2007

Thursday, 10 January 2008

2007: much drier than average in many places, but disastrous floods in Northland. Drought, destructive tornadoes, windstorms, variable temperatures.

New Zealand’s climate for 2007 was marked by too little rain in many places, and record low rainfalls in some locations. Rainfall during the year was less than 60 percent of normal in parts of Marlborough, Canterbury and Central Otago, with some places recording their driest year on record. Parts of the south and east, Bay of Plenty and Wellington recorded one of their sunniest years on record too. The national average temperature was of 12.7°C during 2007 was close to normal. This was a result of some warm months (May being the warmest on record) offset by some cooler months.

“Notable climate features in various parts of the country were disastrous floods in Northland with very dry conditions, and drought in the east of the North Island”, says NIWA Principal Scientist Dr Jim Salinger. “As well there was an unprecedented swarm of tornadoes in Taranaki, destructive windstorms in Northland and in eastern New Zealand in October and hot spells. Of the main centres Dunedin was extremely sunny and dry, and it was dry in the other centres.”

“The year saw a swing from an El Niño to a La Niña climate pattern. The start of the year was dominated by a weakening El Niño in the equatorial Pacific. From September onwards La Niña conditions had developed in the tropical Pacific, with a noticeable increase in the frequency and strength of the westerlies over New Zealand in October and then a significant drop in windiness from November. Moderate to strong La Niña conditions had developed by the end of the year. Overall more anticyclones (‘highs’) occurred over New Zealand.”

“There were numerous heavy rainfall events during 2007, of which about 9 produced floods. Notable snowfall events occurred on relatively few occasions. There were 14 damaging tornado events for New Zealand for the year, an early autumn and late spring hot spell, two severe hailstorms, and seven damaging electrical storms” said Dr Salinger.

The year in review

The year began with low rainfall and significant soil moisture deficits, especially in the east, which persisted in the east of the North Island until May. A 1-day hot spell occurred near the end of January in Hawke’s Bay with temperatures reaching 34°C, and exceeding 30 °C in most other eastern regions. The most disastrous Northland floods for many decades occurred in the Far North and Whangarei districts, especially in the Bay of Islands area at the end of March, due to exceptionally high rainfall ranging from 250 to more than 400 mm occurred in eastern Northland. April was a relatively dry month overall, especially over the North Island, and in the north and west of the South Island. Warmer than normal seas to the west, anticyclones to the east, and frequent warm northwesterlies over New Zealand, produced record high mean May temperatures for New Zealand overall and the driest May on record in the north of the north and east of the country. The national average temperature was 12.4 °C (1.7 °C above normal); the highest for New Zealand as a whole in reliable records dating back to the 1860s.

June was a wintry month in the South Island, especially in the south, with frequent bitterly cold southwesterlies producing snowfall to low levels in Southland, Otago, and South Island high country passes. Severe frosts occurred after the snow. July was a month of extremes and contrasts with depressions often tracking over, or to the north of, the North Island producing floods in parts of Northland (over 400 mm in some areas), Hawke’s Bay, coastal South Canterbury, and Otago, damaging windstorms in Northland, Auckland, and the Coromandel, and thunderstorms and damaging tornadoes in Taranaki (severe), Auckland, and Bay of Plenty. More settled, although rather cold, conditions existed for much of the month in Central Otago and inland Southland, often with periods of freezing fog. At Lauder, air temperatures were constantly below zero from July 12^th to 21^st, and there were 13 days from July 7 to 22 with minimum air temperatures below -10.0 ºC. August was windy at times with frequent disturbed southwesterlies, especially to the east, resulting in low rainfall in sheltered northern and eastern South Island regions, and normal or above normal rainfall in most other regions. It was particularly sunny in Wellington, Nelson, and inland areas of south Canterbury. September was a relatively benign month with more anticyclones, less wind than normal, and generally below average rainfall.

October was rather stormy and generally cold with deep depressions tracking south of New Zealand and frequent westerly gales. This was the 4^th windiest October overall in regard to westerlies in measurements that commenced in 1966. Wind gusts over 130 km/h were recorded on 13 days (42%) in the month. In fact, many stations had at least 7 more days with strong winds (with gusts to 60 km/h or more) than is average for the time of year. Low rainfall occurred in many regions in November 2007, especially in the South Island, with totals less than 10 mm throughout much of Nelson, Marlborough, and Central Otago, and severe soil moisture deficits resulted from the lack of rainfall in parts of Hawke’s Bay, Marlborough, Canterbury, and Otago. Extremely warm conditions with maximum temperatures of 30 ºC or more occurred in many eastern regions between 20 and 26 November. The month was one of the sunniest November’s on record in Golden Bay, Nelson, Marlborough, Taranaki, and inland areas of Canterbury.

