Climate Update 46 - April 2003

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 2003 – Number 46
March’s climate: New Zealand’s climate during March was dominated by anticyclonic conditions, bringing unusually dry and sunny weather to many areas.
March’s river flows: March flows mostly low.
Soil moisture levels: Patchy relief for dry soils with significant soil moisture deficits continuing in some regions.
Three month outlook: Near normal rainfall: with El Niño’s departure the risk of ongoing dry conditions in the east is n

Backgrounder

Backgrounder

ENSO signal approaching neutral
The current warm phase of the El Niño-Southern Oscillation is nearing its end and is not expected to influence New Zealand’s climate over the next few months.
Most forecast models of the development of the El Niño–Southern Oscillation are predicting neutral conditions through late autumn and winter.

Mean sea surface temperature departures from normal.
Update on the SOI
The mean Southern Oscillation Index (SOI) for March was –1.0, with the three month average now at –0.7.

Checkpoint

Outlook and outcome – January 2003 to March 2003
Rainfall was as predicted for parts of Waikato, Bay of Plenty, the east of the North Island, Marlborough and Nelson, and eastern Otago. Rainfall was lower than forecast in western regions, and higher than forecast in the north of the country.
Air temperatures were average in most regions, as expected.
River flows were higher than expected in Northland, Waikato, and in parts of the east of the North Island.

Climate

New Zealand Climate
Settled, dry and sunny
New Zealand’s climate during March was dominated by anticyclonic conditions, bringing unusually dry and sunny weather to most areas apart from the north of the country. For many localities it was a continuation of already unusually dry summer conditions.
Lower than usual pressures to the north of the country strengthened northeasterly air flow over New Zealand with resulting high rainfalls in North Auckland, Auckland, Coromandel, and Gisborne.

Three-month outlook

The outlook for April to June 2003
For April–June, temperatures are expected to be average over the North Island and north of the South Island, and average or below average over the rest of the South Island.
Normal or below normal rainfall is expected in the east of both main islands, with near normal rainfall likely elsewhere.
Soil moisture levels and river flows are predicted to be below normal in eastern regions of both islands, and to be normal or below normal elsewhere.
The El Niño event in the tropical Pacific is nearing its end, and little influence from this is expected on N

River flows

New Zealand River Flows
March flows mostly low
March streamflows were high in parts of Northland, Coromandel, and the East Cape, but below normal elsewhere.

Soil moisture

Soil moisture
Patchy relief for dry soils
Significant soil moisture deficits continued through much of March in the north and east of the South Island, from Nelson to Otago, as well as in the southwest North Island from Wanganui to Wellington, and in Wairarapa.