Weather’s tale - warm wet, dry
Last year was the fifth warmest year on record in New Zealand and one in which swings between extremes toppled longstanding records nationwide.
The annual climate summary for 2017, released yesterday by the National Institute of Water & Atmospheric Research (Niwa), shows the weather was largely defined by warm temperatures and high rainfall, but ended with record-breaking dry spells.
For most of the country, 2017 was warmer and wetter than usual, the report says. All six major cities clocked up their usual annual rainfall before the end of September and were on track for record wet years.
Many areas broke or nearly broke various high temperature records.
Of the major cities, Auckland was the warmest, Dunedin the coldest and driest, Tauranga the wettest and sunniest, and Wellington the most dim.
The average air temperature nationwide was 13.15 degrees Celsius, about 0.5C above the longterm average. That made it the fifth warmest year since 1909, beaten by 2016, 2013, 1999 and 1998.
While much of the South Island and lower North Island had near normal temperatures, temperatures were above average further north.
The exceptions to the overall trend were in the deep south – Southland and Central Otago were notably drier than usual.
Hot streak
As the year came to an end, the country was in the midst of a record warm streak.
August, September and October was the equal warmest threemonth period in New Zealand since 1909, Niwa principal forecaster Chris Brandolino said.
‘‘We had exceptional warmth in each of those months, in particular August, where the temperature was 1.3C above average.’’
That streak continued. December was 2.4C warmer than usual, only the third time average temperatures had been above 2C in a given month.
‘‘The month of December was exceptional temperature wise – the nationwide average temperature was 18.1C, that’s 2.4C above the long-term average.
‘‘There were 90 locations where the mean temperature was a record or near record value.’’
Cromwell had 23 consecutive days above 25C, ending the month more than 3C warmer than usual.
Three storms
The defining weather events for the year were a series of storms, which were major contributors to high rainfall totals.
In particular, the ‘‘Tasman Tempest’’, Ex-Tropical Cyclone Debbie, and Ex-Tropical Cyclone Cook earlier in the year had major impacts and contributed to record or near-record rainfall.
The wettest places compared with the norm were on the east coast, particularly around the Coromandel and Tauranga, where rainfall was about 40 per cent above long term-averages.
Some areas hit by storms ended the year with near record rainfall totals. Oamaru was hit by a storm in July, which dropped four months of rain in one day. It had its second wettest year despite ending 2017 with a dry spell.
While the year was defined by rain, the dry spells near the end broke records in themselves. The Niwa report said that in terms of rainfall, it was a ‘‘year of two halves’’.
Christchurch had a 47-day dry spell, the longest in many decades, while in the midst of one of its wettest years on record.
While some low temperature records were broken, they were far exceeded by high temperature records.
Three places had their warmest years on record – Te Puke, Wairoa, and Lauder (near Clyde in Otago).
Auckland at Whenuapai had its second warmest year on record, as did Hastings. Dozens of other areas had near-record warm years.
Sun times
In terms of sunshine, the top of the South Island was once again the place to be. The wider Nelson area ended the year with 2633 hours of sun, followed by Marlborough with 2605 hours.
The warmest places were in the far north. Leigh, north of Auckland, had the warmest average temperature of 17C, followed by Whangarei and Kaitaia.
The driest towns were all in Central Otago. Clyde, Cromwell and Alexandra all had less than 300mm rainfall for the year.
Two places recorded that much rain in a single day: Castle Mount and Milford Sound.
Every month was warmer than average except for January, which was 0.7C below average.