December 2007 was characterised by near or below normal rainfall in many regions, with severe soil moisture deficits persisting in Marlborough, Canterbury, North and Central Otago. The month had a wet start in Northland followed by more settled conditions. Temperatures were above average in most northern and western regions, but near average in the east. Southland and Otago basked in well above average sunshine. However, cloudy skies prevailed with near or record low December sunshine hours in parts of Northland, Waikato, and Taranaki.

NIWA analyses of month-by-month records and preliminary end of year data show:

• The highest annual mean temperature recorded for the year was 16.0°C recorded at Whangarei Airport.
• The highest recorded extreme temperature of the year occurred in Hawke’s Bay, being 33.5 °C recorded at Napier Airport on 22 January during hot dry northwesterly conditions.
• The lowest air temperature for the year was -15.4 ºC recorded at Lauder on 18 July the lowest there since July 1995 (-19.7 ºC), with numerous other inland South Island locations recording minimum air temperatures below -10.0 ºC at times between 7 and 22 July.
• May was the warmest in reliable records dating back to the 1860s.
• The highest recorded wind gust for the year (as archived in the NIWA climate database) was 170 km/h was recorded from the west, at Taiaroa Head (Otago coast) during violent storm conditions on 23 October. A higher wind gust of 180 km/h was reported on the offshore island of Tititiri Matangi between 9-11 July.
• An extraordinary swarm of damaging tornadoes wrecked havoc throughout Taranaki over 4-5 July.
• The driest rainfall recording locations were Alexandra in Central Otago with 272 mm of rain for the year, followed by Lauder with 291 mm, and then Clyde with 294 mm.
• Of the regularly reporting gauges, the Cropp River gauge in Westland, inland in the headwaters of the Hokitika River, recorded the highest rainfall with a 2007 annual total of 8940 mm.
• Christchurch was the driest of the five main centres with 510 mm and Auckland the wettest with 1096 mm. Hamilton received 952 mm, Wellington 1070 mm, and Dunedin 599 mm.
• Blenheim was the sunniest centre in 2007, recording 2567 hours, followed by Lake Tekapo with 2554 hours, then Whakatane with 2551 hours. Wellington was the sunniest of the five main centres with 2231 sunshine hours, closely followed by Christchurch with 2221 hours. Auckland recorded 2080 hours, Dunedin 1853 hours and Hamilton 1922 hours.

Prevailing climate patterns – A change from an El Niño early in the year to La Niña from spring

Overall, mean sea level pressures were above average over New Zealand, with more anticyclones (‘highs’) than average in the Tasman Sea and over the country. This pattern resulted in less wind than is normal, for much of the year, over a lot of New Zealand. This gave more frequent winds from the south and southwest over the South Island. Warmer than normal sea temperatures prevailed around New Zealand from mid autumn through late winter, disappearing over spring, and becoming cooler toward the end of the year.

A weakening El Niño occurred in the equatorial Pacific during January, with neutral conditions by the end of February. A weak-moderate La Niña developed from September onwards, strengthening as the year progressed. Over New Zealand, monthly wind-flow anomalies were highly variable throughout the year. However, warm northwesterlies were persistent in May, cold wintry southerlies prevailed in June, wet easterlies occurred in July, windy southwesterlies in August, unusually strong westerlies in October, very dry anticyclonic conditions in November, and more northeasterlies in December.

Rainfall: Below normal throughout much of New Zealand, above normal in Northland

2007 annual rainfall was below average throughout much of New Zealand. Annual rainfall was less than 75 percent of normal in the east from Wairarapa to Otago, as well as eastern Bay of Plenty, Taranaki, Gisborne, Manawatu, Wellington, and Nelson, and less than 60 percent of normal in parts of Marlborough, Canterbury, and Central Otago, many locations recording their driest year on record. Lauder recorded its driest year in more than 60 years, with only 291 mm for the year.

Northland was the only region where rainfall was above average (at least 110% of normal).

Extremely low annual rainfall, for the year 2007 was measured at:

Location	2007 rainfall (mm)	Percentage Of normal	Year Records began	Comments
New Plymouth Airport	1051	73	1944	Lowest
East Taratahi	573	68	1973	Lowest
Hicks Bay AWS	1194	69	1993	2rd lowest
Paraparaumu Airport	738	72	1945	2rd lowest
Palmerston North Airport	668	75	1944	Lowest
Stratford	1501	73	1961	Lowest
Okarito	2631	79	1982	Lowest
Appleby	661	68	1932	3rd lowest
Hanmer Forest	699	61	1905	4rd lowest
Darfield	504	63	1920	3rd lowest
Lake Tekapo	358	60	1927	3rd lowest
Tara Hills	345	65	1950	Lowest
Lauder	291	57	1943	2rd lowest
Clyde	294	71	1984	2rd lowest

Alexandra in Central Otago, was the driest of the sites where NIWA records rainfall, with only 272 mm (74% of average), followed by Lauder with 291 mm (57% of average). Of the regularly reporting rainfall stations, the wettest location in 2007, for which rainfall data are presently available was the Cropp River gauge in Westland, inland in the headwaters of the Hokitika River, with an annual total of 8940 mm. Milford Sound’s rainfall totalled 6902 mm (102% of average).

