The early spring pattern is very much locked in across New Zealand with westerlies dominating, pushing temperatures above normal by day and by night over most parts of both islands.

We do have a couple of cold fronts this week which will help make for more average temperatures at times, especially for those in the west. These milder westerly quarter winds will keep frosts away, or if they do form inland they will be very light and mainly around Central Otago and the South Island high country.  Frosts are unlikely in the North Island in the week ahead but a high brushing the North Island this coming Saturday may make for clear skies and light winds and encourage light frosts around Central Plateau…although Waiouru at 800m above sea level only has a low of +1 this Saturday, so frosts look light.

The westerly quarter winds kick in from this Tuesday through until Friday/Saturday when they somewhat fade back thanks to a high brushing northern regions.

So where is our next big southerly?

August has so far been seen much milder than usual weather across New Zealand heralding an early start to spring. There have been no major southerlies so far this month but long range models for over a week now have been indicating that a southerly is possible in the second half of the month. Latest computer model guidance today still shows the chance of a polar southerly next week – but it is not locked in due to the chaotic weather flow around it.

At this early stage there is the chance for a cold, wintry, southerly arriving late next Monday (Aug 20th) and peaking on Tuesday/Wednesday nationwide. There is a lot of uncertainty locking this in though, as the high just west of NZ (which will help encourage the coldest part of this southerly) looks quite unreliable to lock in.

The shape of this high will determine how cold and far reaching any southerly might be over New Zealand and based on computer models right now this high could very easily morph into a milder westerly system (like all the others this month) or strengthen into a much more polar southerly around one week from now. For now it’s one to just keep an eye on. 

– Image / Air pressure and rain map for next Wednesday (Aug 22) showing a possible cold south to south west change / GFS (US Govt)

– WeatherWatch.co.nz