Climate Update 74 - August 2005

August

Climate

River flows

Soil moisture

Three-month outlook

Checkpoint

Backgrounder

August

Climate Update is a summary each month of New Zealand’s climate, including soil moisture and river flows.
August 2005 – Number 74
July’s climate: Third warmest on record.
July’s river flows: River flows mostly normal.
Soil moisture levels: Low soil moisture recharge in Otago.
Three-month outlook: Mostly near or above average temperatures. Above normal rainfall likely in the east.

Backgrounder

Backgrounder
HIRDS: A tool for evaluating storm rainfalls

Screen capture of output table from HIRDS for a specifi ed location.

Estimates of high intensity rainfalls are used by scientists and engineers in a wide range of environmental studies, engineering construction work, and design flood estimation. They are also an important tool for assessing the rarity of observed rainfall amounts. Design rainfalls are used in climatological analyses by meteorologists and hydrologists, as well as in the insurance industry, to assess risks of inundation and set premiums.

Checkpoint

Outlook and outcome – May 2005 to July 2005
Rainfall was higher than predicted in parts of the north and east of the North Island and less than predicted for much of the South Island.
Air temperatures were above average as predicted in most places, apart from near normal temperatures in parts of the east of both islands and south of the South Island.
Stream flows were normal to above normal in the east of the North Island, lower than normal in the north of the South Island, and below normal to normal elsewhere.

 

The outcome maps shown here give the tercile rankings of the rainf

Climate

New Zealand climate in July 2005
The New Zealand average air temperature for July was 9.1 °C, which was about a degree higher than usual in the North Island, and up to two degrees above normal in parts of the South Island. The national temperature was the third highest since records began in the mid 1860s, after 9.6 °C in July 1998 and 9.3 °C in July 2000.

Three-month outlook

The outlook for August 2005 to October 2005
Local atmospheric circulation patterns are likely to lead to more westerly air flows than usual to the south of New Zealand, and anticyclonic conditions east of the South Island.
Air temperatures are expected to be above average in many regions, but near or above average in the east of the North Island and the north of the South Island.
Rainfalls are likely to be normal or above normal in eastern districts of both islands, and near normal elsewhere.
Soil moisture levels are expected to be normal everywhere except for the North Island east coast, wher

River flows

River flows
River flows mostly near normal
Regional river flows were normal everywhere except the southwest of the North Island, where they were normal to low. Localised wet spots were in Northland, south Canterbury and south Otago especially along the coast, and Fiordland. Central Canterbury was drier than normal.

Percentage of average July streamflows for rivers monitored in national and regional networks. The contributing catchment area above each monitoring location is shaded.

Soil moisture

Low soil moisture recharge in Otago
Normal winter recharge of soil moisture reserves has been absent so far in much of Otago and parts of South Canterbury. Soils in the rest of the country were at or near field capacity at the end of July.
 
Water balance in the pasture root zone for an average soil type where the available water capacity is taken to be 150 mm.