Mt Ruapehu recorded its driest October on record, in a month that was drier than normal for much of the lower North Island.
According to the October climate summary from the National Institute of Water and Atmospheric Research (NIWA), Whanganui was one of the regions which recorded below-normal rainfall.
NIWA meteorologist and forecaster Seth Carrier said this was due to the El Niño climate driver which was now in place over New Zealand.
“With an El Niño, you typically get more high pressure near the North Island and high pressure near or over the North Island can help to block rainmakers.
“High pressure typically means settled, drier weather,” Carrier said.
Conditions got drier further inland across Whanganui and Ruapehu, with the NIWA weather station at Chateau Tongariro recording the lowest amount of rainfall for the month on record at a total of 95mm, only 34 per cent of normal.
“Records at that station only begin in the year 2000, so it’s not a particularly lengthy record there but regardless it’s the driest October at the Chateau in the last 23 years,” he said.
It was also especially warm at the chateau, recording its highest-ever daily maximum air temperature at 23.8C on October 5.
Overall, it was the third warmest October for the area since records began, with a mean air temperature of 7.7C, 1.2C higher than normal.
On the southeast side of the mountain in Waiouru, NIWA also recorded its second-highest maximum air temperature since records in began 1962 at 22.6C, also on October 5.
The town also recorded its second-equal highest speed wind gust for October, clocking a speed of 106km/h.
Carrier said high winds were seen all across the country and were also the result of El Niño because as well as high pressure around the North Island, it tends to produce low pressure around the South Island.
“Essentially if you have high pressure and low pressure that are relatively close to each other you’re getting stronger winds in that scenario because essentially the high pressure is trying to move into the low pressure to fill it in.
“Between those two areas, which is essentially the country of New Zealand in itself, you tend to get a lot of wind because the high pressure and the low pressure are trying to equal each other out,” Carrier said.
Whanganui NIWA’s weather station at Spriggens Park recorded a mean air temperature of 13C which is 0.4 cooler than normal for the month.
However, this number still falls within the metrics of what is considered near-normal for the month, which is any temperature between 0.5C hotter or 0.5 colder.
A max temperature of 22.6C was recorded on October 17.
NIWA’s latest climate outlook for the coming three months said there was a 100 per cent chance of El Niño persisting over November, December and January.
Similar conditions for Whanganui to what was recorded in October were expected for November with more westerlies than normal expected.
“That being said, this El Niño could be slightly different from El Niños we’ve had in past years where we could still see periodic southerlies coming through.
“So westerly winds are probably most common but at times we could see at least brief periods of southerly or southwesterly winds, and those could bring in briefly cooler temperatures,” Carrier said.
With El Niño also expected to strengthen, November was also likely to be drier than normal for the region, especially in the second half of the month.
Near-average to above-average temperatures and near-average to below-average rainfall were expected for the next three months.
“Potentially the trends we saw through the month of October we could see kind of similar trends occur over the next few months as well.”
Finn Williams is a multimedia journalist for the Whanganui Chronicle. He joined the Chronicle in early 2022 and regularly covers stories about business, events and emergencies. He also enjoys writing opinion columns on whatever interests him.
