Storms possible in the south as wild weather arrives in the north

The Weather Service is warning of possible thunderstorms in parts of the south today, and more severe weather in the North Island.

Low-level humidity and a convergent sea breeze are expected to bring rain to some inland areas of the South Island later today, the forecaster said.

There was a moderate risk of thunderstorms over Central Otago, East Otago and Dunedin, and northwards in Buller, Nelson/Tasman and the Canterbury High Country.

Storms can come with small hail and rainfall rates of up to 25 mm/hour.

Meanwhile, motorists are being urged to exercise caution on roads across the Upper North Island this afternoon and evening, amid possible severe thunderstorms that could bring locally heavy rainfall of up to 45mm/hour.

Meteorology warned of severe thunderstorms in some northern areas until eight in the evening, with the possibility of heavy rain and hail in some areas.

In parts of Auckland, Waikato, Coromandel and the Bay of Plenty west of Rotorua, there was a high risk of thunderstorm activity – and a moderate risk that could be severe, with rainfall rates from 25mm/hour to 45mm/hour.

Across the wider affected areas, the MetService was giving a moderate risk of thunderstorms from Northland, down to Waitomo and across the western Bay of Plenty during the afternoon and into the evening.

These storms could come with heavy rain of up to 10mm/h to 25mm/h and hail – and there was also a low risk of small tornadoes or funnel clouds, especially between Northland and Waitomo.

The forecast came with continued moisture from a slow-moving front combined with daytime heating and cold temperatures in the upper levels over New Zealand.

“Almost the majority of the northern half of the North Island is at risk of seeing some heavy rain today – all linked to an old low hanging over the north-east,” MetService meteorologist Louis Ferris said.

Conditions were already very wet in areas – the dew point exceeded 20°C at Auckland Airport today – and direct sunlight this afternoon could cause the surface to warm quickly, creating thunderstorm conditions.

“People will definitely see growing clouds this afternoon, and if they’re unlucky, they could get caught in one of the heavy rain showers, or maybe even thunderstorms,” Ferris said.

“If it’s already raining where you’re driving, it’s just a matter of slowing down and paying attention.”

Elsewhere, MetService reported a reduced risk of thunderstorms in other northern areas down to Taumarunui and Taupo, and across north of Gisborne.

Ferris encouraged people in areas potentially affected by the hurricane to monitor the forecast.

“The watch covers the potential for severe thunderstorms and if we notice one on our radar network we will issue a red severe thunderstorm warning, meaning impacts are likely and people should avoid the area if possible.”

Eastern parts of the North Island are likely to be affected by onshore winds until Wednesday, meaning overcast days with rain, more persistent on higher ground.

While the upper half of the North Island and the interior of the South Island are expected to see light winds and clear skies this week, during the afternoon, rain could fall, with the possibility of thunderstorms in the mix.

Warm temperatures were also on the menu in some places, with Christchurch expected to reach 26C on Thursday, about 6C warmer than the average daytime maximum for this time of year.

But Cantabrians will need to finish again on Friday, when an outbreak of cold air from the Southern Ocean drops that high to a forecast low of 14C.