Archive for April, 2017

A precursor to winter

April 30, 2017

A trough of low pressure moved southeastwards over the country overnight Saturday, and lay southwest of the Chatham Islands Sunday morning. This system brought significant amounts of rain to much of the North Island during Saturday and into Sunday morning. In the 24 hours leading up to midday Sunday Stratford in Taranaki recorded 57mm, several stations in the Tararua Ranges recorded between 60 and 70mm, with one station in the Tararuas recording a total of 122mm. Parts of the Bay of Plenty also received significant rain, with many stations seeing around 50mm, but over the eastern Bay of Plenty ranges, one station (Haparapara) recorded 175mm in 24hrs.

The rain-bearing front all but cleared the North Island around midday today, but a cold front moving up the South Island spreads a very cold airmass over the country from the Southern Ocean. This front brings a cold, southerly outbreak to most of New Zealand during today and Monday, lowering temperatures and bringing gale force cold southerlies to many places. MetService has issued a Severe Weather Watch for Southerly Gales spreading north from Bank Peninsula to coastal Gisborne today and early Monday.

“There is a touch of winter around today and overnight for higher parts of the South Island and the central North Island” MetService Meteorologist Andy Best said. “Road Snowfall warnings have been issued by MetService for the Lewis Pass, Arthur’s Pass and Porters Pass.” Snow also gradually lowering to 900 metres for a time this evening in Nelson Lakes National Park, to around 800 metres today for Marlborough and the Canterbury Plains and to 700 metres in Central Otago and Southland. Over the North Island, snow lowering to 900 metres for a time overnight Sunday and early Monday over Egmont and Tongariro National Parks, as well as the Tararua and Ruahine Ranges. With the building of a ridge of high pressure over much of the South Island from Monday, clear skies and light winds are a recipe for light frosts around sunrise Tuesday in many inland sheltered parts of Southland, Otago and the Canterbury Plains.

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

MetService issues Warnings, Watches and Outlooks for severe weather over New Zealand.

Warnings are about taking action when severe weather is imminent or is occurring. They are issued only when required.
Recommendation: ACT 

Watches are about being alert when severe weather is possible, but not sufficiently imminent or certain for a Warning to be issued. They are issued only when required.
Recommendation: BE READY 

Outlooks are about looking ahead, providing advance information on possible future Watches and/or Warnings. They are issued routinely once or twice a day.
Recommendation: PLAN