Often when we predict a cold change we usually expect it to sweep up the country and go from warm to cold in a matter of hours or a day or two max.
This weekend a low pressure system will intensify as it pushes off Australia’s eastern coastline – with a cold change coming behind it when the winds swing south to south west. However at the same time this low moves east across the Tasman Sea this weekend a bubble of high pressure will zip in south of it – in effect, cutting off the southerly flow for a few days.
“Cold air will affect some southern and eastern areas – but as the Aussie low moves closer towards New Zealand this high in the south will race in first across the South Island, then zip up the east coast of New Zealand , to end up in front of the low, by early next week” says head weather analyst Philip Duncan.
“Once the high is then east of New Zealand it will slow down the Aussie low in the Tasman and therefore slow down the southerly flow behind it. It’s a bit like being overtaken by a truck on the flat but it then holds you up on the first hill”.
This means Sunday will see rain clouds building across most of western and northern New Zealand but weather temperatures in the north will remain warm and well above average.
The low will take a few days to now cross the country because of this blocking high – with a long lasting and colder south to south west flow moving across the nation later next week and potentially lasting for several days nationwide.
on 12/06/2013 9:17pm
Unfortunately this high cant be stuck over new zealand or just east of it,funny it is stuck in the tasman,races over the country then stuck so far east the next one affects us in the tasman.
on 12/06/2013 8:24pm
Interesting that Metservice have rain for Saturday but looking at maps I agree with you. They seem to over forecast in most cases.