How dry is it?

On the Mallacoota Community Facebook group a few members have been asking questions along the lines of "Why is this year different in terms of fire risk?".  Robin Bryant has answered this by quoting the CFA assessment (emphasis added):

The CFA assessment of 16 December is ... The outlook suggests that above-normal bushfire activity will continue across the coastal and foothill areas of East and West Gippsland, across to the Great Dividing Range, however this now extends west to also includes the Central Goldfields, which takes in parts of the Wimmera and Mallee.

This is due to above average temperatures drying out grasslands and forests over the last three months coupled with three years of significant rainfall deficit in much of East Gippsland and across the Divide. While there has been spring rain in the south, much of inland Victoria received insufficient rainfall and as a result, soil moisture is lower compared to the long-term average.

When grasses and crops are close to fully dry, there is a very high potential for fire behavior to rapidly escalate under elevated fire weather conditions.

I thought it worthwhile illustrating the rainfall deficit.  These data are from the BoM site out near the airport, beginning with the annual totals (I have assumed that we are going to get no more rain in the last three days of December).

Its a pity that there are a few years missing, but such is life.  The decline in the last three years is very evident ending with 2019 being the lowest on record at 595 mm.  (There are only two other years below 700 mm.)

The missing years place difficulties in getting a 3 year series with a lot of observations but it is a good bit smoother than the annual data. This show a high plateau early on, followed by a lower plateau and then the drop-off in the last three years.

Further insights can be gained by looking at the data recorded by BoM for Timbillica, just across the NSW border. This typically has an orographic component to its falls as the air from coast rises as it meets the hills.  This site has very good data with only 1 year missing back to 1910.  (December data for 2019 is not yet available for this site so I have estimated it as 50% more than the December fall for Mallacoota.)  The annual values show a lot of variation and I have cut to the chase with triennial data.

The trend line is essentially flat due to variation over time.  However the three year total ending in 2019 is very low: only the years 1981-82 are lower.  So, again, this period is unusually dry.