KEY POINTS:
Life a figure skater spinning out on the ice - that's the analogy I'm using to describe this storm moving across the country at the moment.
You probably often hear terms like "organised" and "disorganised". Well this system is organised.
It has a centre to it with a large 'eye', it also - from space - looks like the perfect low pressure system with cloud swirling into it's centre. In fact the cloud is impressive, mixing with the sub-tropical jet stream yesterday north of New Zealand the cloud stretched from northern Australia right down over us and deep into the Southern Ocean.
In fact, in a rarely seen satellite image you couldn't see each end of the frontal cloud.
But the system is well organised and what that means is that it is pretty predictable and has a clear centre to it.
The figure skater analogy is this: when a skater spins on the ice they pull their arms in across their chest - as they do this, they spin faster. That's what this low is doing - the isobars are closely packed so the whole thing spins fast.
From the latest satellite maps you can see it's clearly developed eye. Now it's this eye that brings bitter sweet weather. The eye is calm - light winds, and often clear skies. All the severe weather spirals around the outer wall of the eye - sometimes hundreds of kilometres away from the centre. That's the sweet part.
The bitter part is that the eye is where the air pressure is at it's lowest. Simply put, when the air pressure is high it pushes the sea level down. When the air pressure is low that allows the sea to rise and create a storm surge. That coupled with gale force winds driving even more water in and suddenly exposed western beaches from the Kapiti Coast to Southern Taranaki are in an extremely dangerous situation. Beach erosion, huge waves several metres high, king tides, massive rips and coastal flooding are all a possibility today.
It's not too often we see such a clearly developed low pressure system so if you're a geek and you enjoy this stuff make sure you take a look at the satellite map at the Weather Watch Centre . If you click on it, it will animate for you and you'll see the low clearly in action along the West Coast.
One more thing to note with a system like this - they can be fatal. These storms are dangerous and while deaths in New Zealand related to the weather remain low that's partly because of our education on what to do (or not do) in severe weather. A lady had her leg broken in New Plymouth when a gust of wind blew her out into an oncoming vehicle yesterday. A man in the weekend was apparently blown across his room after his house was hit by lightning and he was listening to headphones on his computer. This nasty storm does pose a risk to life and property - so over the next 24 to 36 hours take extreme care and take note of what's happening around you weather-wise just to be safe.
Philip Duncan
For the latest weather news keep up to date with The Radio Network's new Weather Watch Centre or the NZ Herald weather section.
Pictured above: Cars are enveloped by a large wave crashing over Marine Drive. Photo / Mark Mitchell
