Tropical cyclone season to hit a bit earlier, BoM predicts
The end of the El Nino and a negative Indian Ocean Dipole hint at an earlier start to the cyclone seasonThe Bureau of Meteorology has hinted at a higher than average chance of tropical cyclones arriving earlier than normal between now and April next year as it hands down its latest long-term predictions.
According to the bureau, eastern and northern Australia faces an increased risk of widespread flooding as we head into the part of the year where the nation enters its peak period for bushfires, heatwaves, flooding, tropical cyclones, and severe thunderstorms.
This was also likely to result in large surf, strong currents and debris washing into lakes and being swept offshore, creating collision hazards. There is also an increased likelihood of severe storms.
The bureau said the El Nino that was influencing Australia had stopped, with cooling of the tropical Pacific towards La Nina levels likely in the coming months.
“This may be increasing the chances of above-average rainfall for much of eastern and northern Australia,” it said.
“The negative Indian Ocean Dipole has weakened, but the residual pattern in the Indian Ocean typically favours above-average rainfall for parts of Australia.”
The chance of a La Nina forming was double the normal likelihood of the event occurring.
In terms of tropical cyclones, October 1 was the official start to the northern wet season.
Warmer waters
According to the bureau, generally warmer-than-average waters around northern Australia meant the region is likely to favour above-average humidity and rainfall in the coming months, and an earlier onset of the monsoon.
Combined with the negative Indian Ocean Dipole, this would increase the likelihood of an early tropical cyclone forming in the Australian region.
“Based on eight previous negative IOD events, the first cyclone of the season typically forms about three weeks earlier than normal – around mid-November compared to early December,” the bureau said.
“If La Nina forms, the probability of average to above-average tropical cyclone numbers during the 2021–22 season (November to April) increases.
“During La Nina years, rainfall totals across the duration of the wet season are typically above the long-term average for northern Australia.”
The Bureau of Meteorology updates its tropical forecast once a fortnight.
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