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The Big Picture (3 graphics) – Current rain radar brings our graphics to life

The current wind flow around New Zealand relates to these graphics below. Check out the current MetService rain radar here, then compare to the graphics on this page. In the radar you can see how the mountains and ranges of New Zealand are helping shape the flow of the showers on both the western and eastern coastlines. The Southern Alps has the biggest impact, sheltering many South Island regions not to mention the majority of the North Island in this current set up.  However – if the winds change just slightly to the west or the south, it can cause a significant change to the flow of those showers – turning sunny weather into cloud and showers. Sometimes the difference between sun and showers can be the tiniest of changes to the wind flow.

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Original Story

It’s quite normal in New Zealand to have a wind flow that blows showers in one direction along one coastline – but along that coastline there are pockets of beautiful sunny weather where no showers fall.

Or how about that forecast that said “Sunny with southerlies” only to wake and find it’s cloudy with showers. How on earth could a forecaster get something so basic so very wrong?

Well the answer lies in our mountains and ranges – they stand tall into the sky and block many showers and cloudy areas…and a slight shift in the general wind flow (and we really do mean a *slight* shift) can have significant consequences to the weather where you are.

In the graphics below the blue shading indicates showery areas – the yellow indicates the regions most likely to remain dry in that wind flow. 

You can also see how a slight shift in wind direction – say a SouthWest wind that turns slightly more Southerly – can drive showers into a very large part of the country while giving others glorious sun.

The South West flow is probably the trickiest of all to nail down – it’s our most common wind direction and it runs parallel to both our western and eastern coastlines.  So it only has to tilt a tiny bit more westerly to make for wet weather in the east and dry in the south…or tilt a little southerly and do the complete opposite.


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