Monthly climate

Climate developments in May 2005

The South Pacific Convergence Zone (SPCZ) was further north and east than usual in May, extending from the region north of Tuvalu over the Northern Cook Islands and southeast through central French Polynesia. Enhanced convection occurred over much of the Solomon Islands, Vanuatu, and New Caledonia, and also central French Polynesia. May rainfall was about 300% of normal in parts of New Caledonia and central French Polynesia, and at least 125% of normal over much of Tuvalu. Other areas of enhanced convection were associated with the Intertropical Convergence Zone (ITCZ), which extended from near the Caroline Islands across the Date Line and further east, north of the equator.

Suppressed convection and below average rainfall occurred about and east of the Date Line, from Fiji to Samoa and southeast to Southern French Polynesia. Rainfall was well below average in parts of Fiji and northern Tonga, some locations recording less than 5 mm for the whole month. Convection was also suppressed over northern and eastern Australia.

Mean air temperatures were more than 1.0 °C above average in Western Kiribati, and at least 0.5 °C above average in Tuvalu, Tonga, Fiji, and Vanuatu. In contrast, they were more than 1.0 °C below average in Southern French Polynesia, and about 0.5 °C below average in the Southern Cook Islands.

Tropical Southwest Pacific mean sea-level pressures continued above average in many areas well west of the Date Line. They were below average along the equator east of the Date Line, and over central and northern French Polynesia.

Along the equator, surface equatorial westerlies occurred in 19% of observations at Tarawa, reflecting a weakening of the easterlies.

Correction: May issue of ICU mentioned “several fatalities in Fiji”, which was not correct. There was only one fatality.

Climate extremes in May 2005