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: https://earthsky.org/tonight/equinox-sun-rises-due-east-and-sets-due-west

*Please note – Rainfall totals are not yet locked in. Keep up to date with MetService warnings and watches over the days ahead. https://www.weatherwatch.co.nz/maps-radars/warnings/metservice

Why the intense pockets of heavy rain? It's a classic #ConvergenceZone – A big southerly flow from the Southern Ocean meeting a strong northerly flow from the sub-tropics.

The two air flows become head-locked, keeping a line of heavy rain stuck in one area for a long time. pic.twitter.com/kGOEArju2l

— WeatherWatch.co.nz (@WeatherWatchNZ) September 23, 2023

🚨Early rain estimates for eastern #BayOfPlenty look significant this weekend. At sea level totals of 150 – 200mm over 3 days are possible. Totals in the hills & ranges may be 200mm – 300mm.

More details in our weather video & at https://t.co/D35ySCkVqG https://t.co/200TSjzxpn pic.twitter.com/iRaZXL5Ih5

— WeatherWatch.co.nz (@WeatherWatchNZ) September 22, 2023

🌀🌀It's a slow moving, complicated, system over the South Island. Here's what's going on as of 4:30pm Fri: Warm & humid air from #Tonga feeding down from the north, mixing over the SI with cold air off the #SouthernOcean.

🎥
🟢Rain / Showers
🟡Heavy Rain
🔵Snow
🟣Snow/Rain mix pic.twitter.com/Op1y92gaUV

— WeatherWatch.co.nz (@WeatherWatchNZ) September 22, 2023