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New airflow but similar wind direction as Antarctic blast retreats offshore

The Antarctic portion of the winter storm feeding into New Zealand has now moved eastwards, off the mainland and out over the Chatham Islands – where it will soon also clear. Whilst NZ still has a big windy south-west airflow, the air feeding into it shifts from being partially Antarctic to now coming out of Australia and south of Australia.

Put simply – it’s like turning off the ‘freezing cold’ tap and turning on the ‘kinda cold’ tap.

This means the air temperature, for this time of year, may actually be a little milder than it might normally be – especially after a cold blast. Of course, Antarctic airflows into NZ don’t usually linger more than a few days and this one is being kicked eastwards by a more powerful westerly flow between the big storm in the Southern Ocean and a strong high over Australia. At we often refer to this as a “squash zone” – a mostly straight line of windy gales which will blow over NZ tonight and across Tuesday (easing slowly) keeping temperatures up for many and the frosts away overnight for most. The airflow direction will be west to south-west.

Monday may feel a bit like a spring or autumn pattern for some people, especially when the weather shifts so fast from a wintry blast to a windier, slightly milder set-up. But for those further south (and east for a time) the air will remain colder for longer this week, with airflows being dredged up from further south over the icy Southern Ocean.

NZ usually experiences peak winter cold over July and August, and sometimes the first half of September (mainly southern NZ). June this year, like April, was much warmer than average and’s latest ClimateWatch update out today for July suggests the milder theme will still likely dominate in the weeks ahead despite these occasional wintry blasts.

Despite the wintry weather on Sunday, Monday has normal to above normal temperatures everywhere but the heart of Central of Otago.
Windy weather with airflows out of Australia means tonight won’t be colder than average for everyone, only the east from about Christchurch to East Cape. All other parts of NZ are about normal, or even a tad warmer than usual for this time of year.
Over the past 24 hours the blue arrows (indicating cold air from Antarctica and the ice shelf) have shifted eastwards and now slightly milder air from Australia and near Tasmania is crossing the country. Wind map courtesy as of 4pm Monday.


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