The sub-tropical low which has stalled over Northland will tomorrow help create a secondary low north of the country which will then rapidly cross the upper North Island on Wednesday night bringing torrential rain and possible gales.

WeatherWatch.co.nz says the type of rain band moving in will be different to Monday’s slow moving one – instead this one is likely to rocket across the upper North Island in about 12 hours – with the worst of the wind and rain likely withing 6 hours.  It’s likely to then slow down but weaken.

“This secondary low will be small but sharp and could bring in a period of torrential rain and gusty to gale force nor’easters from Bay of Plenty northwards” says head weather analyst Philip Duncan.

“There is potential for slips and flash flooding with this next spell of severe weather along with isolated power cuts due to slips or small branches taking out powerlines”.

By dawn Thursday this new low will be lying over Taranaki and by noon it will die out over the upper South Island – bringing in some wind and rain to most parts of the North Island and upper South Island at some stage.

“These lows are acting like cogs by working together to pull down moisture rich sub-tropical air”.

Mr Duncan says by Friday the nation will have a breather before a Southern Ocean low churns by south of New Zealand bringing a change to strong westerlies.

– WeatherWatch.co.nz