Wednesday, 3 June 2020

BOM data for autumn is in and Australia has come out looking warm.

Bright red, yellow and orange autumn leaves
It may have been chilly in parts, but Australia was above average in autumn overall.(Supplied: Cassandra Brennan)
It might be hard to believe, considering how cold it has been in recent weeks, but autumn temperatures were actually slightly above average for Australia as a whole.
If you are in New South Wales, Victoria or Tasmania, though, you do have reason to moan — your mean temperatures were below average, although still only the 49th, 48th and 56th coldest on record since 1910.
NSW's days were particularly cold at 0.88 degrees Celsius below average, the 16th coldest average maximum temperature on record for the state.
The only jurisdiction close to a warm record was Western Australia, which recorded its ninth warmest mean temperature for autumn.
A blue boathouse in the middle of a river with its jetty underwater.
Perth's Insta-famous blue boathouse was inundated during a storm on May 25.(ABC News: Jessica Warriner)
Greg Browning, climatologist with the Bureau of Meteorology, said March and April were actually quite warm.
"April, in particular, was very warm across the country, but then we saw a significant drop-off come May," he said.
"So that was a real dampener on those warmer temperatures and really was a bit of a sudden shift towards winter conditions."
Map of Australia orange and yellow indicating above average in the north and west. Blue indicating below in inland NSW, VIC +SA.
Temperatures may have been above average overall, but it was chilly for parts of the south-east.(Supplied: BOM)

What is average?

The above-average temperatures are less of a surprise considering the BOM uses data from 1961 to 1990 to form the average for these comparisons.
This period is used as an international meteorological standard — a long dataset that formed a baseline to which people were accustomed, Mr Browning said.Metal fence with hexagonal  holes filled with ice crystals.
Some places were still frosty during autumn, as evidenced by Lake Saint Clair in Tasmania.(Supplied: Maren Gorne)
While some applications had started using 1981 to 2010 as the comparison period, he added, it had not filtered down to public products at this stage.
"Certainly based on the recent global warming that we've seen on the land and over the oceans, you would expect it to be significantly warmer than what we saw back in the 1960s and even 1990s."

Year so far and season to come

Australia is tracking for its 10th highest year to date for mean temperatures at 0.8 degrees above the 1961-to-1990 average.
Rainfall is pretty much bang on average according to Mr Browning, sitting at 1 per cent above average.
Raindrops on glass window.
There are still strong odds for a wetter-than-average winter.(ABC News: Chris Gillette)
"It's been a while since Australia has seen a significant period of above-average rainfall," he said.
"It certainly has been a big change in rainfall compared to recent years in particular."
Not all locations have received rain and some areas are still facing serious deficits after years of drought, however things are looking up on the whole.
The optimism continues when you look at the outlook, which suggests most of the country has at least a good chance of average or wetter-than-average conditions over winter.

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