Climate Update 68 - February 2005

February

Climate

River flows

Soil moisture

Three-month outlook

Checkpoint

Backgrounder

Backgrounder

Backgrounder
Contrasting January rainfalls and streamflows

River flow records in cubic metres per second from 1 November to early February in the Selwyn and Hurunui Rivers, Canterbury.

The maps of January rainfalls and streamflows reveal interesting contrasts. Exceptional December rainfalls over much of the country, apart from the North Island east coast and the South Island west coast, raised streamflows to high levels and elevated soil moisture conditions to well above normal.

Checkpoint

Outlook and outcome – November 2004 to January 2005
Rainfall predictions were correct for much of the North Island. There was more rain than predicted in the east of the South Island and southern Wairarapa. Parts of the South Island west coast were drier than expected.
Air temperatures were average as predicted in the southwest of the North Island, but lower than expected elsewhere.

February

Climate Update is a summary each month of New Zealand’s climate, including soil moisture and river flows.
February 2005 – Number 68
January’s climate: Cold start to January followed by welcome change to summer temperatures.
January’s river flows: High streamflows in the North Island and southern South Island followed end-of-year storms.
Soil moisture levels: Generally low rainfalls across the country, but high streamflows persisted in many areas.
Three-month outlook: Average or below average air temperatures; rainfall likely to be near or below normal in most places

Climate

New Zealand Climate
January
The first half of January was cool, but warm summer conditions dominated the last 10 days of the month. The mean temperature for January was about 3.5 °C higher than for December.
Rainfall was below average in many areas, especially eastern Bay of Plenty.

Three-month outlook

The outlook for February 2005 to April 2005
Sea surface temperatures around the country are below average at present, but are expected to recover to near average for most of the period.
Air temperatures are expected to be average or below average in all regions.
Relatively dry conditions are expected, with rainfalls likely to be normal or below normal in all districts.

River flows

River flows
High flows persisted
Streamflows were well above normal in most of the North Island apart from the Bay of Plenty, Hawke’s Bay, and Gisborne regions, and in South Canterbury, Otago and Southland outside of alpine areas .

Percentage of average January streamflows for rivers monitored in national and regional networks. The contributing catchment area above each monitoring location is shaded. NIWA field teams, regional and district councils, and hydro-power companies are thanked for providing this information.

Soil moisture

Soils drying out in many areas
Soil moisture levels in much of the country dropped dramatically from mid January, with most soils at, or less than, 50% storage at the end of the month. Southland soils remained more moist than usual for the time of year.
 
Soil moisture deficit in the pasture root zone at the end of January (right) compared with the deficit at the same time last year (centre) and the long-term end of January average (left). The analysis is done for an average soil type where the available water capacity is taken to be 150 mm.