Weather watch: Thunderstruck

The weekend's rough weather in the North Island definitely marked a major turning point in our weather - this is just the start of wetter things to come.

It is unusual just how long this low has affected us. Starting last Saturday, 9 days ago, and still has at least 2 more days in it. The low is dancing around its own centre but is now weakening and falling apart.

On Friday and Saturday it created thousands of lightning strikes including a violent thunderstorm in Taranaki (one of many) that created a damaging tornado. The next day in Auckland another violent thunderstorm caused surface flooding, blew down trees, uplifted roofing tiles and also created a tornado. I received a few complaints at WeatherWatch about the use of the word "violent" describing it as dramatic and over the top when none of the weather stations they had looked at showed anything more than a heavy downpour and a few rumbles of thunder.

This is a very good point.

We often rely on weather stations to accurately report the weather to us - but as most Aucklanders know the weather in one suburb can be different in another and with only a handful of weather stations over Auckland it's not an accurate representation for all. Where I live, in west Auckland, it was definitely violent...with forked lightning nearly hitting a tree next to my house and cloud build ups that were borderline to creating tornadoes. Further north and a tornado did form. It flattened large trees and caused damage to buildings.

This is the one major problem for Auckland...one forecast often doesn't do the region justice. We get complaints after every storm saying we, or MetService, got it wrong - simply because nothing happened at their house. When you consider it takes over and hour to drive the length of Auckland you start to appreciate what a large area the city covers.

Vote in our Poll - how did you rate the weekend's thunderstorms?

This brings me to another point. Isolated. One thing that came from this storm was just how isolated the thunderstorms were. While over 10,000 strikes were detected by our lightning tracker on Saturday the thunderstorms mainly affected New Plymouth, Auckland and some parts of Northland.

A huge thunderstorm in the early hours of Saturday out in the Hauraki Gulf moved towards Bay of Plenty but missed Tauranga.

It was a perfect looking storm on the satellite map but it was patchy, and to be honest, a bit of a challenge for forecasters to get the wording bang on.

So now what?

Well our friend (who delivered much needed water all over the North Island's drought regions) is going to weaken, cross the country and leave via the Pacific Ocean in the next couple of days. Then we're in for a breather with a high moving in across the South Island.

But guess what? Another low - perhaps even bigger and more aggressive - is now being picked by the computer models. Not all of them are agreeing but between this high in the South Island and the departing low from the Tasman there'll be a bit of vacuum... and that could suck a low down from the Queensland coast. From that area it will have energy, moisture and warmth. Something to keep a very close eye on, now that Autumn's weather has finally arrived... just two weeks shy of the official start to winter.