It's a crazy cold winter, and don't expect spring to be much better

Thursday, 5 July 2018

The record-breaking hot summer is now a distant memory as we battle through the winter chill. And we may be waiting longer than usual for spring to warm up this year.

Figures from Niwa show the country's mean monthly temperature - recorded at seven climate stations as part of a series that started in 1909 - was back to flat average in June.

That's down from 3.1 degrees Celsius above average in January, 0.8C above in February, 1.3C above in March, 0.1C above in April, and 0.4C above in May.

During the past six months there were 163 instances where towns or cities had record or near-record mean monthly temperatures, Niwa meteorologist Ben Noll said. On just three occasions were there record or near-record low mean monthly temperatures for any locations around the country. 

**READ MORE:

* It was officially New Zealand's hottest summer on record

* Our seas are heating up. Here's why

* Record-breaking Kiwi summer heatwave turns Auckland tropical for a week**

January to June 2018 was the fifth warmest first half of a year on record, behind 1998, 1937, 1999 and 2016.

Last summer's warmth was partly caused by unusually warm sea surface temperatures (SSTs), as persistent high pressure over the Tasman Sea prevented the mixing of cool, deeper ocean water with the surface. At the same time, the pressure pattern meant more frequent warm northerly and northeasterly winds.

The warm SSTs were probably fully gone during May, Noll said. With the La Nina weather pattern and the marine heatwave now gone, there was no distinctive player in the climate.

'That makes climate forecasting and weather forecasting to some extent more challenging.'

The warm 🌡️🌡️🌡️

From January-June 2018, record or near-record high mean monthly temps were reached a staggering 163 times.

During the same period, there were just 3 record or near-record low mean monthly temps.

That's a ratio of 1 cold extreme for every 54 warm ones. pic.twitter.com/TrT28GPa2N

— NIWA Weather (@NiwaWeather) July 4, 2018

Looking at analogue years to the current year - those with similar climate features - 'a lot have a common thread, they had a sluggish start to spring in terms of temperature', Noll said.

'There are indications for a cooler flavour. I think we may see that. It could be a bit of a slow climb. September may have some flavours of winter lingering… It may be a little more pronounced this year.'

The wet 🌧️🌧️🌧️

All of New Zealand's main centres, aside from Dunedin, have experienced more wet days than normal from January-June 2018.

Auckland has led the way with 78 wet days so far (the normal amount is 61). Hamilton is close behind at 70. pic.twitter.com/MK5DQwDZ8s

— NIWA Weather (@NiwaWeather) July 4, 2018

Winds could come from the westerly quarter more often later in August or into September, which could bring active weather to western areas, and could lead to maybe some colder weather. 

Five of the six main centres also had more rainy days - defined as having at least 1mm of rain - than average in the first six months of 2018.

Auckland had 78 compared to the average of 61, Hamilton had 70 compared to 54, Tauranga had 61 compared to 49, Wellington had 60 compared to 56, and Christchurch had 53 compared to 41. Dunedin was the exception, with 50 rainy days, compared to the average of 55.

In some respects the high number of rainy days probably was related to the marine heatwave, Noll said. The marine heatwave heated the atmosphere, enabling it to hold more water vapour.

For instance, Auckland had 16 rainy days in February, compared to an average of 7.1. That was at the peak of the marine heatwave and was also a month when the country was affected by two ex-tropical cyclones.

In contrast, in June Auckland had 17 rainy days, compared to an average of 15.