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Special Update: Explosive cyclogenesis to create Antarctic blast

A ‘weather bomb’ is likely to form this weekend, that’s a rapidly deepening low that will see the central air pressure plummet from around 980hPa on Saturday to 930hPa on Monday.

The low itself is NOT going over the top of NZ but it will grow so large over the Southern Ocean it will bring strong winds, snow and sub zero wind chills to parts of the lower South Island and gales may spread as far north as Auckland City.

Meanwhile other northern and eastern areas aren’t so badly impacted. We have full details for the weekend and next week until Wednesday.

To drill down deeper, visit NZ’s largest weather data website at


Graeme on 26/09/2020 6:22am

Hi Phil,

Great video about the developing weather system.

Is there any possibility you could put together a video on what the drivers are that create this sort of storm and why the air pressure drops so low so fast?

All the best. WW is great viewing!

WW Forecast Team on 26/09/2020 7:37am

Thanks Graeme,
Probably don’t have the time/resources to do a video just for that but basically it’s in a unique position with the jet stream (higher altitude winds) acting to help spin this low fast – it’s also dropping into an area of low pressure (a low moving into a low!) and that helps make it rapidly grow. It’s a unique set up where it’s given a push out of Australia and it moves into the ideal area to spin fast…like when you spin a coin on a table and nail it perfectly and it spins super fast in one spot. Hope that helps 🙂
Philip Duncan

p.s Wikipedia has some good info on it too:

Andrew on 24/09/2020 11:30pm

Such a pity we had ponderous, weak, subtropical depressions over winter rather than this.
Given it’s nearly October we should get more moister but any action is so short lived.
Tomato seedling sellers rejoice! You’ll get to sell them all over again next weekend!

Deb on 25/09/2020 6:11am

Oh I laughed about the seedlings! So true 🙂

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