Of the five main centres, Christchurch was the driest with 510 mm (81 % of average) and Auckland the wettest with 1096 mm (88 % of average). Hamilton received 952 mm (82 % of average), Wellington 1070 mm (86 % of average), and Dunedin 599 mm (74 % of average).

2007 temperatures: Above normal in the north of the North Island, near normal in the east from Wairarapa to Otago

The national average temperature in 2007 was 12.7 °C, 0.1 °C above the 1971 – 2000 normal. Thus, 2007 ended up very close to the 1971-2000 normal, as a consequence of several warm offsetting some cooler months. Temperatures were near normal in most regions. However, they were above normal (by about 0.3 °C) in Northland, Auckland, Thames-Coromandel, and Western Bay of Plenty, Waikato, Taranaki, Gisborne, Marlborough, Nelson, inland south Canterbury, and Fiordland. Temperatures were about 0.3 °C below average in a few areas along the east coast from Wairarapa to Otago. The warmest local was Whangarei Airport, with a mean temperature for the year of 16.0°C (0.3 °C above normal). For New Zealand as a whole, there were five warmer than normal months (March, May, July, August, and December), and five cooler than normal months (January, April, June, October, and November). All other months had mean temperatures close to the climatological average. May with a mean temperature of 12.4°C (1.7 °C above normal) was the warmest nationally since reliable records commenced in the 1860s.

More sunshine than normal in the south and west of the South Island

Sunshine hours were more than 115 percent of normal in inland South Canterbury and Otago, with Whakatane, Wellington, Tekapo, Dunedin and Invercargill recording one of their sunniest years on record. Totals were at least 110 percent of normal in eastern Bay of Plenty, Southland, and Westland, and near normal elsewhere. Blenheim was the sunniest centre in 2007, recording 2567 hours, followed by Lake Tekapo with 2554 hours, and then Whakatane with 2551 hours.

Near or record high sunshine hours for the year 2007 were:

Location	2007 Sunshine (hours)	Normal (hours)	Departure from normal	Records Began	Comments
Whakatane	2551	2286	+12%	1957	Highest*
Kelburn, Wellington	2231	2065	+8%	1928	3rd highest
Lake Tekapo	2554	2149	+19%	1928	3rd highest
Dunedin	1853	1592	+16%	1948	Well above average
Invercargill	1882	1609	+17%	1932	Highest

* Highest from a mix of Whakatane area sites; the normal is from McGarvie Rd

2007 climate in the five main centres

Auckland was the warmest and wettest of the five main centres, and Christchurch the driest. Wellington was the sunniest, and Dunedin was the coldest.

Rainfall was below average in all five main centres. Temperatures were above average in Auckland and Hamilton, below average in Wellington and Christchurch, and near average in Dunedin. Sunshine totals were well above average in Dunedin and Wellington, and near average in the other main centres.

2007 climatological statistics for the five main centres:

Location	2007 Mean temp.(°C)	Dep. from normal (°C)		2007 rainfall (mm)	% of normal		2007 Sunshine (hours)	% of normal
Auckland	15.7	+0.4	Above normal	1096a	88	Below normal	2080	103	Near normal
Hamilton	14.1	+0.4	Above normal	952	82	Below normal	1922	96	Near normal
Wellington	12.5	-0.3	Below normal	1070	86	Below normal	2231	108	3rd highest
Christchurch	11.4	-0.2	Below normal	510	81	Below normal	2221b	106	Near normal
Dunedin	11.1	0.0	Normal	599	74	Below normal	1853	116	Well above normal

^a Owairaka  ^b Christchurch Airport

Significant extremes

The most significant extreme event of the year was the extraordinary swarm of damaging tornadoes that wrecked havoc throughout Taranaki over 4-5 July, as active frontal bands crossed the country from the Tasman Sea. The first tornado hit the central business district in New Plymouth on the 4^th. Damage was severe, with a large section of the Placemaker’s roof lifted off. 56 staff and customers were in the building at the time. Several other shops and houses were also damaged, along with cars. Damages in New Plymouth were estimated at $1.5 million. Multiple damaging tornadoes affected Taranaki on the 5^th, with a state of emergency declared in the New Plymouth District. There was a swath of damage along a 140 km front, and temporary supplies and accommodation had to be found for affected residents. At least 7000 homes throughout the region were without electricity after lightning strikes and damage to power lines. About 50 Oakura houses were damaged, of which 80 percent were destroyed. In Opunake, eight people were trapped in a motor vehicle surrounded by damaged, but live, powerlines. Many other areas were also affected. Damages from the tornadoes in Taranaki were estimated at $7 million.

