Northland weather alert: Heavy downpours and thunderstorm watch in force

MetService is warning heavy downpours may be on the cards in Northland this afternoon. Photo / NZME

A severe thunderstorm watch has been issued for Northland as the wet weather continues into the weekend.

The watch issued by MetService covers from 3pm today until 9pm, with localised downpours of 25 to 40mm/h forecast for that six-hour period.

Heavy showers and thunderstorms were likely to be generated from a warm moist air-mass and daytime heating, MetService said.

“Rainfall of this intensity can cause surface and/or flash flooding, especially about low-lying areas such as streams, rivers or narrow valleys, and may also lead to slips.”

MetService meteorologist Katie Hillyer said places in Northland further east were most likely to be affected by today’s weather.

“The worst affected areas yesterday were inland Northland and a bit closer to the West Coast as well. Today, it’s a little bit more focused just right down the spine inland.”

The west coast of Northland yesterday experienced between 30mm and 60mm of rain in a six-hour span, as well as about 15 lightning strikes.

“Some of these places got around 30mm in an hour, which is a significant downpour and would have definitely led to areas of surface flooding,” Hillyer said.

“Very similar idea today with the severe thunderstorm watch that we have out for inland Northland and north Northern Auckland.”

“The risk really is for downpours, 25 to 40mm of rain per hour are possible.”

Hillyer said the risk of downpours or flash flooding was the real hazard compared to lightning strikes.

Today’s thunderstorms and heavy rain may linger over a location for a long period of time.

“Quite often we’ll have thunderstorms and heavy rain and downpours with fronts that move through an area but this is setting up in a convergence and can just sit over one location and so really drive up the rainfall in a very localised way,” Hillyer said.