Monthly Climate Summary: Extremely dry for much of North

NIWA Monthly Climate Summary: January 2013:
Extremely dry for much of North Island; wet for South Island

Rainfall
Record dry for Northland, Auckland, Waikato, Coromandel, Bay of Plenty, and Masterton. Less than half January normal rainfall across most of the North Island, excluding the coastal margin between Wanganui and the Kapiti Coast, and Wellington. In contrast, it was very wet for much of South Island. Rainfall exceeded 150 percent of January normal from Queenstown to Gore, as well as Central Otago, Nelson and Marlborough. More than double the usual January rainfall was recorded around Mt. Cook, the Kaikoura Coast, and parts of north Canterbury.

Soil moisture
As at 1 February 2013, extreme soil moisture deficit (more than 130 mm of deficit) was evident in Northland, Auckland, Waikato, the Bay of Plenty, Gisborne, Hawkes Bay, Wairarapa, as well as Wanganui to Palmerston North, around Christchurch, and in Central Otago. Significant soil moisture deficit (more than 110 mm of deficit) was generally seen elsewhere in the North Island, eastern Otago and south Canterbury.

Sunshine
Extremely sunny across New Zealand. The combination of northwest winds and the ‘blocking high’ resulted in record January sunshine across the eastern South Island.

Temperature
Above average in the east and south of the South Island, eastern Northland and Auckland, Wairarapa, and between Wanganui and Napier. Below average for coastal Fiordland and Westland. Near average temperatures elsewhere.
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Overview
January 2013 was a month of two halves – and two Islands. During the first half of the month, more northwesterly winds than usual affected the South Island, bringing unsettled weather and several heavy rainfall events to the South Island. But high pressures prevailed over the North Island during this time – meaning any fronts actually making it across the North Island “fizzled” – producing very little rainfall. The second half of January was characterised by an intense ‘blocking high’ which became slow moving over, and to the east of, the country. This produced extremely sunny and dry conditions for New Zealand over the second half of the month. The net result overall was an extremely dry January for the North Island, but a relatively wet month for the South Island.

January rainfall totalled less than 10 percent of normal across much of Northland, Auckland, Coromandel, and parts of the Waikato and Bay of Plenty. It was the driest month on record for Warkworth, Whitianga and Te Puke, and the driest January observed in Masterton. For the main population centres of Auckland, Hamilton and Tauranga, monthly rainfall totalled less than 10 mm, and ranked near-record low. Rainfall totals were less than half of January normal across much of the rest of the North Island, excluding Wanganui to the Kapiti Coast (where rainfall was below normal) and Wellington (with totals about 120 percent of normal). In stark contrast, it was a very wet January across most of the South Island. Rainfall exceeded 150 percent of January normal from Queenstown to Gore, as well as Central Otago, Nelson and Marlborough. More than double the usual January rainfall was seen around Mt. Cook, the Kaikoura Coast, and in parts of north Canterbury. Closer to normal rainfall was observed in coastal Westland and Fiordland, as well as Dunedin, Christchurch and coastal south Canterbury.

As at 1 February 2013, extreme soil moisture deficit (more than 130 mm of deficit) was evident in Northland, Auckland, Waikato, the Bay of Plenty, Gisborne, Hawkes Bay, Wairarapa, as well as Wanganui to Palmerston North, around Christchurch, and in Central Otago. Significant soil moisture deficit (more than 110 mm of deficit) was generally observed elsewhere in the North Island, as well as the remainder of Otago and south Canterbury.

The combination of northwest winds, and high pressures, resulted in record or near-record high January sunshine totals across the eastern South Island. It was the sunniest January on record for Christchurch, Cheviot, Ashburton, Lake Tekapo, as well as Waipawa (Hawkes Bay). It was also the sunniest month on record for all of these sites, except Christchurch, which logged its second-sunniest month after December 1988. Sunshine totals were generally above normal (between 110 and 125 percent of January normal) for the remainder of New Zealand, with the exception of Northland, Auckland, Wellington and Blenheim (with near normal sunshine observed).

Mean temperatures were above average (between 0.5°C and 1.2°C above the January average) in the east and south of the South Island, along the eastern coastline of Northland and Auckland, in the Wairarapa, and between Wanganui and Napier. In contrast, below average temperatures were observed for coastal Fiordland and Westland. Elsewhere, mean temperatures were near average. The nation-wide average temperature in January 2013 was 17.3°C (0.2°C above the 1971-2000 January average), using NIWA’s seven-station temperature series which begins in 1909.

Further Highlights:

• The highest temperature was 35.1 °C, recorded at Clyde on 5 January (record-equal for January there), and at Gisborne on both 9 and 10 January.
• The lowest temperature was -0.5 °C, observed at Hanmer Forest on 18 January.
• The highest 1-day rainfall was 346 mm, recorded at Mount Cook on 9 January (a new January record there).
• The highest wind gust recorded was 161 km/hr at Cape Turnagain, on 8 January.
• Of the six main centres in January 2013, Auckland was the warmest, Dunedin the coolest, Wellington the wettest, and Tauranga the driest and sunniest.

FOR FURTHER INFORMATION AND CONTACT DETAILS FOR COMMENT, PLEASE SEE THE ATTACHED DOCUMENT.

Climate_Summary_January2013_FINAL_4.2.13.pdf

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