A powerful storm over the Southern Ocean will propel gigantic waves to crash onto New Zealand shores on Thursday, creating "dangerous beach conditions".
Weatherwatch warns the weather over the sea south of New Zealand looks like the "depths of winter" due to the "power, size and depth" of a low there.
"This storm has air pressure down into the 940s hectopascal range today. To give you perspective, Hurricane Laura in late August this year was the strongest hurricane on record to make landfall in Louisiana. At its lowest point at sea, this hurricane dropped down to 937hPa."
The storm's centre is closer to Antarctica than Aotearoa and won't get any closer than it is on Thursday, but that doesn't mean Kiwis in the south won't see coastal areas lashed.
Waves of more than 12 metres are expected south of Stewart Island, while those hitting the south-west corner of Fiordland National Park will reach up 10 metres in height. Waves of up to 9 metres are possible in Southland, 3 to 5 metres waves are likely on the West Coast and 3 to 4 metres waves are possible later in the day on the Otago Peninsula.
"The Southern Ocean storm makes for more windy weather today and more lows next week will keep the westerlies blowing longer across New Zealand," said Weatherwatch.
It says there will be "dangerous beach conditions" in Southland, the West Coast and coastal Otago.
The West Coast and Catnerbury are likely to be buffeted by westerlies on Thursday with showers possible in southern parts. Southland and Otago will get up to 19C, West Coast could hit 16C and Canterbury may see 22C.
On Monday, NIWA released its seasonal climate outlook for summer, forecasting above average temperatures, elevated humidity levels, and other patterns consistent with moderate La Niña conditions.
"Although patterns of higher than normal pressure and drier conditions are expected to start summer, moist, sub-tropical disturbances are expected to reach the country occasionally, particularly the North Island and northern South Island. These systems can cause areas of heavy rainfall and flooding."
