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| Tropical weather hit southern Victoria late last year. |
Melbourne's tropical weather late last year broke
records for humidity and short-term rainfall, according a special state
of the climate report released by the Bureau of Meteorology (BOM).
Victoria's capital was hit by sweltering conditions and severe storms on December 29 last year, damaging houses and prompting the rescue of more than 40 motorists trapped on flooded roads.Senior climatologist at the BOM Blair Trewin said the rare weather event was caused by tropical air from the Northern Territory, combining with remnants of a cyclone off the West Australian coast.
Not since 1982 have Victorians experienced a night like it, he said.
"We saw a number of places set records for humidity, including Melbourne, and also records for the greatest moisture content in the atmosphere," he said.
"The rainfall intensities we saw on the afternoon of the 29th, were pretty exceptional by Victorian standards - we had a fall of 40 millimetres in 15 minutes at Viewbank at the peak of the storm.
"That's up there with the highest rainfalls on record in Victoria for such a short timeframe, so it was definitely one of the most intense short term rainfalls that we've seen in Victoria."
The dew point temperature, a moisture measure which indicates what temperature air must be cooled to for dew to form, on December 29 was 24C.
Rivers burst their banks at the height of the rain, later causing Port Phillip Bay beaches to be closed due to faecal contamination from waste run-off.
Effect of climate change inconclusive
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| Storm clouds gather over Melbourne before a deluge. (ABC: Ben Lisson) |
With the release of annual statement, Climate Information Services assistant director Neil Plummer said 2016 was one of extreme weather events.
"We had our warmest autumn on record partly due to a very strong 2015-16 El Nino," he said.
"Widespread, drought-breaking rains led to flooding in multiple states. Even northern Australia saw widespread rainfall, during what is usually the dry season, greening regions that had been in drought for several years."
Globally, 2016 was the hottest year on record by a wide margin, European Union's Copernicus Climate Change Service found in a report also released last week.
But Mr Trewin said it was too early to tell whether Victoria's latest tropical turn was directly linked to climate change.
The last time a tropical weather pattern like December's reached as far south as Victoria was in 2011, following floods in Queensland, though it did not reach Melbourne.
Mr Trewin said two events in five years were not enough to draw a definitive conclusion.
"We do know that as the atmosphere warms one of consequences of that is that warmer air is capable of holding more moisture," he said.
"So there are good reasons why we would expect that we would get more events with extreme humidity of this type, but the number of cases we have so far is probably too small for us to be able to conclude that we're already observing a significant trend.
"What you'd be looking for is a sustained trend over a period of a number of decades — the nature of isolated extreme events because they are relatively rare, even if there is a real trend underlying it, it takes a while before we've actually got statistically convincing evidence of that."
Mr Trewin said despite the brief tropical conditions, he doubted Victorians planning to retire north for the warmer weather would be abandoning their plans just yet.
"I suspect that Victorians thinking of retiring to Queensland are thinking more about the winter than what it's doing in the summer," he said.As far as the outlook for the rest of summer, Victorians can expect it to be as dry and warm as usual.
"The best indication is that it will end up coming in reasonably close to normal," Mr Trewin said.
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| Brighton Beach-goers seek shelter as heavy rains sweep across Melbourne. (Fairfax Media: Penny Stephens) |
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