It's a La Niña summer so Be Flood Ready

It's a La Niña summer so Be Flood Ready

1/12/21, 4:54 am

What is La Niña?

La Niña is part of a natural cycle known as the El Niño-Southern Oscillation (ENSO), which is a vast oceanic and atmospheric cycle that stretches over the Pacific Ocean; shaping weather globally, as well as in Australia.

It is the colder counterpart of El Niño, the hotter part of the cycle and its namesake.

On 23 November 2021, The Bureau of Meteorology (BoM) declared a La Niña was underway.

How did it get its name?

In the 17th century, South American fishermen first noticed periods of unusually warm water in the Pacific Ocean they called it El Niño de Navidad, or ‘Christ Child’ in Spanish, as the temperatures usually peaked in December. La Niña represents the ‘negative phase’ of a cycle which lasts anywhere from two to seven years.

What does this mean for our weather?

Eastern Australia is likely to be wetter than average, with an increased risk of tropical cyclones, heavy rainfall and widespread flooding.

Why?

La Niña occurs when equatorial trade winds become stronger, changing ocean surface currents and drawing cooler deep water up from below. This results in a cooling of the central and eastern tropical Pacific Ocean.

What does warmer surface water in the ocean have to do with the weather on land?

The enhanced trade winds also help to pile up warm surface waters in the western Pacific, where the warmer ocean temperatures mean the area becomes more favourable for rising air. Air rising in the west and descending in the east enhances an atmospheric circulation – called the Walker circulation – which can result in changes to the climate felt across the globe.

When the Walker circulation is especially strong, this causes La Niña!

Didn’t this happen last year?

This is the second year in a row La Niña has been declared. The last time Australia experienced a ‘double-dip’ La Niña was summer 2010/11, which had devastating consequences from riverine flooding right across Victoria.

How is VICSES preparing?

VICSES is preparing for what could be a very wet Summer.

Our catchments are already wet in some parts of the state , particularly in Gippsland and the North East. We know a significant flood event is the last thing Victorians need as they emerge from lockdown, but we need you to prepare for the possibility. The last significant La Niña event was 2010 - 2011 which had devastating consequences from riverine flooding right across Victoria.

How can I be flood ready?

There are so many things you can do:

-  Understand the local flood history in your suburb or township by downloading your Local Flood Guide (LFG). With your LFG you can get to know your local risk profile, potential impact areas and how floodwater usually behaves in your local area.

-  Never drive on flooded roads. The main cause of death during a flood event is caused when people attempting to drive through floodwater. It can take just 15cm of water to cause a small car to float. That’s the length of a pen, so it’s not much. Stay safe: never enter floodwater.

-  ‘Bag It, Block It Lift It and Leave’, if your home is being threatened by major flooding:

i. Bag it - by laying sandbags where water may get into your home.

ii. Block it - by covering your toilet and drains to prevent back-flow

iii. ’Lift-it and Leave’ by shifting valuables onto tables and benchtops and leaving early, to a family or friends house on higher ground.

- Stay informed by monitoring forecasts, river levels and weather warnings at the Bureau of Meteorology website - bom.gov.au

- Like all emergencies we encourage community members to download the Vic Emergency App and set up a watch zone to ensure they receive community notifications and warnings.

- Never wait for a warning to act. You may not always receive an official warning.

Quotes attributable to Chief Officer Operations, Tim Wiebusch:

"As we enter our second La Niña summer - with catchments wetter and water storages fuller than in 2020 - along with our experience last year we know Victorians are at increased risk from flooding."
 
"That's why I'm asking you to download your Local Flood Guide, available from our website, so you understand how floodwater behaves if it reaches your local area."
 
"If you're intending to camp alongside a river, be mindful that riverine flooding can change the landscape around you significantly. Localised heavy rainfall means there isn't always an official warning before this happens."
 
"Most of all, please don't drive through floodwater, it may be the last decision you make. Even if you think you know the road, you can't see the extent to which it has been washed away. It only takes 15cm of floodwater to cause a car to lose traction, which sadly is how most people lose their lives during a flood."

Quotes attributable to Head of Operational Climate Services, Bureau of Meteorology, Dr Andrew Watkins:

“Spring has been wetter than normal and, as a result, soil moisture is high, water storages are full, and we've seen flooding in some areas. Any additional rain on our already wet landscape will increase the flood risk for eastern Australia this summer.”

"December is likely to see our typical summer weather systems pushed further south than normal, meaning more humid air coming off the Tasman Sea, and into NSW and eastern Victoria.”