Autumn 2010

03 June 2010

Warm & wet South Island, sunny North Island.

Temperature: Above average for much of the South Island, and eastern coastal fringe of the North Island. Generally near average autumn temperatures elsewhere.
Rainfall: Extremely wet in the southwest South Island; dry in Waikato and Manawatu-Wanganui. In the eastern South Island, a dry start to autumn but heavy rains last half of May.
Sunshine: Very sunny in the eastern North Island. Cloudy for the West Coast and Fiordland.
Soil moisture: Significant soil moisture deficits persisted through most of autumn in many areas of the North Island, Marlborough and Canterbury. Heavy rainfall at the end of May brought soil moisture to capacity in all regions, except Waikato and Manawatu-Wanganui.

During autumn, the El Niño event dissipated. March was extremely dry in the north and east of the North Island, and South Canterbury and Otago. April saw continued dryness over the North Island, but extremely large rainfalls for the southwest of the South Island, linked to enhanced northwesterly winds there. Significant soil moisture deficits continued during March and April for much of the North Island, Marlborough and Canterbury. However, in May, there was a change to stormy conditions, with more frequent northeasterly winds over the country. This produced extremely high rainfalls and several flood events in eastern regions of both Islands. By the end of May, soil moisture levels were at capacity in all regions except Waikato and Manawatu-Wanganui, which remained drier than normal.

Autumn mean temperatures were above average (between 0.5°C and 1.2°C above average) over much of the South Island, as well as along a coastal fringe in eastern areas of the North Island. In parts of Canterbury and Central Otago, seasonal temperatures were well above average (more than 1.2°C above average). Temperatures were generally near average elsewhere. The New Zealand national average temperature for autumn was 13.8°C (+0.5°C above the 1971-2000 autumn average).

Overall, it was a dry autumn in the Waikato and Manawatu-Wanganui regions (with rainfall between 50 and 80 percent of seasonal normal), but extremely wet in the southwest of the South Island (with totals more than 125 percent of autumn normal). In the east of the South Island, where autumn rainfalls were well above average in many areas (more than 150 percent of normal), most of the autumn rain fell in the last half of May. Elsewhere, autumn rainfalls were generally close to normal.

It was an extremely sunny autumn for the eastern and central North Island, with above normal sunshine totals (between 110 and 125 percent of autumn normal). In comparison, it was a cloudy autumn for Nelson, the West Coast, Fiordland, and parts of Otago, with sunshine totals less than 90 percent of seasonal normal. Elsewhere, sunshine totals were close to autumn normal.

Major highlights

The highest temperature was 32.7°C, recorded at Cromwell on March 9th (a new autumn record) and the lowest temperature was -5.2 °C, recorded at Windsor on May 6th (not an autumn record).
The highest 1-day rainfall was 314 mm, measured at Milford Sound on April 25th (not an autumn record).
The highest wind gust was 216.8 km/hr, recorded at Baring Head, Wellington, on March 12th (a new autumn and all-time record at this site).
Of the six main centres this autumn, Tauranga was the warmest and sunniest, Dunedin the coolest, Wellington and Tauranga equally the wettest, and Hamilton the driest.