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--- living_in_new_zealand:new_zealand_climate [2011/07/05 21:14]
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-===== Niwa review of NZ weather 2008-2009 =====
+===== Niwa review of NZ weather 2012 =====
-**(from NZ Herald)**
-Heatwaves and sudden snow bombarded the country in 2009, a year of extreme heat and cold that left many wondering which season they were in. Last year may have been fairly average by historical standards - ranking just 0.2C below the long-term temperature average of 12.5C - but the annual average masked a topsy-turvy year of sudden temperature change.
-The year got off to a dry start in January, with less than half the normal rainfall over much of the country combined with unusually warm temperatures in many places. February kicked off with a heatwave from the 7th to the 12th, and many places topped 34C. But those who thought they were in for a toasty year were due for a shock. Chilly southerly winds plunged temperatures to their coldest in May in many places, with an extra dose of rain on top.
-The National Institute of Water and Atmospheric Research's climate summary for the year reveals May was 1.6C colder than the 1971-2000 average for the month (calculated using records from seven long-standing climate stations). The coldest May recorded was in 1913, when the national average temperature was a bone-chilling 2.9C below normal. The early chill ended abruptly in August, which was thehottest nationally at 10.2C since records began 155 years ago.
+==== Overview ====
-All regions broke records for average August heat as northwesterly winds delivered an early spring. It was not to last. The coldest October since World War II brought heavy snow dumps to Hawkes Bay and the central North Island and trapped unwary motorists in their cars. "We typically say winter is the months of June, July and August [but in 2009 we said] there was an early onset to winter and spring," said Niwa climate scientist Dr Andrew Tait. "Unfortunately it got cool again in October, so spring didn't last very long." Dr Tait said it was relatively common over the past 100 years for winds to get stuck in a particular pattern, as they did in May and August, and deliver an unusually hot or cold month. Last year May and August occurred close together, resulting in an off-kilter year. Dr Tait said the temperature extremes could not be explained by moderate El Nino conditions, which replaced La Nina conditions as the broad climate setting in spring. "Sometimes the weather just happens."
-Meanwhile, Whakatane was again pipped at the post for the title of sunniest town after its annual sunshine could not be calculated because of instrument problems. The Bay of Plenty sun-trap hotly disputed 2008's result, after Niwa questioned the reliability of its sunshine sensor and awarded the gong to Blenheim.  Whakatane's 2009 total from May to December (1614 hours) was one hour less than the sunniest town - Nelson - over the same eight months, but figures for the rest of the year could not be calculated.
+The year 2012 was rather dry and sunny in western areas of both Islands, but annual rainfall in eastern areas of both Islands was generally near normal or above normal. Many regions experienced a somewhat cool year.
-Of the main centres, Tauranga was the warmest and sunniest, Wellington the wettest, and Christchurch the driest. Auckland was much drier than usual, having 81 per cent of its usual rainfall. It was 0.7C cooler than normal with a mean temperature of 14.6C, and 8 per cent sunnier than average.
+Annual mean sea level pressures were slightly lower than usual across New Zealand in 2012, but the circulation anomaly for the year was rather weak. More easterly circulation than normal affected the country for the first five months of the year, as well as in August. A change took place in the second half of the year, with more frequent southwesterly airflows than usual in June, September, October, and November. July and December were influenced by frequent anticyclones, and more northerly quarter winds, overall.
-Most of the six main centres were slightly colder and sunnier than usual. Wellington was the exception with higher-than-usual rainfall, cooler-than-average temperatures and about average sunshine.
+The large-scale climate setting was primarily driven by a moderate La Niña event at the start of the year, but this eased back to neutral in autumn. Although ocean temperatures in the equatorial Pacific Ocean reached the El Niño threshold by spring, the atmosphere did not develop an El Niño pattern and neutral conditions continued through the remainder of 2012.
-Avalanches became a risk towards winter's end after a long snow season was topped off with hot weather in August.
+Mean annual temperatures were below average in the northeast of the South Island, as well as for Wellington, Wairarapa, parts of the Manawatu, and between the Tararua District and the Waikato. Mean annual temperatures were generally near or slightly below average elsewhere. The nation-wide average temperature for 2012 was 12.5°C (0.1°C below the 1971–2000 annual average), using NIWA's seven-station temperature series which begins in 1909 .
