Where has all our snow gone?
Posted at 6:00am Thursday 27 Aug, 2020 | By Pat Deavoll email@example.com
So why so little snow for us this year?
It's fully a function of mild temperatures and lack of rain according to Chris Brandolino, principal scientist at the National Institute of Water and Atmospheric Research (NIWA).
"Wanaka is on track for its fourth driest August on record," he said. "It has only had seven millilitres of rain this month.That underscores the fact that it is dry and there is little snow.”
Also, we haven't had many southerlies, he said. "The air isn't coming from anywhere cold. And the ocean temperatures have been pretty warm during the winter season, and as an island nation, our air temperatures are closely aligned with our ocean temperatures.
“If our ocean temperatures are colder, so as a rule are our air temperatures.”
As we are entering spring and our ocean temperatures are warmer than usual, this is setting us up for a warm spring, he said. NIWA is forecasting above-average temperatures for New Zealand for September, October and November.”
Brandolino said a La Nina weather pattern hasn't formally developed, but the country is moving towards that. The ocean and the tropical Pacific are starting to resemble what NIWA would typically call La Nina, but some things have to happen.
"You want the atmosphere to acknowledge that there has been a change in the ocean temperatures and that hasn't happened with any sustainability,” Brandolino said.
La Nina events have different impacts on New Zealand's climate. More northeasterly winds are characteristic, which tend to bring moist, rainy conditions to the northeast of the North Island, and reduced rainfall to the south and south-west of the South Island.
Therefore, some areas, such as central Otago (and Wānaka) and South Canterbury, can experience drought in La Nina. Warmer than average temperatures typically occur over much of the country, although there are regional and seasonal exceptions.
"But because we are moving in that direction, when we get episodes where we get easterly/northeasterly winds this tends to promote dryness in a good part of the South Island particularly areas along and west of the divide," said Brandolino.
It seems like August has been unusually dry and mild for a good part of the South Island said Brandolino.
When you look at the winter season as a whole, there are a lot of places that are normal or slightly above average temperature.
· For August, Mt Cook had its third driest August on record. This may change between now and the end of the month if they get some rain, he said.
“It has had only 52 per cent of its average rainfall. If they get some rain before the end of the month, this could go up to 60 or 65 per cent, but this is still significantly lower than the average.
“Mt Cook is on track for its second warmest August on record. Records go back to 1929. Temps are 2.2 degrees Celsius above the average for August.”
· Wanaka Airport has had above average temperature so far.
· Middlemarch is on track for its driest August on record, and the records go back to 1896.
· Manapouri, Cromwell, Clyde, and a score of locations are all on track for a record dry August.
· Lake Tekapo had well above average air temperatures and is on track for its second warmest August on record.These records go back to 1927. As of August 23 temperatures in Tekapo were 2.4 degrees Celsius above average.
· Manapouri is tracking for the fourth warmest August on record.
· Alexandra is on track for the fourth warmest winter on record.
· Queenstown and Manapouri have below-normal rainfall for the winter season.
· Arthurs Pass has only had 54 per cent of average rainfall for the entire winter season.
What we define as an above-average is anything that is above .5 degrees Celsius on the warm side, Brandolino said.
“And of course its climate change,” he said. “What we have seen in particular regarding temperature is that it's aligned with climate change.”
View edition 989 of the Wānaka Sun here.