Torrential localised downpours have flooded suburbs across Wellington with little warning.
Other areas across the North Island have also been affected, with more rain expected until Tuesday night.
The SMC asked experts to comment on flood warnings, cleaning up mould, climate change, and what weather is still to come.
Feel free to use these comments in your reporting or follow up with the contact details provided.
Dr Sally Potter, social scientist and warnings consultant, Director of Canary Innovation Ltd., comments:
“My thoughts are with anyone who has to clean up floodwater and silt following these severe weather events around the country. Having had to do this myself over the weekend with the localised downpours in Tauranga, I feel your pain.
“It is difficult for forecasters to know exactly where localised downpours, thunderstorms, and tornadoes will occur before they happen – the science just isn’t there yet. This means that we can’t get specific warnings for these events hours in advance. This is different to more broadscale events, such as Cyclone Vaianu, where days of warning can be given.
“What you can do is always store items that are important to you off the floor, and in watertight containers. Then if you are surprised by a flood, you have a better chance at keeping those items safe.
“You can keep an eye on the forecasts, particularly for words like ‘localised’, ‘thunderstorms’, and ‘downpours’. If these are in the mix, then they can occur anywhere in the area. They may hit you or someone else across the region, so it’s best to get prepared if you can, just in case. In these situations, you can do things like have your grab bag ready, park your car on higher ground if possible, lift rugs off the floor, and prepare for keeping your animals safe.
“There may only be time for natural warning signs, rather than official warnings. Remember to keep an eye out for any signs of landslides due to all this rain – things like small slips that can lead to bigger landslides, fences and walls tilting away, new cracks or bulges on the ground or retaining walls. If you see any of these signs, evacuate, and tell neighbours, emergency services, and your local council.”
Conflict of interest statement: “None.”
Dr Mikael Boulic, Senior Lecturer, School of Built Environment, Massey University, comments:
“Mould spores are everywhere; now that flooding has brought the water, the mould will need food to grow. Materials we find around our house, like wooden surfaces, paper and books, cardboard, curtains, and fabric, can be a good source of food for mould.
“The key sentence is “Dry as quick as possible to avoid mould from starting to grow!”
- Ventilate as much as possible,
- Use a dehumidifier (professional ones are much more powerful)
- Heaters could also help in drying out
“What to do if you spot mould patches? If you find some small mould patches, you can clean them with a solution of 70% white vinegar and 30% water instead of harsh chemicals. However, mould will return if moisture persists, so it’s crucial to eliminate dampness to solve the problem.
“If you have extensive mould patches, it is safe to ask advice from mould experts. Warm, dry and mould-free homes are crucial for your family’s well-being.”
Note: Dr Boulic and other experts have previously commented on making homes safe after flooding.
Conflict of interest statement: No declaration received.
James Renwick, Professor of Climate Science, Victoria University of Wellington, comments:
“The flooding in Wellington over the weekend is shocking in its intensity, so much damage and disruption happening so quickly, an absolute nightmare for those affected.
“The Mayor reported that 77 mm of rain fell in one hour at one location, a level of rainfall that is truly tropical and would be extreme even in the tropics.
“We are again seeing the effects of adding moisture to the air, which happens as that air warms. More moisture equals heavier rain, and can lead to more intense thunderstorms that draw in even more moisture to deliver the kind of deluges we saw this weekend.
“The only way to stop such events becoming more extreme is to stop adding greenhouse gases to the air, especially carbon dioxide from fossil fuel burning. Anything our government, and all governments, can do to move away from fossil energy is something we would all be thankful for.
“In the meantime, we must all adapt as best we can.”
Conflict of interest statement: “I have received government funding for climate change research, through MBIE and the Royal Society Te Aparangi.”
Dr Lauren Vinnell, Senior Lecturer of Emergency Management, Joint Centre for Disaster Research, Massey University, comments:
“It’s been a tough night for many Wellingtonians, with more rain on the way.
“Despite best efforts, there isn’t always time to get official warnings out and flooding can be very localised making it hard to predict where exactly it’ll happen.
“It’s important to keep an eye on your surroundings and if you think you’re in danger, act immediately. If you feel unsafe, arrange to stay with family or friends or head to an evacuation shelter. Landslides and floodwaters can be very dangerous, so stay away if you can. Download the Metservice app, listen to RNZ, and find your local emergency management group online to stay up-to-date.”
Conflict of interest statement: “No real or perceived conflicts of interest to declare.”
Lewis Ferris, Meteorologist, Metservice, comments:
“Our Severe Weather team have just sent a new issue of warnings:
“Heavy Rain Warning – Orange
- Area: The Tararua Range, Tararua District and Wairarapa
- Period: 39hrs from 9am Mon, 20 Apr – midnight Tue, 21 Apr
- Forecast: Heavy rain in South Wairarapa is expected to spread northwards this afternoon. Expect 80 to 120 mm to accumulate, but 150 to 250 mm about the ranges and coastal hills. Peak rates of 15 to 25 mm/h, but 25 to 40 mm/h possible in localised places, especially in thunderstorms. Moderate chance of upgrading to a Red Warning.
- Impact: Streams and rivers may rise rapidly. Surface flooding, slips, and difficult driving conditions possible.
- Action: Clear your drains and gutters to prepare for heavy rain. Avoid low-lying areas and drive cautiously. Preparedness advice here.
- Area: Wellington excluding Porirua
- Period: 36hrs from 9am Mon, 20 Apr – 9pm Tue, 21 Apr
- Forecast: Expect 50 to 80 mm but 100 to 150 mm about the eastern hills and Hutt Valley. These amounts are in addition to the rain that has already fallen. Peak rates of 15 to 25 mm/h but 25 to 40 mm/h possible in localised places until tonight, especially in thunderstorms. Moderate chance of upgrading to a Red Warning.
- Impact: Streams and rivers may rise rapidly. Surface flooding, slips, and difficult driving conditions possible.
- Action: Clear your drains and gutters to prepare for heavy rain. Avoid low-lying areas and drive cautiously. Preparedness advice here.
“Once we make it into Wednesday it just looks like a few lingering showers. After that, current data has a run of dry days which will be welcome news for those with cleanup to do.
Conflict of interest statement: No declaration received.