La Niña intensifies; warm late spring period very likely

NIWA has just issued its seasonal climate outlook, covering conditions expected (on average) for the next three months as a whole.

The current La Niña has recently strengthened. A moderate to strong La Niña event is presently underway, with further intensification possible this year. La Niña conditions are likely to continue through to at least autumn of 2011.

Late spring (October¬–December) temperatures are likely to be above average, in all regions. Rainfall is likely to be near normal or below normal in the east of both islands and the southwest of the South Island, and near normal elsewhere, averaged over the three month period October–December.

Soil moisture levels and stream flows are likely to be near normal or below normal in most regions, except the southwest of the North Island and northern South Island where near normal levels are likely.

The National Climate Centre’s seasonal outlook states that mean sea level pressures are likely to be above normal over and south of New Zealand, for October–December as a whole, with weaker than normal westerly winds.

Overall Picture

Temperature:

Temperatures are likely to be above average in the east of both islands and in the north of the South Island, and very likely to be above average in other districts. Sea surface temperatures are presently near normal around New Zealand, but are expected to become warmer than normal around the North Island as the season progresses.

Rainfall, soil moisture, and stream flows:

Seasonal rainfall is likely to be near normal or below normal in the east of both islands and the southwest of the South Island, and near normal elsewhere. Soil moisture levels and stream flows are likely to be near normal or below normal in most regions, except in the southwest of the North Island and north of the South Island, where they are likely to be near normal.