A burst of cold air originating from the Antarctic ice sheet is expected to affect New Zealand on Monday and Tuesday. Unseasonably cold temperatures, strong winds and snow to low levels are expected over the South Island where this event is likely to have a high impact. Livestock could be affected and it will probably have an effect on higher roads where significant snow accumulations may make driving conditions difficult and could lead to some road closures. The coldest air is expected to make its way north to the North Island on Tuesday bringing strong winds and unusually low temperatures. For further details, please check forecasts for your specific location and keep up to date with watches and warnings issued on our website, www.metservice.com. Please keep safe and warm.

Expected surface temperatures at noon on Tuesday, lines every 5 degrees Celcius Expected surface temperatures at noon on Tuesday, lines every 5 degrees Celcius

 

The image above shows the expected surface temperature at noon on Tuesday, from Antarctica in the south where the air originated, north to New Zealand. The air over Antarctica is colder than -20C but it has warmed up over the sea on its way north. Over the South coast the lowest layer is at around 10C but the air is much colder inland over the South Island, below freezing above about 800 metres above sea level.

Wave height at noon on Tuesday, courtesy of ECMWF Wave height at noon on Tuesday, courtesy of ECMWF

In addition to the strong winds and cold temperatures on land, large south to southwest swells are expected to affect much of the New Zealand coastline on Monday and Tuesday. When the strong to gale southerly winds are combined with these swells, waves greater than 6 metres are likely – possibly reaching 8 to 10 metres along the east coast for a time on Tuesday. If you’re planning to head onto or near the water over the next few days, make sure you check out the latest marine forecasts and warnings on metservice.com