Climate Update 54 - December 2003

December

Climate

River flows

Soil moisture

Three-month outlook

Checkpoint

Backgrounder

Backgrounder

ENSO seasons based on Niño 3.4.

Backgrounder
Brett Mullan, NIWA
Although the mean Southern Oscillation Index (SOI) for the past three months has been below normal (–0.4), and equatorial sea surface temperatures are above average, the El Niño–Southern Oscillation (ENSO) is predicted to be in “neutral” mode over the summer.

Checkpoint

Outlook and outcome – September 2003 to November 2003
Rainfall was as predicted in the north and southwest of the North Island, but higher than normal in the east and in parts of Waikato. Canterbury was wetter than expected, while parts of the west and southwest of the South Island received near normal rain as predicted.
Spring temperatures were mostly lower than expected. River flows were higher than predicted in Canterbury and Fiordland and in most of the North Island.

December

Climate Update is a summary each month of New Zealand's climate, including soil moisture and river flows.
December 2003 – Number 54
November’s climate: November was cool and drier than usual in many places. River and stream flows were mostly normal or below normal.
November’s river flows: Low flows in parts of Northland, Marlborough, and Otago.
Soil moisture levels: Drier than average soils in much of the South Island.
Three month outlook: A little windier from the southwest. Normal or below normal temperatures.

Climate

New Zealand Climate
Mostly cool and drier than normal
November was cooler than usual over most of the North Island and in the south and west of the South Island, although sunnier than average in many South Island regions. Mean air temperatures were at least 1.5 °C below average in inland sheltered regions of King Country (-2 °C), Tongariro, Fiordland, and Otago. It was also cooler than usual in many other North Island and southern and western South Island regions.

Three-month outlook

The outlook for December 2003 to February 2004
Local circulation patterns are expected to favour below average mean sea-level pressures southeast of the country and somewhat enhanced southwesterly winds over New Zealand.
Normal or below normal rainfall is expected for the eastern South Island and northern North Island, with normal rainfalls elsewhere.

River flows

New Zealand river flows
Low flows in parts of Northland, Marlborough, and Otago
November river and stream flows were below normal or normal over much of New Zealand. Flows were above normal in Fiordland and parts of western North Island.

Soil moisture

Soil moisture
Drier than average soils in much of the South Island
Soil moisture levels reduced more quickly than normal for November in the east of the South Island and much of Otago. At the end of the month, mid Canterbury and Otago were drier than at the same time last year. Moisture levels in Northland soils were also lower than normal. Much of Taranaki was wetter than average.

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