A very large area of low pressure is forming in the Tasman Sea and is going to bring heavy rain to western and northern parts of New Zealand on Thursday according to WeatherWatch.co.nz.

Latest weather charts, produced by government forecaster MetService, show the system will have five centres as of 1 o’clock Thursday morning with the entire centre of the system stretching from Tasmania to well east of Otago.

Head weather analyst Philip Duncan says while the extra large size doesn’t mean it will be more severe, it does indicate a number of unsettled days ahead.

“Larger systems are often less aggressive but tend to bring more days of unsettled weather.  This will take several days to cross the country and with it will come warm nor’westers, heavy rain and thunderstorms”.

Mr Duncan says unlike a smaller, more aggressive, low this system will have several fronts which will circle around it.  “It’s like a conveyor belt of fronts moving around it so we can expect rain, showers and sunny spells too from Wednesday right through until as late as Wednesday next week – a seven day low”.

According to long range weather maps used by WeatherWatch.co.nz the centre of the low will slowly drift north east towards the North Island on Monday then a cooler sou’west change will move in after it. 

Until then most of New Zealand will enjoy much warmer weather thanks to winds from the northerly quarter.

MetService has high to moderate confidence of rain warnings for western parts of the country on Thursday and Friday, warnings will most likely be issued.