Are heavy rainfalls becoming more frequent?
At least 13 high rainfall events have occurred in New Zealand over the past 12 months, in some cases resulting in severe floods.
Climate Update 63 - September 2004
Outlook and outcome – June 2004 to August 2004
Many districts recorded average rainfall, as predicted, and it was drier than normal in Northland and Auckland. Parts of the east and south of the North Island, and the northwest and south of the South Island, were wetter than expected.
Air temperatures were average, as predicted, in many areas, and average or below average, as predicted, in the southern South Island. It was cooler than predicted in the northwest of the South Island and in the Auckland region.
New Zealand Climate
Coldest August since 1992
The average New Zealand temperature was 7.9 °C, the lowest August average temperature for more than 10 years. Much of the country was more than 0.5 °C cooler than average, and temperatures in parts of coastal Wairarapa and the South Island were more than 1.5 °C below average.
The low temperatures were associated with wet conditions in some areas. About 200% of normal rainfall fell in parts of Wairarapa, Canterbury, Otago, and coastal Southland.
The outlook for September 2004 to November 2004
Lower than normal mean sea-level pressures in the south Tasman Sea are expected during spring, with more west to southwest wind flow than usual over New Zealand. Surface temperatures of seas close to the country are expected to be near average.
Temperatures are expected to be near average in most regions, but above average in the eastern North Island and northern South Island. Normal or below normal rainfall is expected in the north and east of the North Island, with normal or above normal rain in the west and south of the South Island.
High river flows follow heavy rain
Stream and river flows were above normal in the central and southern North Island, Buller, and coastal Southland. Flows were below normal in Northland and Auckland, and normal elsewhere.
Climate Update is a summary each month of New Zealand’s climate, including soil moisture and river flows.
September 2004 – Number 63
August’s climate: Temperatures at 10 year low. Very wet in Wairarapa, Canterbury, Otago, and coastal Southland.
August’s river flows: High river flows in the central and southern North Island, Buller, and coastal Southland.
Soil moisture levels: Marlborough-Kaikoura coast and parts of inland Otago lower than average.
Three-month outlook: Below normal rain likely in the north and east North Island.
South Island dry spots
Soil moisture levels along the Marlborough-Kaikoura coast and in parts of inland Otago were lower than average at the end of August. Bay of Plenty and central North Island soils were also a little drier than normal. Soils elsewhere were near field capacity.
Soil moisture deficit in the pasture root zone at the end of August (right) compared with the deficit at the same time last year (centre) and the long-term end of August average (left). The analysis is done for an average soil type where the available water capacity is taken to be 150 mm.