Extreme weather over last few days

It's been a stormy few days across the country as a wintry blast moved over us. Here's a quick look back at some of the extremes:

Culverden's high on Wednesday: Just 6 degrees.

Kaikoura on Tuesday night: Winds averaging 90km/h with gusts close to 130km/h

North Otago: Snow falls.

Auckland: Gales off and on during Wednesday with gusts up to 90km/h in exposed places.

Christchurch: Temperature dropped 12 degrees in just 14 minutes as the front came through. From 24 to 12 degrees in less than quarter of an hour.

My colleague in Christchurch, weather analyst Richard Green, took these two dramatic photos as hot and sunny weather turned to an ominous, wintry, gale. Pic 1. Pic 2. They are spectacular photos.

This storm was just one of the recent weekly storms over the past month. This was the first polar one - the other 3 have been from the sub-tropics. So, how's this weekend looking? Well, mostly sunny and settled across the country...but it's not going to be perfect for everyone, namely Auckland and Northland.

The high that's moving in is the large one that blocked now ex-tropical cyclone Hamish from coming our way... it's also half of the reason why we've had strong to gale force sou'westers for the past two days (the other half of the equation was a very deep low in the Southern Ocean pushing against that high). This anticyclone will now spread a ridge over the country during Friday and by Saturday should dominate most of the nation's weather.

In the north there is a slight problem but it starts with something further south - the centre of the high. The centre should cross the central South Island on Saturday. That means the top of the high, where the winds blow easterly, will be over the northern tip of the North Island - from about Auckland and northern Coromandel northwards.

Easterlies like this can often produce showers or light rain. For those who were married on Valentines Day last month you were most likely surprised (probably disappointed) to find rain had set in when you woke up after weather forecasts the day before (including ours) said it would be a mostly sunny day, just a few early showers clearing. This particular weather setup in Auckland makes forecasting a headache...it's very hard to predict when it will arrive...and even when it's around it can be hard to work out when it will leave. Auckland usually gets this weather a couple of times of year.

The Coromandel Peninsula and wind direction play a big part in it too. If the wind is south-easterly the Coromandel blocks the rain clouds from moving to Auckland. When the easterly has more of a northerly tilt to it the rain clouds can feed straight in through the gulf, mostly affecting places between the CBD and Hibiscus Coast.

We'll be tracking the rain clouds on Saturday - you can keep up to date with our new and independent weather forecasts for Auckland which you'll find here. At this stage the winds look south east (dry) but may produce some showers later in the day when it turns more easterly.

Back to the rest of New Zealand - this high will be moving through quite quickly. We are approaching the Autumn Equinox afterall so highs and lows should be scooting through fast. Gales and heavy showers from the Tasman Sea are also likely.

With these highs constantly moving in from Tasmania we're also likely to see more of these south westerly winds over the coming weeks - and maybe an ex-tropical cyclone or more sub-tropical lows thanks to the warmer waters north of New Zealand (La Nina). If that high hadn't have been in the Tasman Sea I'm pretty confident cyclone Hamish would've wound up on our northern doorstep with a tropical deluge.

So this high will move through quite quickly and behind it is our next Autumnal (there's that word again) low. This low is likely to move in from the southern Tasman Sea on Monday or Tuesday and bring a period of warm, strong, nor'westers to the South Island and maybe lower North Island. This will be followed, of course, by the usual sou'west change although it doesn't look likely to be another polar blast.

Sou'westers look in order for much of next week too, but probably not as strong as this week.

To sum up, next week looks a little ho-hum. To some that's a bit boring, to others that's great news.

Philip Duncan

Photo / Sarah Ivey