Chaotic weather cancels flights, sparks flood worry

Monday, 2 December 2019

The West Coast and Wellington will live up to their wet and windy reputations this week.

Many Air New Zealand flights in and out of Wellington airport have been cancelled, with a bout ofchaotic weather due to hit the country.

At least eight flights departing from Wellington on Tuesday morning are cancelled, and nine arrivals.

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Air New Zealand has cancelled flights from Wellington airport on Tuesday.

While the airline wasn't offering cash refunds, it said customers with cancelled flights could transfer their booking to another date or hold the fare value in credit for up to 12 months toward future travel.

The same front was forecast to cause extreme weather events all around the country - but different regions would be affected in different ways.

Waiho Bridge was taken out by the flooded Waiho River in March.

* What killed the Westport rats?**

On the West Coast, rain began barrelling down overnight Monday, with fears it could cause flooding on a similar level to the storm that wiped out the Waiho bridge in March.

A heavy rain warning was in place for Westland through to midnight Tuesday, with up to 350mm of rain expected in the hills, peaking at around 40mm an hour.

River levels were high and the soil would not be able to absorb much more moisture, meaning flood risk is high.

In Wellington, Nelson, and the Canterbury high country warnings are in place for strong winds with gusts as high as 140kmh. MetService was warning of potential damage to trees and powerlines.

In the upper North Island, it was a very different story, with high temperatures and humidity. Gisborne would see temperatures of above 26 degrees Celsius for at least the next week.

All of those seemingly different weather phenomena were caused by the same front moving in from the west.

That's due to the Foehn effect. As the moist air makes contact with the western side of the Southern Alps, it triggers rainfall.

That means the air very dry by the time it moves over the mountains, so it is picking up more heat as it moves over to the west.

'It's the perfect set up for significant weather events… it ticks every box,' Metservice meteorologist Georgina Griffiths.

Griffiths said the most serious weather event was the heavy rain on the West Coast.

The flood risk would be 'comparable' to the storm that caused serious flooding event in March, which left one person dead.