-WEATHER WINNERS
+Annual rainfall totals for 2012 were below normal (less than 80 percent of annual normal) in western areas of the North Island between Wanganui and the Kapiti Coast, and for Fiordland. It was the driest year on record for Wanganui and Secretary Island. It was also a relatively dry year (with rainfall between 80 and 100 percent of annual normal) for the south, west, and north of the South Island, and across much of the remainder of the North Island (except for Gisborne). Above normal rainfall (more than 120 percent of annual normal) was observed in Gisborne, as well as for parts of Central Otago, and between Oamaru and Timaru.
-Warmest place: Whangarei, with an average temperature of 15.8°C.
+The year 2012 was a sunny one for western areas of the North Island from Te Kuiti southwards to the Kapiti Coast, as well as for the West Coast of the South Island. It was the sunniest year on record for Te Kuiti, New Plymouth, Paraparaumu, and Greymouth. This sunshine pattern reflects the enhanced easterly winds that occurred for the first five months of the year, as well as in August. In contrast, below normal annual sunshine totals (below 95 percent of annual normal) were observed for the Wairarapa, Wellington, Blenheim, Central Otago, and Northland. Elsewhere, sunshine totals were generally close to the annual normal.
-Highest extreme temperature: Culverden in Canterbury with 38°C, Feb 8.
+The year 2012 will be remembered for extremely heavy snowfall on 6 June. Snowfall was heavy and to very low levels over Canterbury, Arthur's Pass, Otago, West Coast, and Marlborough. Afternoon temperatures in Canterbury, Blenheim, around Arthurs Pass, and on the West Coast on the 6th set new low records for the month, and in some cases, broke all-time (any month) records, too. Maximum temperatures on 6 June in Canterbury struggled to reach even 1 degree, with heavy snow falling throughout the daylight hours.
-Coldest extreme temperature: -11.7C recorded at Middlemarch, July 19.
+And it was a year in which 14 tornadoes or waterspouts were observed, including a tornado which touched down near Hobsonville, Auckland, on 6 December, tragically killing three people.
-Strongest wind gust: 184km/h at Southwest Cape, Stewart Island, Nov 4.
-Most rain in a single day: Mt Cook with the top three one-day rainfalls - 341mm on April 27, 321mm on May 16 and 295mm on April 26.
+Severe frosts were widespread and frequent in the second half of June; and unusually late frosts on 7 and 8 November were problematic for some.
-Driest place: Ranfurly in Central Otago with 263mm of rainfall.
+Heat waves and extreme high temperatures were generally lacking in 2012. In January and February, La Niña's cloudy and wet conditions meant that the typical summertime swelter was absent. In contrast, winter warmth was periodically observed – with northerly winds producing unusual warmth during the second half of July, 25-27 August, the last two days of September, and the last week of October. Ex-Tropical Cyclone Evan slowly approached the northern North Island between 22 and 27 December, dragging very warm and humid subtropical air onto the country. Humidity levels were very high during this period over the North Island. The northeast air stream also produced extremely high Christmas Day and Boxing Day temperatures in western areas which were in the 'lee', namely Taranaki to Wellington, as well as Nelson. Elsewhere, numerous extreme maximum temperature records occurred during the week around Christmas due to warm windy northwesterly conditions.
-Wettest place: Cropp River in the Hokitika River catchment with 10,956mm.
-Wettest main centre: Wellington with 1274mm.
+In 2012, there were eight particularly notable rainfall events. On 22-23 February, heavy rain caused flooding and slips in Otago, Nelson, and the central North Island. A weather 'bomb' during 3-4 March caused heavy rain and extremely strong winds for the western and southern North Island, and Nelson. On 19 March, Northland was affected by widespread floodwaters due to a deep low stalling east of the Bay of Islands. This low moved south over the North Island on 20 March, all but isolating Gisborne by causing slips and tree-falls that blocked numerous roads. On 5 June, the northwest South Island was affected by record-breaking rain, associated with a rapidly deepening low over the Tasman Sea. On 16 July, flooding was widespread in many regions over the southern half of the North Island and the northern South Island. Westport was isolated, and numerous State Highways were closed due to slips and floodwaters. The Western Bay of Plenty and Coromandel were flooded in back-to-back events on 23 and 30 July. And several heavy rain events in the period to 1-15 August flooded parts of Marlborough, Canterbury, and north Otago.
-Driest main centre: Christchurch with 589mm.
-Sunniest town: Nelson with 2571 hours, followed by Tauranga (the sunniest main centre) with 2540 hours.
-Pipped at the post award: Whakatane, whose annual sunshine could not be calculated because of instrument problems. Its eight-month total from May to December (1614 hours) was just one hour less than Nelson's.
 ===== NIWA =====