May was the month of mountainous high pressure zones. Mostly based south of Australia and also to the east of the South Island, they have kept much of the South Island drier than average – although Cantabrian farmers were pleased to get some rain from the recent North Island low.
Despite that low bringing areas of flooding to the north of New Zealand, it was most likely seen as a net positive for NZ’s farming and growing industry with so many regions in a rainfall deficit lately.
High pressure remains stuck around southeastern Australia even as we turn the page on May and welcome June. But there are changes happening across the ditch with more westerlies coming in for early June and whilst NZ has had a lot of colder sou’westers this winter, a change to more westerly driven weather would be milder.
In fact that giant high pressure zone that set anchor near Tasmania half a month ago has now finally lifted the anchor and is floating again, and should be centred near northern NZ on the first day of June (Saturday). This placement usually brings in a mix of southwest to westerly quarter winds. Milder westerlies from out of the Australia region can replace the sou’westers from off the Southern Ocean. A small difference in direction with a big consequence and it can be noticeably milder when a westerly replaces a sou’wester.
The movement of this stubborn high has both negatives and positives for us. Positives might be slightly milder weather and a bit more sunshine. Negatives might be areas still in a rain shadow effect in recent months may be no better off. It still limits rain in southeastern Australia, too.
Many parts of NZ look to become drier than usual again in the weeks ahead. The weather pattern in Australasia is showing some signs of change but it all seems very slow, like the atmosphere is made of toffee.
High pressure is still the most dominant feature of NZ and Australia’s weather going into June but the biggest changes (from a Big Picture point of view) may be more low pressure zones south of Australia (but still maybe not for those in the southeast of Aussie) and some life in the sub-tropics off the coast of Queensland and directly north of NZ in the tropics itself, around Vanuatu, New Caledonia and up to the Solomons.
Until NZ and Australia can shake these powerful high pressure zones, stuck mostly around Victoria and Tasmania, we may still notice a lot of May’s weather carrying on into June.
High pressure also means lighter winds – and that can mean colder nights. A calm, dry, high-pressure zone generally makes for colder nights and milder days, whereas a windy southerly or sou’wester can suppress daytime maximums but significantly lift up overnight lows.
Upcoming highlights:
• Frosts mostly confined to the interior and higher elevations parts of NZ, especially the South Island
• May’s final week looks chilly with sou’westers
• June might kick off with more high pressure
