Global setting and climate outlook

Global setting and climate outlook

La Niña weakening

Difference from average global SST (click to enlarge).

La Niña is now weakening in the tropical Pacific, and is expected to ease to neutral conditions by July. At the ocean surface, temperature anomalies have eased dramatically across much of the equatorial Pacific. By the end of April, sea surface temperature anomalies were positive near the South American coast. The SOI eased further in April to about +0.5, with a three month average of +1.2.

Sea surface  temperatures(SST) around New Zealand

New Zealand SST (click to enlarge).

Sea surface temperature (SST) anomalies have risen in the New Zealand region in April, as the ‘warm horseshoe’ associated with La Niña has consolidated in the southern extra-tropics. The April SST anomaly in the New Zealand ‘box’ was about +0.9 °C, having risen from +0.1 °C in March. Sea surface temperatures around New Zealand are expected to remain above normal during the next three months.

Outlook for May to July 2008

Regional outlook (click to enlarge).

Average atmospheric pressures are expected to be higher than normal to the south of the South Island and lower than normal to the northwest of New Zealand, with more winds from the northeast than normal over the country.

Air temperatures are very likely to be above average in many regions. Despite this overall temperature expectation, cold outbreaks typical of late autumn and winter will occur from time to time. Rainfall is expected to be normal or above normal in the north and east of the North Island, normal or below in the southwest South Island, and near normal elsewhere. Soil moisture levels and stream flows are likely to be above normal in the northern North Island, near normal in the eastern North Island and northern South Island, and normal or below normal in the southwest of the North Island and the west, south, and east of the South Island.