NATIONAL CLIMATE CENTRE Monday 4 April 2011

National Climate Summary – March 2011: A mixed-bag start to autumn

• Rainfall: A wet month for the North Island, Marlborough Sounds, coastal Southland and much of Otago.
• Temperatures: Near average in most regions due to the contrast between prevailing warm northeast winds and an extreme cold outbreak on 6 March. Above average in coastal parts of the northeastern North Island.
• Sunshine: Extremely sunny on the West Coast. Cloudy for Northland and north Otago.
• Soil moisture deficits: Remain significant in Tasman District, Marlborough and parts of Canterbury.

Overall in March 2011, anticyclones (‘highs’) dominated to the east of New Zealand, bringing more northeasterly winds than normal to the country. The first week of the month was unsettled, as were the periods March 21/22 and 26/27. This resulted in a very wet March across the North Island, as well as for the Marlborough Sounds, coastal Southland, and most of Otago. But autumnal anticyclones brought dry, settled weather to many areas for the remainder of the month. Ex-tropical cyclone Bune passed east of East Cape at the end of the month.

March rainfall totals were well above normal (more than 150 percent of normal) across almost all of the North Island, as well as in the Marlborough Sounds, coastal Southland and much of Otago. Rainfall totals were generally near normal elsewhere in the South Island, except in Marlborough (where totals ranged between 60 and 80 percent of March normal). At the end of March, significant soil moisture deficit (deficit more than 110 mm) remained in the Tasman District, Marlborough and parts of Canterbury.

Monthly mean temperatures were above average (between 0.5°C and 1.2°C above March average) in eastern coastal areas between North Cape and East Cape. But for the vast majority of New Zealand, March temperatures were near average (within 0.5°C of March average) – reflecting the contrast between prevailing northeast winds bringing generally warm air onto the country and an extremely cold southerly outbreak which affected much of New Zealand on 6 March. Small pockets of below average temperatures (between 0.5°C and 1.2°C below March average) were experienced around the Central Plateau, as well as in alpine areas of Westland. The New Zealand national average temperature was 15.8°C (equal to the 1971–2000 March average).

March sunshine totals were well above normal on the West Coast of the South Island (more than 125 percent of March normal). It was the sunniest March on record for Greymouth. Auckland, the Bay of Plenty, Central Plateau, Hawkes Bay, Kapiti Coast and Wellington, Southland and Canterbury were also sunny, with totals between 110 and 124 percent of normal. In contrast, it was rather cloudy in Northland and north Otago, with below normal totals (less than 90 percent of March normal). Elsewhere, March sunshine was close to normal.

Further Highlights:
• The highest temperature recorded was 31.4°C recorded at Christchurch on 4 March.
• The lowest temperature recorded was -2.3°C recorded at Masterton on 8 March.
• The highest 1-day rainfall of 159 mm occurred at Whitianga on 21 March.
• The highest gust was 159 km/hr, recorded at Southwest Cape (Stewart Island) on 2 March.
• Of the six main centres, Auckland and Tauranga were jointly the warmest, Hamilton was the wettest, Christchurch the driest, and Tauranga the sunniest.

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