Spring has sprung - sort of

BY PAUL GORMAN - SCIENCE REPORTER

LATEST: Don't be fooled by the sunshine and that hint of warmth - temperatures are about to plummet.

After Christchurch's truly miserable  August, whose 86.7 hours of sun came within an hour of setting a new record for the least sunshine, you could be forgiven for thinking spring is really here.

But while the daffodils, the lambs and the daylight hours point to it being spring, the weather is about to plunge us into the depths of winter.

An active cold front barrelling across the Tasman Sea today will bring a spell of rain and strong winds to Canterbury tomorrow before temperatures fall in the evening as southerlies develop.

After a clearance on Friday morning, very cold south-westerlies will freshen in the afternoon with showers likely and snow to low levels.

The cold blast is expected to be over by early Saturday morning, but MetService is warning snow will affect the passes before the weather clears.

Warm Spring expected

The National Institute of Water and Atmospheric Research (Niwa) predicts temperatures in coastal Canterbury will ``very likely'' be above average over the next three months, while rainfall is expected to be about normal.

The strength of La Nina - which typically brings mild, damp north-easterly winds and sub-tropical low pressure systems towards the east coast of both islands - was moderate at the moment but could continue intensifying throughout the rest of the year, making those conditions more likely.

Principal climate scientist Dr James Renwick said there was a ``pretty good chance'' La Nina would get stronger.

``It's looking pretty solid. It is not going to get derailed now, that's for sure. I think we should see some pretty clear effects over the next few months.

``Usually they peak about December-January and a classic La Nina event would start to fade in February and be all gone by May.''

Unfortunately for Canterbury residents the phenomenon was always at its strongest over summer, so its effects were most noticeable then too, Renwick said.

``But it's quite good in terms of temperature, for the growing season, we get this warm spring, which is good for grass growth.''

Niwa and MetService scientists were going to meet soon to talk about La Nina's potential impact on the track of tropical cyclones later in the summer, he said.

- © Fairfax NZ News