Climate Update 58 - April 2004

April

Climate

River flows

Soil moisture

Three-month outlook

Checkpoint

Backgrounder

April

Climate Update is a summary each month of New Zealand's climate, including soil moisture and river flows.
April 2004 – Number 58
March’s climate: Record low rainfall in parts of the north; temperatures well below average.
March’s river flows: High March streamflows in the North Island caused by February storms.
Soil moisture levels: Moisture levels drop due to low rainfall.
Three-month outlook: Cool and at times frosty conditions expected.

Backgrounder

Backgrounder

What is the UV (ultraviolet radiation) index?
The UV index is a standard measurement of erythemal (sunburn-causing) UV intensity that gives a more objective measure than the old “time to burn” (which cannot account for skin tone).
The UV index scale is open ended, but the larger the number, the more intense the UV. A UV index of greater than 10 is extreme and a UV index of less than 1 is low.
In New Zealand, its maximum summer value is generally about 12, but it can exceed 13 in the far north.

Climate

New Zealand Climate
Low rainfalls, low temperatures
March rainfall, in a dramatic contrast to the extremely wet February, was well below normal throughout much of the North Island and northern South Island, with many locations recording less than 50% of average totals.

Three-month outlook

The outlook for April 2004 to June 2004
A tendency towards more south or southwesterly winds is likely. Sea surface temperatures close to New Zealand are expected to remain lower than normal.
Air temperatures are expected to be below average in the South Island and average or below average in the North Island.

River flows

February rainfalls lift March flows
High March streamflows over much of the North Island were a consequence of the severe storms in mid and late February. Streamflows in the west and south of the South Island were normal or above normal. Streamflows in the north and east of the South Island tended to be below normal.
 

Soil moisture

Moisture levels drop due to low rainfall
Unusually low rainfall in the north of the country resulted in low soil moisture levels by the end of March. Northland, Auckland, Waikato, Bay of Plenty, and Hawke’s Bay soils were drier than average, while Manawatu soils also had little moisture replenishment during the month. Soils on much of the South Island’s east coast were drier than normal.
 
Soil moisture deficit in the pasture root zone at the end of March (right) compared with the deficit at the same time last year (centre) and the long-term end of March average (left).