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VIDEO: Significant rain possible for NI + Spring equinox & Daylight Saving

Over 200mm may fall in just the next 4 days for parts of the north eastern North Island as well as heavy rain moving up the South Island today. The two are connected but an area of low pressure deepening north of Bay of Plenty this weekend will add more rain into places like eastern BoP, Gisborne region and northern Hawke’s Bay.

Slips and flooding are possible in the North Island as a result of this rain – which will stall due to being trapped between two powerful highs, but being fed tropical air to keep the moisture levels up.

However next week a southerly flow dominates NZ with a colder Tuesday and Wednesday. By the end of next week, more high pressure from out of Australia returns.

With El Nino now here rain events like this usually become less common in the east – so make the most of it. Hopefully it’s not too much of a good thing though, with a fairly high risk of slips and localised flooding in both main islands of NZ (mostly the north-east of the North Island) over the next four days.

CORRECTION: When talking about the equinox, Phil mistakenly said something along the lines of “as the earth continues to tilt” our days get longer. This is incorrect as the earth’s tilt never changes. But that tilt + earth’s rotation around the sun means our days get longer as the northern hemisphere gets shorter. We’ll try to explain better in the next video! 🙂 More info here though:

Around September 22-23 is usually the Equinox – in this illustration it’s showing the Northern Hemisphere’s “Autumnal” Equinox which for us in New Zealand is the “Spring Equinox”. The earth’s tilt means that as earth rotates around the sun over 365 days we get our amazing shift in seasons. If earth didn’t have that permanent tilt then as we circled the sun there would be minimal temperature and rainfall change all year round and pretty much no seasons.

*Please note – Rainfall totals are not yet locked in. Keep up to date with MetService warnings and watches over the days ahead.


Derek Butcher on 23/09/2023 12:18am

An excellent forecast Phil, very informative, and great presentation.

WW Forecast Team on 23/09/2023 2:01am

Thanks very much Derek!

Mark on 22/09/2023 5:48am

Hi Phil what is the likelihood that Papamoa is in the firing line of this rain event?

Shane on 22/09/2023 4:25am

Any chance this could result in Auckland seeing flooding similar to January? Would be nice to prepare in advance this time, as I had water coming to the door, and got locked on my street due to flooding on one side of the road, while development blocked the other side. Really don’t want to repeat that panic. ☹️

WW Forecast Team on 22/09/2023 4:30am

Hi Shane, at this stage it looks like it will be lining up more to the east of Auckland. While it does have some similarities to Jan 27, it’s not a carbon copy and also has a number of differences. At this stage it’s more of a concern for eastern Bay of Plenty but other regions around Auckland (and maybe Auckland) might get heavy rain too. The Auckland event was a stalled thunderstorm – this event is a trapped rain band (wedged between two highs). We’ll be monitoring closely over the coming hours. Our rainfall data updates hourly and you can DOUBLE your local totals for the highest risk downpours in your region.
– Cheers WW

– WW

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