November's 'unsettled' weather brought record-breaking heat

Wednesday, 4 December 2019

New Zealand had a warmer than normal November, and it's all thanks to Australia.

The average temperature for the month was 15.3 degrees Celsius - 1.55C above NIWA's 30-year data, which exceeded the 1954 and 2013 November records of 1.38C above average.

An increase in north-westerly winds and a decrease in southerlies were to blame, according to NIWA climate scientist Gregor Macara.

'There's really warm air masses arriving to New Zealand from Australia … [it's] happening more frequently.'

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The mean maximum temperature in Hawke's Bay was 26.2C, up from its 25.6C average the year prior, and Kawerau had three days of incredible, record-breaking heat - 34.6C on November 3, 33C on November 4, and 32.1C on November 5.

Taupō and Rotorua also exceeded 30C, and Wairoa reached 34.1C.

NIWA principal climate scientist Dr Brett Mullan noted the last 10 days of the month averaged 0.5C above average December temperatures.

If December's temperatures continued the record-breaking trend, 2019 could become the fourth warmest year on record.

The current outlook for summer was looking warm and wet, with warmer water temperatures influencing warmer air temperatures, and a potential wind change bringing rainfall.

Spring was considered to be changeable and unpredictable, in terms of weather, and the last month of the season didn't disappoint.

'Despite the fact that it was really warm, we still had several episodes of unsettled weather - tens of thousands of lightning strikes, hail falls, the tornado down in Christchurch, as well.'

Heavy hail storms, which hit both islands, and the 66,000 lightning strikes recorded around New Zealand and the Tasman Sea in just one day made November a notable month of extreme weather.

But the 'unsettled' weather and warmer temperatures weren't shocking.

'We're quite frequently now seeing near record warm temperatures being observed in New Zealand these days and the main real reason for that is climate change.

'As the climate gets warmer, the likelihood of these hotter temperatures increases as well.'

In his six years at NIWA, Macara said record-breaking high temperatures were more frequent than record-breaking low temperatures - 'it's not even a contest'.

'High record after high record keeps getting struck … here we go again.'

While warmer temperatures might be welcomed by some Kiwis - especially those in Southland - it represented a bigger issue. The Paris Accord's target of limiting warming to 1.5C was already being exceeded in New Zealand alone, Macara said.

'The path is pretty clear in terms of where we're heading if we don't … mitigate climate change.'