Climate Update 35 - May 2002

May

Climate

River flows

Soil moisture

Three-month outlook

Checkpoint

Backgrounder

Backgrounder

Backgrounder

2002 rainfall to date
Rainfall so far this year has been lower than average in much of the north of the North Island and in parts of the north and west of the South Island. Eastern areas of the South Island have been wetter than average.

Total rainfalls for 1 January to 7 May 2002, shown according to decile rankings of all rainfalls for this period from 1972.
Update on the SOI
The Southern Oscillation Index (SOI) for April was -0.5, with the three month average at about -0.2.

Checkpoint

Outlook and outcome – February to April 2002
Rainfall was below average, as forecast, in the northern North Island, Gisborne and eastern Marlborough. It was lower than expected in inland South Canterbury and Central Otago, and higher than expected in Southland.
Air temperatures were expected to be normal or above normal in all districts. This was correct for much of the country, but eastern regions from Bay of Plenty to Canterbury were cooler than predicted.
River flows were near normal, as expected, in the east of both islands.

May

Climate Update is a summary each month of New Zealand's climate, including soil moisture and river flows.
May 2002 – Number 35
April’s climate: Some very dry condtions in the east of the country were alleviated by April rains.
April’s river flows: Mostly below normal streamflows in April.
Soil moisture levels: End of month rainfalls relieve dry soils.
Three month outlook: Normal or above normal temperatures are expected over much of the country for the next three months.
Checkpoint: How well are we doing with our predictions?
Backgrounder: Past El Niños: spring rainf

Climate

New Zealand Climate in April 2002
East-west divide in the south
Below average rainfall with above normal temperatures and abundant sunshine occurred in the west of the South Island, while the east of the island recorded above average rainfall and cooler than normal conditions.
Over much of the remainder of the South Island temperatures were near normal.

Three-month outlook

The outlook for May to July 2002
It is still possible that a developing El Niño event may influence New Zealand climate by spring 2002, but it is not expected to affect New Zealand climate over the coming winter. Conditions in the tropical Pacific that indicate how El Niño is developing have changed little between March and April.

River flows

New Zealand River Flows in April 2002
Mostly below normal streamflows in April
April flows were below normal in most places. Nearer normal flows occurred in Bay of Plenty, some parts of Northland, the South Island east coast, and Southland.

Soil moisture

Soil moisture on 30 April
End of month rainfalls relieve dry soils
The very dry soil conditions that developed in eastern and some inland regions during early April were alleviated by some timely rainfall late in the month. Notable were significant rainfalls along the east coast of the South Island from Kaikoura to south Otago. Falls of over 60 mm were also recorded in some locations in inland Otago.
In the southern half of the North Island, and across most of the South Island, soil moisture levels were higher at the end of April than at the same time last year.