Climate Update 59 - May 2004

May

Climate

River flows

Soil moisture

Three-month outlook

Checkpoint

Backgrounder

Backgrounder

Backgrounder
The state of hydroelectric power storage

The total potential electrical generation stored in hydro lakes in New Zealand. (Graph by courtesy of M-co, The Marketplace Company.)

New Zealand’s electricity usage rises with the onset of winter. This rise in use matches the winter increase of inflows to hydroelectric power stations in the North Island. In contrast, in the South Island, there is a mismatch.

Checkpoint

Outlook and outcome – February 2004 to April 2004
Mean atmospheric pressure was below average to the south of New Zealand as predicted, but wind patterns were more southwesterly than expected, bringing lower than average air temperatures over the country.
Rainfall was well predicted in most places.
Although April was a dry month over much of the country, a sequence of severe February floods gave exceptionally high February-April streamflows for most of the North Island apart from the Bay of Plenty, East Cape, and northern Hawke’s Bay regions, where normal or above normal flows occu

May

Climate Update is a summary each month of New Zealand's climate, including soil moisture and river flows.
May 2004 – Number 59
April’s climate: a second consecutive month of generally drier conditions, low temperatures, low stream flows in many places.
April’s river flows: Low stream flows widespread.
Soil moisture levels: Dry spots linger.
Three-month outlook: average to lower than average air temperatures.

Climate

New Zealand Climate
Dry and cool
April continued the generally cold dry theme of March. Rainfall was well below average over much of the northern half of the North Island until almost the end of the month. Less than 50% of average April rain fell in Northland, Auckland, much of Waikato, the central North Island Plateau, Westland, Fiordland, south Canterbury, and the Southern Lakes district.

Three-month outlook

The outlook for May 2004 to July 2004
Above average mean sea level pressures are expected to the north of New Zealand with a tendency towards more cool westerly winds than usual.
Local sea surface temperatures are likely to remain below average around New Zealand over the coming three months. Air temperatures are expected to be below average or average in all regions.
Rainfalls are expected to be near normal in the North Island and northern South Island, normal or above normal in the western South Island, and normal or below normal in the eastern South Island.

River flows

Low stream flows widespread
Despite low April rainfalls in the Waikato and central North Island, stream flows in that area were still receding from very high rates at the end of February and were near normal. Stream flows were also near normal in the western North Island, above normal in South Otago and eastern Southland, and below normal in most other areas.

Soil moisture

Dry spots linger
Soil moisture levels in eastern regions of the South Island, in North and Central Otago, and in parts of the north and east of the North Island remained lower than normal at the end of April. Southland soils, and western parts of the North Island, were wetter than at the same time last year.
 
Soil moisture deficit in the pasture root zone at the end of April (right) compared with the deficit at the same time last year (centre) and the long-term end of April average (left).