Australia, extending to southern Papua New Guinea and the Caroline Islands. Convection was also suppressed over Western Kiribati, and much of Tuvalu. Rainfall was well below average, being less than 25% of average in parts of New Caledonia’s main island, and less than 50% of average in the main island of Fiji and in southern Tonga, where ridges of high pressure were frequent.

Mean air temperatures were at least 0.5 to 0.9°C above average in Western Kiribati, Samoa, southern Tonga, the Southern Cook Islands, and the Society Islands of French Polynesia, consistent with the warm sea surface temperatures affecting these regions. Tropical Southwest Pacific mean sea-level pressures were at least 1 hPa above average in the region from New Caledonia east to the southern Cook Islands.

Climate extremes in October 2004