The Bureau of Meteorology has warned of possible spring and summer flooding for south-eastern Australia, including Tasmania, after confirming that a La Nina event is occurring in the Pacific Ocean.
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It is the first time the event has occurred since 2010-12, which resulted in the wettest two years on record for Australia causing widespread flooding and severe tropical cyclones.
BOM first issued a La Nina alert in August, which was upgraded to an "active event" on Tuesday.
Bureau manager of climate operations Andrew Watkins said the country's south-east could expect increased rainfall for the remainder of the year, and the start of 2021.
What is La Nina? Video explainer:
"During La Nina, south-eastern Australia typically gets more rainfall during spring and also into the summer months as well," he said.
"This can wet up the soils and make the chance of widespread flooding and also at times flash flooding - the risk of those flooding events is higher during a La Nina event.
"Typically, more rainfall, wetter soils, higher rivers, more water going into our storages as well which is a good thing in many areas but also increases the risk of flooding."
About half of the BOM models predict a strong La Nina event, but it is not predicted to be as strong as eight years ago.
Check out pictures from the last time Launceston suffered extensive flooding, in winter 2016:
The cyclic event forms when strong equatorial winds draw up cooler water from the eastern and central Pacific Ocean. Recent observations show that the central tropical Pacific Ocean is 0.8 degrees Celsius cooler than normal, resulting in changes to trade wins and pressure patterns.
BOM modelling for Tasmania shows that the Tamar Valley and North East could cop the brunt of the wet weather from October to December.
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While flooding is always a risk during La Nina, Dr Watkins said it would almost certainly result in a mild bushfire season.
"In terms of bushfires and heat waves, luckily it reduces the risk of getting those really extreme heat waves, but unfortunately the heat waves we do get tend to be longer in duration and could be more humid as well," he said.
"In terms of fires, reduces the fire risk a little, but of course south eastern Australia - one of the most fire prone places in the world - we're not going to get through a summer without seeing any fires."
Launceston last experienced extensive flooding in June, 2016 - the largest since 1969.