A powerful high pressure zone with peak central air pressure last night of 1046.5 hPa in Ranfurly, Central Otago looks to be the highest air pressure recording in NZ’s history. Once confirmed it will have beaten the old record of 1045.9 recorded in 1889 in Wellington.

WeatherWatch said earlier this week the anticyclone had the chance of breaking records as it moved over the South Island during Wednesday and into Thursday. On Thursday morning Niwa confirmed the record appears to be broken.

The high will weaken a little and drift off to the south-east of NZ in the days ahead

📈A high pressure zone for the record books! #NewZealand https://t.co/1yFDBhoHYD

— WeatherWatch.co.nz (@WeatherWatchNZ) July 11, 2024

The higher the air pressure the drier it usually is, with clearer skies for many. The sinking air limits cloud formation but can make for fog in our valleys and inland plains that hangs around – because another thing high pressure brings is calm conditions or lighter winds. The light winds help for mild days for some in the sun, but nights are generally cold – which is why frosts are more likely in the south and inland areas.

A light easterly airflow will develop in the north of NZ with a few clouds because the centre of the high is further to the south. The further you are from the centre the more you get caught in that anticyclonic wind and cloud circling slowly around it.

That circling wind – in the coastal east and north of the North Island in particular – means cloudy areas and a few showers are possible in the days ahead, especially as a low forms well east of the North Island in an area of colder air dredged up by the high pressure zone centred over the South Island.

Powerful highs form near NZ in winter, and some can be in the mid 1040hPa range, even a bit higher – but it’s rare to have such powerful high pressure crossing land itself and this may challenge, or potentially break records here.

According to ABC News the same high pressure zone now in NZ reached 1043.9hPa at Ouse, Tasmania several days ago – only 0.5hPa below the Australian record.

THE HISTORY:
The previous highest pressure recorded in New Zealand was in Wellington in 1889 at 1046 hPa (1045.9).

1044.7 hPa was measured over the South Island on June 5, 2016 according to NIWA.

In 2008 a large high in the South Island and Chatham Islands reached 1044hPa.

• WeatherWatch.co.nz