La Nina's wetter, cooler summer conditions likely created a buffer to cattle losses in the massive flooding event in the Gulf Country early this year, compared to the devastation of the 2019 event.
A comparison of the meteorological conditions of the two flooding events by Tim Cowan, from the University of Southern Queensland's Centre for Applied Climate, shows the 2023 event was less extreme in terms of cattle exposure.
Both events, the 2019 one occurring in February and this year's in March, came from slow-moving tropical depressions.
Speaking at the Northern Beef Research Update Conference in Darwin in August, Dr Cowan said analysing the two events in comparison to each other could provide valuable insights, given the possibility of monsoonal depressions over northern Australia occurring more often in coming decades.
During the 2019 event, extreme rainfall and high winds, along with cold temperatures, resulted in chill conditions that caused cattle hypothermia, he said.
The livestock losses were half a million head.
In 2019, Winton experienced five consecutive days of the cattle comfort index being below an extreme threshold, with values that would be considered severe for southern Australian sheep in the middle of winter, Dr Cowan reported.
Record-breaking rainfall and flooding this year was just as monumental.
In fact, for this year's event the highest daily accumulated rainfall was 313 millimetres, which fell at Century Mine on the Northern Territory Queensland border; while in 2019 the highest was 230mm, which fell at Julia Creek.
Ten-day total rainfall amounts were similar, with some locations exceeding 750mm, Dr Cowan said.
Daytime temperatures in both events were between 8 and 12 degrees Celsius colder than normal at that time of the year. They were in the 20s, where mid to low 30s would be considered normal for that time.
However, the 2023 flood event was less extreme in terms of cattle exposure. Losses were estimated in the vicinity of 50,000 head.
Dr Cowan said this was likely due to the preceding cooler and wetter weather - conditions typical under La Nina - which allowed livestock to better acclimatise.
"It is likely the higher loss of livestock in the 2019 event was due to the record breaking heat in the three months prior to the floods followed by the sharp drop in temperature due to the evaporative cooling after the rain," he said.
Cloncurry had a stretch of 43 days in a row of above 40 degrees Celsius in the lead-up to the 2019 event.
"Cattle in a weakened state would be unable to acclimatise to the cold temperatures within a week," Dr Cowan said.
"In contrast, months of wet and cool conditions in early 2023 meant livestock were able to better cope with the exposure to chill."
Another interesting insight from Dr Cowan's work was that while the Bureau of Meteorology predicted a 20 to 30 per cent likelihood of extreme conditions for the Gulf for the two weeks prior to the 2019 event, it struggled to forecast the 2023 event.
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