Climate Summary for September 2008

September 2008: Mild start to spring

• Temperature: Above average for most of the country, especially in South Canterbury, and Central Otago.
• Rainfall: Low in Northland, Auckland, Waikato, Coromandel, and all of the east coast of the North Island; high in Wellington, Nelson, and Central Otago.
• Sunshine: Above average for much of the North Island (with the exception of Kapiti and Wellington), North Canterbury, and South Otago.

September temperatures were well above average (more than 1.5°C above their normal values) in South Canterbury and Central Otago. The majority of the remainder of the country (with the exception of Auckland, coastal Waikato, eastern Bay of Plenty, Hawke’s Bay, Wairarapa, and the northern West Coast – where temperatures were at or slightly above average) was more than 0.5°C above their average September temperature. Many eastern locations experienced their highest September temperatures on record on the 23^rd during strong north-westerly conditions. Timaru recorded 26.8°C, Dunedin recorded 25.6°C, Kaikoura got to 25.5°C, and Nugget Point recorded 23.9°C (all records for September for the respective locations). A cold spell persisted for three days from the 4^th to the 6^th when maximum and minimum temperatures in some areas were at or near record low values. The national average temperature of 11.1°C was 0.7°C above average for September.

Rainfall in September was below normal for many areas (after significantly higher than normal rainfall in both July and August), particularly in parts of Northland, Auckland, Waikato, Coromandel, and the east coast of the North Island where less than 50% (half) of normal rainfall fell. Most other areas received near-normal rainfall for September, with the exception of Wellington, Nelson and Central Otago where rainfall totals were between 150% (one and a half times) and 200% (twice) the normal values.

There were much fewer extreme weather events during September compared with July and August. The north-westerly on the 23^rd which brought the very high temperatures to eastern locations also resulted in very high rainfall at Mount Cook (236 mm) and high winds (greater than 100 km/hr) across much of Otago. On the 27^th, snow fell to about 200 m in Otago and Southland, accompanied by strong winds with gale-force gusts.

The generally mild and settled weather for September resulted from more anticyclones well to the east of New Zealand, extending ridges back across northern New Zealand, with more northerlies than normal over the country. 

Further Highlights

• The lowest temperature during September was recorded at Alexandra on the 6^th, where the minimum temperature was -6.0°C. The highest temperature during September 2008 was 26.8°C, recorded at Timaru on the 23^rd during a strong north-westerly air flow.
• The highest 1-day rainfall was 236 mm recorded at Mount Cook on the 23^rd (the third highest 1-day total for September at this location since records began in 1928).
• The highest wind gust for the month was 169 km/hr at Castlepoint on the 27^th, the highest September gust speed for this location since records began in 1972 (this same location had the highest gust for the nation last month as well; 128 km/hr on the 22^ndof August).
• Of the five main centres, Auckland was the warmest and sunniest, Wellington was the wettest, and Christchurch the coldest and driest.

Temperature

Mean temperatures were above average for most of the country, especially in South Canterbury and Central Otago where temperatures were more than 1.5°C above the September average.

Rainfall

Less than 50% (half) of normal rainfall fell in parts of Northland, Auckland, Waikato, Coromandel, and the east coast of the North Island. Other areas received near-normal rainfall for September, with the exception of Wellington, Nelson, and Central Otago where rainfall totals were between 150% (one and a half times) and 200% (twice) the normal values.

Sunshine

September totals of bright sunshine were well above average (more than 125% of normal) for Waikato, Hawke’s Bay and from Christchurch to Kaikoura and above average (between 110 and 125% of normal) for much of the remainder of the North Island (with the exception of Kapiti and Wellington) and South Otago. Sunshine totals were below average (less than 90 percent of normal) in Kapiti, Wellington, Tasman, North and Central Otago, and western Southland.

Full report

• Full details of the September 2008 Climate Summary

Climate statistics tables

Climate statistics September 2008

For further information, please contact:

Dr Andrew Tait – Climate Scientist NIWA National Climate Centre – Wellington Phone +64 4 386 0562 Mobile +64 27 327 7948 [email protected]

Dr Brett Mullan – Principal Scientist NIWA National Climate Centre – Wellington Phone +64 4 386 0508 [email protected]

Acknowledgement of NIWA as the source is required.