Climate Update 34 - April 2002

April

Climate

River flows

Soil moisture

Three-month outlook

Checkpoint

Backgrounder

April

Climate Update is a summary each month of New Zealand's climate, including soil moisture and river flows.
April 2002 – Number 34
March’s climate: Rainfalls were low in the east of the country.
March’s river flows: High stream flows in Wellington and Buller.
Soil moisture levels: Conditions improve in the North Island.
Three month outlook: Drier than normal conditions may continue in eastern regions.
Checkpoint: How well are we doing with our predictions?
Backgrounder: Past El Niños: spring rainfall in Waikato.

This issue of the Climate Update is available as a PDF.

Backgrounder

Backgrounder
El Niño and Waikato spring climate: dry or wet?
The possibility of a return to El Niño conditions later this year has been strengthened by recent developments in the tropical Pacific (see the Climate Outlook on page 3). The best indication of the effect that El Niño might have on spring rainfall can be found in the historical record of previous El Niño springs.

Checkpoint

Outlook and outcome – January to March 2002
Rainfall was above average in Taranaki,Whanganui, and Buller as was predicted in the January to March Outlook. North and central Canterbury received more rain than was forecast. Parts of Waikato, Bay of Plenty, and East Cape were drier than expected.
Air temperatures were normal over much of the country as was expected, although large areas were cooler than forecast.

Climate

New Zealand Climate in March 2002
A dry, sunny start to autumn
March was dry, especially in the east, and sunny almost everywhere. Many eastern sites between Bay of Plenty and Otago recorded less then 50% of their usual March rainfall. Gisborne Airport recorded 12 mm and has recorded less than this only twice in 95 years. Rainfall was above average in parts of Auckland, Buller, Nelson Lakes, the Southern Alps, and coastal Southland.
Almost all New Zealand locations were sunnier than normal after a cloudy summer. It was especially sunny in Nelson and the east coast of the South Island.

Three-month outlook

The outlook for April to June 2002
There are now strong indications that an El Niño may develop by spring. One indication is that sea surface temperatures in the equatorial Pacific are now above normal, and are expected to rise further relative to normal over coming months.

River flows

New Zealand River Flows in March 2002
High stream flows in Wellington and Buller
Wellington, Wairarapa, and Buller river and stream flows were above average in March. Flows were below average in the Bay of Plenty, East Cape, Marlborough, Otago, and Southland, and near average elsewhere.

Soil moisture

Soil moisture on 31 March
Conditions improve in the North Island
Moderate soil moisture deficits continued, particularly in eastern regions, but rainfall brought some relief to Waikato and King Country. Conditions in much of the North Island were near or just below average at the end of March
Significant soil moisture deficits in Otago have now spread to parts of inland south Canterbury, central Marlborough and the Canterbury Plains.