Dry city of Hobart

It is perhaps surprising that the states with Australia’s two driest capital cities, being Tasmania (Hobart) and South Australia (Adelaide), were experiencing the least number of bushfires as Australian heat records fell in late December 2019.

However, when the fires started outside of Adelaide they moved fast. (EDIT: By December 23 in South Australia 86 homes were confirmed lost along with 404 other buildings and 227 vehicles over a weekend, with fires still burning. In the same period in NSW, 789 homes had been lost, with 40 in Queensland, and one in WA).

South Australia had 42C+ temperatures across much of the state on December 19.

Tasmania, though much cooler, is a dry state. Descriptions as “the second wettest state after Victoria” aren’t helpful, because very few people live on the rugged West Coast and high country where most of Tasmania’s rain falls.

The north, south, east and midlands of Tasmania are dry country.

Likewise, in northern mainland Australia, Darwin ranks No.1 for annual rainfall, but almost all of that falls during the wet season monsoon, with very little rain experienced during during the aptly named dry season (winter).

The historical averages of rain data for Australian capital cities, taken from 1981 to 2010, give these results.

On Tasmania’s West Coast, Strahan gets around 1742mm annually.

Outside of Darwin, Sydney and Brisbane otherwise rank as the two Aussie capital cities with the highest annual rainfall.

Sydney is fire central in 2019, presumably because it is surrounded by forest, and the forest is bone dry.

With climate change, rainfall patterns can change without being reflected in annual regional totals.

For example, in southern Tasmania the historic consecutive days (or weeks) of winter drizzle seem to be disappearing, but annual rainfall figures are maintained by short, heavy downpours in spring.

Such changes can significantly change soil hydrology, as heavy rain can run off dry ground, whereas days of drizzle tends to soak in.

The days of Tasmanian farmers trudging through boggy paddocks in gumboots may be over, except on the West Coast, and even there the trend has been towards less rain.

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