Some towns in the state experienced four times the usual rainfall as the La Nina weather event took hold, the Bureau of Meteorology records show
NSW has experienced its wettest November since at least 1900, with some inland regions recording as much as four times the usual rainfall as the La Nina event in the Pacific took hold.
The Bureau of Meteorology, which will later today release more details on last month and the spring for the entire country, said a range of towns from Bathurst to Forbes beat previous rainfall records by a fifth.
Averaged across NSW, rainfall last month was 132.04mm, topping the previous record of just over 120.19mm set in 1917. It was also Australia’s wettest November, with an average of 72.62mm, beating the previous record of 70.14mm set in 1973.
Australia recorded its coolest November since 1999.
For the spring overall, rainfall in NSW and Australia was the most since 2010. Mean temperatures were the coolest since 2016.
The record rainfall comes as many rivers in the state have a flood watch in place, with more rain on the way. Over the next week, places in the north east can expect falls of 50mm or more, the bureau said.
“It was a combination [of] cloud cover and and we also saw just some cool outbreaks” during November, Agata Imielska, manager for the bureau’s NSW and ACT operations, said. With the background warming from climate change “these days are more unusual to what we generally see”, she said.
Australia’s weather has been favouring wetter-than-normal conditions since the drought broke in early 2020. Back to back La Nina events, the second of which was declared by the bureau last week, point to another relatively damp and cool summer ahead for eastern Australia.
During La Ninas, east to west winds blowing across the tropical Pacific strengthen, pushing rainfall westwards to Australia and south-east Asia.
Given catchments are already wet across most of central and eastern Australia, it won’t take much rain to trigger more floods. “It’s absolutely primed for flooding,” Imielska said.
Among inland towns, Bathurst broke its 113 years of records, with about 241.6mm of rain falling in its gauges. Forbes, which was flooded in part during November when the Lachlan River swelled, had 172.6mm.
Other parts of Australia were particularly wet, including South Australia, which posted its wettest November on record.
Victoria had 50% more rain than usual for the month, while the Murray Darling Basin as a whole tripled the usual rain, beating the previous record set in 1924. Western Australia, too, had almost twice the typical rain for November.
For spring as a whole, NSW had its fourth wettest September-November period, with about two-third more rain than usual, while Victoria’s tally was up about one-quarter. Nationally, it was the 10th wettest spring on record, with 57% more rain than usual.
Andrew Watkins, head of climate prediction services at the bureau, said the wet November in particular set up “massively different conditions” compared with a year ago even though the La Nina event itself is a weaker one than 12 months earlier.
November 2020 was unusually dry, while this year, “the soil is wet, the rivers are full and the dams are brimming”, Watkins said. As a result, it won’t take much more rain to have a big effect in terms of flooding, with many parts of the country already sodden.
This story was amended on 1 December 2021. An earlier version stated November was the coolest on record for NSW when it was the coolest since 1999.