Weather turns into a typical Autumn pattern

The Indian Summer has come to an end as the weather around New Zealand finally shifts into a more typical Autumn pattern. Temperatures across the country were very low on Saturday with most places struggling to get over 12 degrees - including Auckland.

The high in Auckland was 12 however most places spent the day on 10 or 11 with light non-stop rain. I have to admit that our forecasts weren't accurate leading up to Saturday. It wasn't until Friday evening that we realised a pool of unstable air over Auckland combined with a rapidly deepening low north east of Northland meant rain would set in.

We have a "we got it wrong" policy in which we're open about why we get certain forecasts wrong. While weather forecasting is far from being 100 per cent accurate you can't help but feel terrible when you get a forecast wrong - especially a Saturday forecast when everyone's relying on it. For those in the upper north of New Zealand you can see how fine the line was with forecasting this weekend - Saturday was cold, grey and wet - Sunday was blue skies and even hot in the sun. Such a stark contrast.

I lit my fire for the first time on Saturday - so to me winter has now officially started! (I'm a fan of longer summers, longer winters and short autumns and springs). Of course I'm talking about an Auckland winter... in which it rarely drops below zero at night and rarely falls below the teens as our official high.

A friend of mine from Taupo reminded me to toughen up on Saturday when I complained that it was only 12 in Auckland.... She pointed out - 1 in Taupo that morning. I lived 2 years in Taupo a decade ago and to this day I can still feel that wind howling off the snow covered mountains, across the lake and straight into my apartment on the waterfront. She's right - I've softened since moving to Auckland.

To my cousins who live in Toronto, where it's minus 40 in the depths of winter, they think it's incredible that in northern New Zealand flowers bloom, lawns need mowing and you can sit outside on a sunny, calm, winters day in shorts and a t-shirt. In fact, there are even places in the South Island where that's possible too. I think our climate is fantastic in this country - we get a good mix of everything.

The low that formed near the Northland coast deepened very quickly across the weekend and is now quite a significant storm east of New Zealand. This storm missed us but did deliver heavy rain to Gisborne - so thumbs up there, it's just what the farmers needed.

South Islanders along the southern and eastern coastlines managed to gain a few degrees across the weekend compared to last week. This week is unsettled and the potential is there for a storm this weekend. The air pressure around New Zealand will slowly drop this week - the lower the air the more unstable the atmosphere is.

Think of the atmosphere's air pressure like the pressure in your car tyre - when the tyre is flat the car is much harder to drive - dangerous too. Low air pressure allows storms to erupt and much bigger rain clouds to form.

Some long range models show a very deep low over central New Zealand on Saturday and with it the potential for heavy rain in the west, warm nor'westers in the north and east, then turning to a bitterly cold southerly with gales and possibly snow to lowish levels in the South Island and heavy showers everywhere else.

It's still a number of days out but we'll be monitoring it closely that's for sure. May is usually when we start to see these winter storms creeping up - and it's really just a matter of weeks before we get our first southerly blast. I measure a good winter storm by how far north the snow falls - usually snow on the Desert Road is a good indicator. A particularly strong winter storm usually leaves snow on the ranges of the Coromandel Peninsula and to sea level in Christchurch.

So we'll see where this one goes - we have a low and its associated fronts moving up the country during Tuesday starting early in the south and reaching northern places later in the day. Strong winds will follow. This is perhaps only just a taste of what the next low will bring.

Philip Duncan

Photo / Te Puke Times