The Daily Examiner.

Thursday Update 9 am

• An ‘atmospheric river’ has started crashing over the top of the South Island.
• MetService says residents should prepare for flooding and slips in affected areas.
• The rain will mainly impact the South Island today with heavy rain watches in place for Tasman, Buller, Marlborough, Kaikōura and the Westland ranges.
• Heavy rain watches have also been issued for Auckland and Northland for this evening.

Fresh weather warnings have been issued for much of the North Island as an “atmospheric river” begins dumping 450mm of rain over the country.

Residents in the top of the South Island are being warned of possible flooding and slips with rain watches in place for the North Island.

More than 31 hours of rain is expected in many regions across the country.

MetService meteorologist Surprise Mhlongo said the rain had begun to soak the upper South Island overnight with 80mm of rain already washing over the Tasman region. The Tasman District Council was warning residents that slips and flooding could impact vital roads.

“Isolated heavy bursts are possible and could result in more significant flooding in small creeks and surface flooding. Expect some slipping to occur in prone areas.

“Rainfall is forecast to be highest toward the end of the event when catchments are soaked.”

Rainfall is expected to accumulate to 400mm today in the Tasman area which is equal to 400 litres per m2 – but what does this even mean?

MetService Meterologist Mmathapelo Makgabutlane said for context this rainfall “is similar to the amount that would fall throughout an entire month but it is in a day and a half” in the Kahurangi Ranges. 

Makgabutlane said the heaviest bulk of the rain is expected in the ranges, with large amounts to reach 450mm. 

“Away from ranges we could still see amounts of 150-250mm of rain, if that amount falls in Nelson that is over double of its monthly rainfall in a day and a half.”

Nelson’s average monthly rainfall in April is 68mm.