The worst snowfall event during 2007 occurred over 20-25 June to low levels again in Southland, Otago, and the South Island high country, with Reefton, Hanmer Forest, and the North Island’s Desert Road also affected after the 22^nd. The Napier-Taupo Road was also closed on the 25^th, as well as the Rimutaka Hill Road. More than 30 cm of snowfall accumulated at St Arnaud in the Nelson Lakes district. Snowfall (8 cm) settled in Reefton, their biggest snowfall event since 1969. Lake Tekapo had 12 cm of snow on the 25^th. Further south, snowfall accumulated in and near Queenstown (4 cm in the town, 12 cm at Arthur’s Point, and 16 cm in Arrowtown – some lying until the 30th), making it difficult for cars travelling without chains. Queenstown airport was closed. Snowfall occurred to sea level around Dunedin, with up to 10 cm in the hills on the 23^rd. SH1 to Clinton was closed (there was 5 cm of snowfall at Balclutha), and many roads were icy and treacherous. In Central Otago there were some abandoned cars. An international student died when the car she was a passenger slid off the Makarora-Lake Hawea Road on State Highway 6 and crashed into the lake. Three other women survived and were taken to hospital suffering from hypothermia. State Highway 80 to Mt Cook, State Highway 83 between Kurow and Omarama and State Highway 6 between Makarora and Haast were closed. Blackstone Hill, north Otago recorded 26 cm of snow on the 21^st, with 30 cm at Lake Manapouri on the 22^nd. State Highway 73 between Arthurs Pass and Otira, and the high country of the central South Island, and many other southern and inland South Island Roads were closed during this event.

The worst flooding events during 2007 was those of 28-29 March and 10-11 July. During the first event in historical daily rainfall records were swept aside in eastern parts of Northland. Rainfall ranging from 250 to more than 400 mm occurred in eastern Northland. The floods were the most disastrous for many decades in the Far North and Whangarei districts, especially in the Bay of Islands area. Some buildings were washed away, and homes flooded, and many motorists were stranded on flooded roads. Initial estimates put the cost of damage from the floods up to $80 million. Losses of stock and agricultural production also occurred in low-lying areas. A states of emergency was also declared in the far north as heavy rainfall producing widespread severe flooding throughout much of Northland on the 10^th. Floodwaters and several massive landslips resulted in the closure of many roads. There were many landslips between Whangarei and Opoua. Water supplies were also affected. Thousands of residents were without phones and electricity, and some forced to evacuate their homes. The town of Kaeo was worst hit, with 254 mm of rainfall in 12 hours, and at least 23 houses flooded, the water being 1m high in places. At one stage, Whangarei was completely blocked off by floodwaters and slips. In Kaitaia, floodwaters resulted in the evacuation of a rest home and pensioner flats. A house at Totara North was damaged by a landslip. Damage from the flooding (which was also combined with high winds) was estimated to be almost $60 million, with almost 70 houses left uninhabitable.

Windstorms (not including tornadoes) occurred on numerous occasions, particularly severe events occurring in July and October. A state of emergency was declared over 9-11 July in the far north as damaging easterlies affected Northland, Auckland, and Coromandel, with roofs lost, containers toppled, fallen trees, broken power lines, boats washed ashore. More than 140,000 people were without electricity throughout Northland, Auckland, and the Coromandel A wind gust of 180 km/h was recorded on the offshore island of Tititiri Matangi.

In October, high winds from the west and northwest were more much frequent than normal. On 3 October, high winds resulted in the cancellation of many flights in and out of Wellington Airport. Winds on 4 October, resulted in power outages for Canterbury residents, some roofs were lifted, and a campervan was also toppled by the wind, along with fallen trees. A wind gust of 163 km/h was recorded at Tasman Aerodrome, Mt. Cook, during violent storm force northerlies. On 23 October, storm force north westerlies buffeted the southwest of the South Island, lifting roofing iron, downing power lines, and felling trees in Southland. Damage also occurred in Hawke’s Bay, Manawatu, Otago, and Canterbury (with trucks toppled).

Full report

Climate Summary for 2007 (PDF 298 KB)

For further information, please contact:

Dr Jim Salinger – Principal Scientist, Climate NIWA National Climate Centre – Auckland Phone +64 9 375 2053 [email protected]

Stuart Burgess – Climatologist NIWA National Climate Centre – Wellington Phone +64 4 386 0569 [email protected]

Geoff Baird – Communications Manager Phone +64 4 386 0543 [email protected]

Acknowledgement of NIWA as the source is required.