Climate Update 39 - September 2002

Backgrounder

2002 rainfall to date
Large areas of New Zealand have received near normal rainfall. Parts of Waikato, Bay of Plenty, and the northeast and southwest of the South Island have been drier than average.

Total rainfalls for 1 January to 31 August 2002.
Update on the SOI
The mean Southern Oscillation Index (SOI) for August was -1.8, with the three month average now at -1.1. The present moderate El Niño is expected to be weaker than the 1997-98 event. Further general information on El Niño is available on the World Meteorological Organization web site.

New Zealand Climate
Mild conditions widespread
Despite a cold, wintry outburst during the last week, August was warmer than usual, especially in the South Island.

New Zealand River Flows
August streamflows varied
August flows were below normal for most of the country, but above normal around Gisborne and Hawke’s Bay, and in parts of inland Otago and the South Island hydro lakes.

Soil moisture on 31 August
Pockets of drier than normal soils were evident at the end of August in Bay of Plenty, Hawke’s Bay, Marlborough, Canterbury, and in inland and coastal Otago. Rainfall was below average for both July and August in northern and central areas of the South Island, resulting in lower than normal subsoil moisture content in Marlborough and mid and south Canterbury.

Soil moisture deficit in the pasture root zone at the end of August (right) compared with the deficit at the same time last year (centre) and the long term end of August average (left).