Monthly climate

Climate developments in April 2005

The SPCZ (South Pacific Convergence Zone) was noticeably more active than in March, extending from the region north of Papua New Guinea southeast towards Fiji, and across to Niue. Enhanced convection was also associated with the ITCZ (Intertropical Convergence Zone), which extended from the Caroline Islands across the Date Line and further east about 5° north of the equator. Rainfall was at least 125% of average over much of Micronesia, Vanuatu, and parts of Fiji and New Caledonia, Niue, and Tonga, some locations recording more than 300% of normal. Rainfall occurred almost every day from 6 to 20 April in Fiji’s Western Division. Extensive flooding occurred in the Northern and Western Divisions over 16-20 April, closing almost 50 roads. There were several fatalities. It was very wet in Vanuatu, Pekoa recording 950 mm for April, 5 days exceeding 100 mm.

In contrast, suppressed convection and below average rainfall occurred east of the Date Line, from Tokelau to the Marquesas Islands. Rainfall was less than 50% of average in Northern and Central French Polynesia. Another region of suppressed convection occurred over much of Australia (and Southeast Asia) across the Tasman Sea to New Zealand, where rainfall was generally well below average.

Mean air temperatures were at least 0.5 °C above average in Fiji, Samoa, and Tonga, as well as Northern and Central French Polynesia. Temperatures were at least 0.5 °C below average in parts of New Caledonia and Southern French Polynesia.

Tropical Southwest Pacific mean sea-level pressures continued above average in most areas about and west of the Date Line. They were near average over central French Polynesia, and below average in the eastern equatorial region and from Vanuatu to the Southern Cook Islands. Along the equator, surface equatorial westerlies occurred in only 1% of observations at Tarawa, reflecting a strengthening of the easterlies.

Climate extremes in April 2005