Global setting and climate outlook
Global setting and climate outlook
La Niña likely to remain until autumn
Difference from average global SST (click to enlarge).
Monthly SOI values (click to enlarge).
A mature La Niña event continues in the tropical Pacific, and is very likely to persist through autumn 2008. Below normal sea surface temperatures (SSTs) extend across most of the equatorial Pacific, with anomalies of –2.0 °C or more over the central equatorial region (Date Line to 120° W, approximately). The warm ‘horseshoe’ SST pattern (see map) is in evidence in the extra-tropics of both hemispheres and is less patchy than in previous months.
Sea surface temperatures(SST) around New Zealand
New Zealand SST (click to enlarge).
Sea surface temperature anomalies (departures from normal) in the New Zealand region are positive, which is consistent with a La Niña event, although the largest anomalies remain to the west of the country. The February SST anomaly in the New Zealand box was about +0.4 °C. Sea surface temperatures around New Zealand are expected to remain above normal during autumn.
Outlook for March to May 2008
Regional outlook (click to enlarge).
Autumn mean sea level pressures are expected to be higher than normal east of the South Island and lower than normal to the north of New Zealand, with weaker than normal westerlies over the country.
Air temperatures are likely to be average or above average across the country. Rainfall is expected to be near normal in most places, but may be above normal in Northland. Normal or below normal soil moisture and river flows are likely in the southwest North Island and the west, south, and east of the South Island. Elsewhere, normal conditions are expected. Two ex-tropical cyclones have passed close to New Zealand during the current tropical cyclone season. For the remainder of the season (through to May 2008), there is still a chance of at least one more ex-tropical cyclone passing close to the country. The regions most at risk are the north and northeast of the North Island.