A large low is developing around NZ this week and weekend - but it’s going to be spinning like a lopsided washing machine with a load making it spin off kilter. It means it’s a very messy forecast - one that will change further in the coming days as the centre of the low moves around a lot and changes shape. This shifts and even reduces severe risks for now.
Why so much uncertainty? Both the shape of the low and the precise location of the centre can't yet be locked in by usually reliable modelling. This is due to the precarious nature of the southerly and northerly feeds going into it - and the high pressure zone near Tasmania that could sneak in south of it all and then shut down the southerly feed.
The low may even start to push itself back towards Australia for a time - which significantly reduces severe weather risks in NZ…but then may well come back bringing another burst of rain or showers.
But the low pressure centre creates instability - and that makes this a very tricky system to be precise with, especially on Friday as rain moves further across the country.
For now, this low doesn’t look as severe as it did a few days ago - but is likely to linger with us for a week at least and so severe weather may still be in the forecast from tonight through until Wednesday of next week.