Global setting and climate outlook

Global setting and climate outlook

La Niña falters but still possible

Difference from average global SST (click to enlarge).

Monthly SOI values (click to enlarge).

Conditions in the Equatorial Pacific are currently neutral, but there is a near 50% chance of a transition to La Niña conditions during the next 2–3 months, with less than a 10% chance of El Niño conditions developing. The characteristic La Niña ‘cold tongue’ in ocean surface temperatures remains evident near the South American coast (see map below). However the SOI fell again during July to –0.4, a factor which adds uncertainty to expectations on the development of La Niña.

Sea surface temperatures(SST) around New Zealand

New Zealand SST (click to enlarge).

July SST around New Zealand were on average 0.6°C above normal. Surface conditions were warmer than normal around the North Island coast and across to the central Pacific, but cooler than normal about Cook Strait, south of Chatham Rise, and southeast of the South Island. SST are expected to remain in their current state over the next 1–3 months.

Outlook for August to October 2007

Regional outlook (click to enlarge).

During August–October, mean sea level pressures are expected to be higher to the south or southeast of New Zealand, with weaker than normal westerly winds across the country. Air temperatures are likely to be average or above average in most regions, but tending below average in the eastern South Island. Despite the overall temperature expectation, cold outbreaks typical of early spring will occur from time to time.

Normal or below normal rainfall is expected in most regions, except the north and northeast of the North Island, where normal or above normal rainfalls are likely. Normal or above normal soil moisture and river flow levels are expected in the north of the North Island; they are likely to be near normal in the east of the North Island, and normal or below normal elsewhere.