Climate Update 31 - January 2002

January

Climate

River flows

Soil moisture

Three-month outlook

Checkpoint

Backgrounder

Backgrounder

Backgrounder

Before the wet...
The year 2001 to 30 September was the driest January to September period of the past 30 years in many places (highlighted by the darkest shade of pink in the map below).

...and after
October to December rainfalls exceeded 1 in 10 year highs in central New Zealand and northern North Island regions.

2001 rainfall totals for January to September (upper map) and October to December (lower map) recorded at the sites indicated, shown according to their positions in respective rankings of all January to September or October to December rainfall totals for the past

Checkpoint

Outlook and outcome – October to December 2001
Rainfall in some central regions of New Zealand was average to above average as expected. The north and east of the North Island was wetter than forecast, while some central and southern areas of the South Island were drier than anticipated.
Air temperatures in most places were above average as was expected, although temperatures were higher than forecast in much of the east of the South Island.
Normal to below normal river flows were correctly forecast for the east of both islands.

January

Climate Update is a summary each month of New Zealand's climate, including soil moisture and river flows.
January 2002 – Number 31
December’s climate: A ‘conveyor belt’ of warm, moist sub-tropical air triggered a wet, cloudy month.
December’s river flows: Highest recorded December mean flows in some catchments.
Soil moisture levels: Saturated soils in the north.
Three month outlook: More rain ahead for the north.

Climate

New Zealand Climate in December 2001
December rainfalls set some new records
More than 150% of normal rainfall was recorded for December in the North Island and northwest of the South Island. New rainfall records for the month were set in parts of the far north (Kerikeri 240%), Hawke’s Bay (Whakatu 467%), Wairarapa (East Taratahi 253%), central North Island (Turangi 246%), and Nelson (Lake Rotoiti 222%).

Three-month outlook

The outlook for January to March 2002
The El Niño-Southern Oscillation is in near neutral phase at present. Some climate models suggest El Niño-like conditions will develop in the equatorial Pacific over the next three to six months. However, past experience shows the predictability of El Niño development in the period leading up to Autumn is low.

River flows

New Zealand River Flows in December 2001
Highest recorded December mean flows in some catchments
December mean flows were at record high levels for much of the North Island and the northern third of the South Island. Above normal flows occurred in rivers draining the Southern Alps. Flows in foothill rivers in Canterbury and Otago were normal to above normal, and Southland rivers were normal to below normal.

Soil moisture

Soil moisture on 31 December
Saturated soils in the north
In the North Island and northwest of the South Island, soils which were wetter than average at the end of November remained near or above field capacity for much of December.