Ready, set, go – it’s time for a warm leap into spring
It’s time to close the door on winter—spring will be here on Thursday bearing gifts of warm winds and sunshine for September.
NIWA forecaster Ben Noll says subtropical winds flowing south from near New Caledonia at the end of this week will at times make it feel more like November or December.
Mr Noll said strong high pressure is forecast to pass over the top and then move northeast of New Zealand later this week and into the weekend, drawing warmth southward. This pattern may repeat several times during the first half of September. As a result, a couple of rounds of record-breaking maximum and minimum temperatures are possible.
“We are forecasting unseasonable warmth on Thursday and Friday across the east of both islands, where temperatures may rise to between 5 and 10°C above the average maximum daily temperature. Some places may approach 25°C as a classic foehn wind develops,” Mr Noll said.
The atypical warmth is expected to expand across the North Island by the weekend and may get more impressive from Sunday for couple of days when records could tumble. A push of cooler air is possible between September 6 and 8 before the unusual warmth rebuilds. There is the potential for another round of record-breaking temperatures just after September 10.
Spring sun on its way
The warmer temperatures forecast for early September are caused in part by more sunshine. The sun’s altitude at solar noon is higher in the sky than it was a bit over two months ago at the Winter Solstice, allowing for more direct solar radiation.
This type of weather pattern is typically one that brings mostly dry conditions to the east of the South Island, a region that continues to suffer from below normal rainfall and soil moisture. The warmer than usual weather may also contribute to some ski field snowmelt, especially at Mt Ruapehu; however, since many South Island fields have healthy snow bases, the effects there might not be quite so harsh.
Meanwhile, winter has left a trail of records in its wake and has certainly made its contribution to 2016 being the warmest on record in New Zealand for the first eight months of the year.
The highest winter temperature was 25.1°C, at Napier on June 10. This was also the highest winter temperature ever for Napier. Gisborne also experienced its highest winter temperature on record with 23.2°C, also on June 10. Winter’s lowest temperature was -17.8°C, at Takahe Valley (near Te Anau) on August 7. Auckland’s wettest June hour on record was between 1 and 2 pm on June 29 when 26.6 mm of rain bucketed down on the city.
Waipara West in the north of Canterbury is tracking toward its second driest winter on record with just 73mm of rain through to August 28. This is 43% of normal winter rainfall. And Timaru is tracking for its sunniest winter on record since 1930 with 510 hours through to August 28.