Ex-tropical low : An upper North Island deluge

An epic deluge event over the upper North Island was a significant multi-day heavy rainfall episode driven by an ex-tropical low that approached from the north, combined with a strong, humid easterly to northeasterly flow. This brought prolonged, intense rain to already saturated ground, leading to widespread flooding, landslides, road closures, evacuations, and unfortunately a loss of life.

Here is a meteorological summary timeline of how the event unfolded.

11th Jan - A tropical low named 94P (14U BoM) developed over the Coral Sea, 450km west of the Vanuatu archipelago.

Tropical low 94P IR satellite image 11th January 2026

15th Jan - The super-ensemble mean made up of over 100+ model runs from EU, US, CA & UK started to trend the tropical low to be steered by a mid-latitude trough SE towards Norfolk Island with the next few days.

Super ensemble run showing a concerning trend for NZ

18th Jan - A low pressure trough developed over the upper North Island with a moisture link to tropical low 94P. This bought torrential run to eastern parts of Northland with overnight falls to near 200mm in some areas.

6:20am radar on 18th January

20th Jan - Tropical low 94P dropped to 988 hPa remaining just under tropical storm strength. The 5:40pm water vapour satellite image showed an immense amount of moisture being transported from the tropics in the airmass.

Water vapour image at 5;40pm with weather features

21st Jan - The water vapour image now showed the immense plume of mid level moisture now sinking over the North Island. The tropical low 94P commenced its convective subtropical transition phase. Energy is being sourced from the temperature differences between the surface and the cooling upper troposphere. Cold cloud tops were around -70°c on the eastern side of the low showing the deep convection being triggered by this phase. Heavy rain and winds were starting to ramp up across the upper North Island.

Water vapour image with position of ex-tropical low 94P

MetService upgraded warnings for Northland, Coromandel Peninsula and Bay of Plenty to the highest Red warning.

Concerning rainfall totals started appear on private gauges by mid afternoon on the eastern side of the Coromandel Peninsula.

News coverage on the unfolding rain event

22nd Jan - Incredible 48 hour rainfall totals were evident by 6am

Coromandel Peninsula

778mm - Pauanui : Sheppard ave (644mm 21st Jan)

682mm - Pauanui : Panorama pde (567mm 21st Jan)

630mm - Pauanui : Waterways pde (530mm 21st Jan)

Northland

328mm - Opua : Paihia rd

Auckland

235mm - Matakana: Awanui cres

Great Barrier Island

449mm - Claris airport

Waiheke Island

182mm - Onetangi : Marine view rd

Flooding and slips across Northland and the eastern side of the Coromandel Peninsula were widespread cutting townships off. Unfortunately 9 lives were lost including 6 at Mount Maunganui camping ground due to a slip.

24th Jan - Severe gales with heavy showers pounded the upper North Island with the low's backend.

MetService hand drawn map late on 24th January