Dangerous Waves for New Year’s Day

As 2017 ticks to a close most of the weather and wave action will be happening on the western side of the country, and the trend continues into 2018. Large swells are expected to build on Mondayalong the western shoreline, also most of the rain affecting New Zealand is coming in from the Tasman Sea, with heavy falls in the west.

A Southern Ocean swell is forecast to arrive along the west coast during New Year’s Day. Long period swell waves will begin to arrive late tonight in the South Island and early tomorrow in the North Island. A rapid increase in wave height is expected, and marine users are urged to be aware of the changing conditions.

“Previous holiday seasons have had tragedies occur in rising conditions like this”, said oceanographer Dr Peter McComb. “Not only are the swell waves forecast to become 2 or 3 times larger over the course of the day, we are likely to see the sudden arrival of groups of big waves, which can take people by surprise.”

People planning a west coast swim on New Year’s Day are advised to find a patrolled beach, and that rock ledge fishing and bar crossing by boat may become hazardous. Surfers however, will be delighted by this first swell of 2018, which is forecast to provide very good surfing conditions. Significant wave heights of up to 3 metres and at 14 second peak period are predicted for Tuesday, easing to around 2 metres for Wednesday through Saturday.

Unlike the distant origins of the swell, local weather conditions are being driven by a tongue of humid air which stretches over the country from the Tasman Sea. This means heavy rain in the west of the South Island – with 134mm recorded at Milford Sound airport between 11am Saturday and 11amSunday - and showers developing during New Year’s Eve for western parts of the North Island. Eastern and inland areas of the North Island should stay dry, although a southerly will bring brief rain to eastern parts of the South Island. Wanaka will see a few afternoon showers, but this should clear in the evening leaving dry weather for the changing of the year at Rhythm and Alps.

The warm tongue sticks around through the first week of 2018, bringing further rain to the west and a few thunderstorms to the Central North Island particularly on Tuesday. Towards the end of the week a significant low will develop on the tongue and track across the North Island, which is expected to bring significant rain with it.

Official Severe Weather Watches and Warnings are reviewed and re-issued by MetService at least every twelve hours, and more often if necessary. To get the most up to date information on severe weather around the country, or any other forecasts, see metservice.com or on mobile devices at m.metservice.com. You can also follow our updates on MetService TV, at MetService New Zealand on Facebook, @metservice and @MetServiceWARN on Twitter and at blog.metservice.com

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