High Pressure Brings Coldest September Nights In 20, 50, 100 Years To Parts of Eastern Australia!

Written by on September 2, 2012 in Australasia with 0 Comments

It’s been a winter which will likely become known as one of the worst in many years from Alice Springs to the East Coast. Persistent high pressure systems and southerly air flows supported frequent spells of ‘worst cold nights’ in 20, 30, 40, 50+ years from southern Queensland all the way to Tasmania. We even saw record cold all the way to tropical Darwin. With strong Southern Ocean storms we’ve also seen decent rains and strong to gale-force winds along the Southeast and East coasts with lots of snow over the Alps of NSW. According to The Weather Channel based in Sydney, the snow season is considered best in at least 8-10 years.

These large, sprawling high pressure systems over eastern Australia have supported many glorious sunny, mild summer and now spring days but with a steady cold, southerly air flow blowing off the Southern Ocean has kept the mid-levels of the atmosphere very cold. After sunset, under clear, starry skies and light winds, this cold air suspended above a warm surface layer produced by daytime heating, begins to ascend down to the surface, eroding the warm layer, droping the suspended cold air down to the surface.

As you can see from today’s ECMWF chart, there is a large high still over eastern Australia and this will support another few cold, frosty nights.

Parts of New South Wales Start Sunday With Coldest September Night In 100 Years!

The most impressive lows this morning hit the town of Bourke where the low was -0.2C, doesn’t seem that cold right? That’s 9C below normal and the coldest September low in an amazing 104 years!

Canberra and Tamworth started off today at -5 and -4C respectively, that’s the coldest September night in 55 years for both cities! Mudgee hit -4.4C which was that towns coldest in over 50 years for Sept.

At Grafton Ap, the temperature fell 10C below normal to set their coldest Sept night in 46 years with a chilly 0.1C.

Across the typically chillier Ranges, the temperature plunged all the way to -9C at Cooma Airport, -8.6C at Thredbo Top Station, -8C at Glen Innes Airport were all the coldest Sept lows in this region in 15 years.

All stats courtesy of The Weather Channel Australia (@WeatherAUS)

This upper chart shows the low heights and cool 850 temps so while days are mild, those clear skies, light winds allow the cold air aloft to drop to the surface at night with any warmth at the surface escaping back to space.

Warmer Weather Is Coming This Week!

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