Climate Summary for August 2008

August 2008: Another very wet and stormy month (July 2008 was also very wet in many places) for most of the country

• Temperature: Near average (plus or minus 0.5°C) for the North Island; below average for the South Island, particularly inland Canterbury and coastal North Otago (1 to 2°C below average).
• Rainfall: Well above normal rainfall (more than 150% of normal) in Marlborough (especially Kaikoura), Canterbury, Tasman, eastern Southland and the majority of the North Island; below normal rainfall (less than 80% or normal) in Gisborne, Hawkes Bay, parts of the Southern Alps, Central Otago and Fiordland.
• Sunshine: Well above normal (more than 125% of normal) hours of bright sunshine recorded for coastal Gisborne and East Cape; above normal (between 110 and 125% of normal) for Northland, eastern Bay of Plenty, Hawkes Bay, north Canterbury, Fiordland and Southland.

August 2008 was yet another very wet month for many areas, continuing the trend from July. In the North Island from Auckland south with the exception of Gisborne and Hawke’s Bay, rainfall totals were greater than one and a half times (150%) their normal values for the month. In the South Island there was a strong northeast to southwest gradient with Marlborough receiving over 300% of normal August rainfall (three times) while the Southern Alps, Fiordland and Central Otago received less than half their normal August allotment. In terms of other extremes, once again (similar to the previous month) there were several storms during the month bringing a mixture of snow, high winds and heavy rainfall to much of the country. In particular, the 126 mm of rain which fell in the 24 hours to 9am on the 26^th at Kaikoura (the second highest 1-day August rainfall for this location since 1898) resulted in several landslides, surface flooding, disruption of the clean water supply, road and rail closures, damage to bridges, evacuations of residents (again) and the death of many livestock including newly born lambs. On Mt Ruapehu the recorded 3.5 m of snow pack was the deepest snow base since records began in 1992, with unusually low snowfalls in some other North Island areas occurring.

August temperatures were near average in the North Island but below average in the South Island. The three days from the 9^th to the 11^th were particularly cold for many locations, with minimum temperatures as low as -5.0°C recorded at Dunedin Airport, -4.0°C at Martinborough and 1.5°C at Kaitaia (all August records). The maximum temperature only reached 5.2°C in Dannevirke on the 9^th (the lowest August maximum temperature at this location since records began in 1951), and several other locations also experienced record or near-record low maxima. The national average temperature of 8.9°C was 0.2°C below average for August. The weather system which brought the heavy rains to Kaikoura late in the month also resulted in extremely high temperatures in Haast, which experienced a minimum temperature of 12.9°C on the 25^th and a maximum temperature of 19.9°C on the 26^th; both values being the highest ever for the month of August for this location.

These extremes and contrasting patterns were caused by many more frequent depressions (‘lows’) especially just east of the North Island producing stormy westerly winds over the North Island, and south easterlies onto the South Island. Four depressions tracked over the North Island and northern South Island during the month (on 2^nd – 3^rd, 8^th – 10^th, 13^th –15^th and 23^rd – 25^th). In contrast, conditions were quiet over the southwest.

Further Highlights

• The highest 1-day rainfall was 135 mm recorded at Hanmer Forest on the 25^th (the highest 1-day total at this location since records began in 1905).
• It rained (at least 1 mm) on 23 days in August in Pukekohe (7 days more than normal). Other high rainfall-days locations were Waiouru (22 days), Auckland (21 days), Kaikohe (20 days) and Palmerston North (20 days).
• The highest temperature during August 2008 was 19.9°C recorded at Haast on the 26^th. The lowest temperature during August was recorded at Arthurs Pass on the 20^th, where the minimum temperature was -9.5°C.
• The highest wind gust for the month was 128 km/hr at Castlepoint on the 22^nd, with a gust of 124 km/hr also recorded at Puysegur Point on the same day.
• Of the five main centres, Auckland was the warmest, Wellington was the wettest and sunniest (an interesting combination), Christchurch the coldest, and Dunedin the driest.

Temperature

Mean temperatures were near average for most of the North Island but below average for the South Island.

Rainfall

Marlborough, Canterbury, coastal Taranaki, Tasman, eastern Southland and the majority of the North Island all received at least 150% (one and a half times) their normal August totals (with over 300% of normal recorded at Kaikoura), while below normal rainfall (less than 80% or normal) fell in Gisborne, Hawkes Bay, the Southern Alps, Central Otago and Fiordland.

Sunshine

August totals of bright sunshine were above normal (by more than 110 percent) in Gisborne and East Cape, Northland, eastern Bay of Plenty, Hawkes Bay, north Canterbury, Fiordland and Southland. Sunshine hours were below average (less than 90 of normal) in parts of Taranaki, Manawatu, Westland, South Canterbury and coastal Otago.

Full report

• Full details of the August 2008 Climate Summary

Climate statistics tables

Climate statistics August 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 James Renwick – Climate Scientist NIWA National Climate Centre – Wellington Phone +64 4 386 0343 Mobile +64 21 178 5550 [email protected]

 

Acknowledgement of NIWA as the source is required.