Monster high pressure system sets new national record

A sprawling high that’s delivered sparkling blue days across the country this week - and plenty of fog to some regions - has broken a new national record for pressure, meteorologists say.

A sprawling high that’s delivered sparkling blue days across the country this week has broken a new national record for pressure, meteorologists say.

After barometers this week registered a new national mean sea level pressure record for July, of 1045 hectopascals (hPA), Ranfurly in Central Otago last night recorded a provisional all-time record of 1046.5 hPa.

“This high pressure system is among the strongest to pass over New Zealand on record, according to our national climate database,” Niwa forecaster Ben Noll said.

Such values have only been observed a handful of times in New Zealand; the last time air pressure climbed above the 1040hPA mark was October 2022.

The current world record for high pressure was 1083.8 hPa, set in Siberia in 1968.

Noll explained that air pressure represented the force exerted by the weight of air above a given point on the Earth’s surface.

In systems like the one over New Zealand now, atmospheric pressure was higher than in the surrounding regions.

“In a high-pressure system, air descends and spreads outward, typically leading to clear skies, calm conditions, and stable weather.”

As at late afternoon, the highest temperatures around New Zealand were in Kaitaia, where the mercury nudged above 15C earlier today.

The coldest values were in Twizel, where temperatures have failed to climb above freezing point throughout the day – and were forecast to plunge to –5C overnight.

“While there is certainly a lack of precipitation, some folks may be awakening to foggy or frosty conditions,” Noll said.

The run of settled, sunny weather for much of the country was forecast to take a turn beyond the weekend, with rain forecast early next week in centres including Auckland, Hamilton, Tauranga and Wellington.