Global setting and climate outlook
Global setting and climate outlook
La Niña weakening
La Niña conditions have reached maturity, and are now showing signs of weakening. Below normal sea surface temperatures (SSTs) extend across most of the equatorial Pacific, with anomalies of –1.0°C or lower over the central equatorial region. The oceanic component of La Niña has weakened over the last few weeks as indicated by the weakening of the cold SST anomalies and the strengthening of a significant warm anomaly along the South American coast. The SOI weakened a little during March and was near +1.5 (down from +2.1 in February).
Sea surface temperatures(SST) around New Zealand
Sea surface temperature (SST) anomalies are positive, but weaker than last month, with the largest anomalies remaining to the west of the country. The March SST anomaly in the New Zealand ‘box’ was about +0.1 °C (down from +0.4 °C in February). Although the heat content in the Tasman Sea/New Zealand region is about normal for the time of year, there is a warm pool in the ocean layer down to about 1000 m in the mid Tasman.
Outlook for April to June 2008
Average 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 very likely to be above average in many regions. Rainfall is expected to be near normal in most places, but normal or below in the west of the North Island. Below normal soil moisture levels and stream flows are expected to continue over most of the North Island and northern South Island. Normal soil moisture levels and stream flows are expected in the west, south, and east of the South Island. Two ex-tropical cyclones 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 small chance of one more ex-tropical cyclone passing close to the country.