Whilst the rapid poleward spread totalling about 800 kilometres (seven-and-a-but degrees of latitude) in the past fifty years of the winter Hadley cell is a key factor – and remember it is known that at Mesozoic and Paleegene CO2 levels of around 2,000 ppm there was no winter Ferrel Cell and hence no winter “storms” whatsoever – most of Victoria this May and July has not been so dry as Melbourne.
|March 2017 rainfall percentages|
|April 2017 rainfall percentages|
|May 2017 rainfall percentages|
This is very different from May 2003 (below) whereby – although there were some similarities within Victoria – the north and central coasts of New South Wales were wet and northwestern Tassie much drier:
|May 2003 rainfall percentages. Note the different patterns in Tasmania from last May.|
|June 1963 rainfall deciles (most precise figures to avoid the massive influence of Australian greenhouse gas emissions)|
|June 2017 rainfall percentages|
The daytime weather in Melbourne was a delightful 15˚C for the opening two weeks of June before we left for hot and humid Taipei – which I did not enjoy at all – but the nights were so cold as to virtually freeze my right hand in our poorly insulated plasterboard home when I sat at the computer until 01:00.
|July 2017 rainfall percentages|
The map is very much drier than remotely similar maps from before the Lonie Report. The famously windy September 1941 – probably the windiest month ever in most of southeastern Australia – is a good illustration:
|September 1941 rainfall deciles. These are a bit like last month shifted 800 to 900 kilometres (by removing Australian greenhouse gas emissions) equatorward|
So, if we place Melbourne near Bourke, one can almost imagine the dry, hot westerly winds New South Wales had in September 1941. These dry winds seen here in Melbourne would still be around Bourke if Australia had had a sane transport and energy policy for the past four decades!