By Chris Oldfield
RECENT flash flooding in Naracoorte was the result of a new two-day rainfall record, according to the Bureau of Meteorology.
The official two-day rainfall total in the 48 hours to 9am on November 25 was 117.8 mm.
“(It) is not only a new November record, but also an annual record in the bureau observations at Naracoorte – current and former site – since 1884,” a spokesperson told The News.
“The previous annual record two-day total was 108mm on 6-7 March, 1910, at the former station.”
In the 24 hours from 9am November 24 to 9am the following day the bureau’s rain gauge at Naracoorte aerodrome recorded 71.4mm.
“Most of this rainfall occurred with thunderstorms between 5pm and 7pm Friday,” the spokesperson said.
“The intensity of the rainfall saw 44.6mm of this rainfall recorded in 30 minutes, 48mm recorded in 1 hour and 68.6mm in 2 hours.
“This observation site has been operational since 1998. The 71.4mm recorded is an annual highest daily rainfall record for the current station at Naracoorte since 1998.
“The previous annual record was 69.4mm on January 14, 2011.
“The previous November daily record for the current station was from the day before, November 24, 2023, when 46.4mm was recorded.”
From 140 years of daily data, the previous November rainfall record was 52.2mm, on November 29, 1977.
The highest daily amount ever recorded at Naracoorte was 85.6mm on April 23, 1913.
Many private rain gauges in Naracoorte recorded varying amounts between 40-50mm, then 70-100mm after that.
Several people have also offered their figures to The News showing they received between 150 and 180 mm.
“Thunderstorms are often isolated in nature which means rainfall can vary widely from region to region, town to town, even suburb to suburb,” the spokesperson said.
“Furthermore, the bureau has strict criteria for the siting of our observation equipment, which private rain gauges may not adhere to.”
The spokesperson believed many rainfall totals were consistent with those recorded by the bureau with 46.4 in the 24 hours to 9am on Friday, November 24, and 71.4 to 9am the following day.
“Thunderstorms that formed on Friday (November 24) were due to a broad surface trough and low,” the spokesperson said.
“The passage of troughs and lows is not uncommon for this time of year, however this system moved in from the east, which is a bit unusual.”
