August 2023 Weather Report

 In summary, and for those in Mallacoota stating the obvious, hot - for the time of year - and very dry.  I shall go into more detail below, but the average temperature was 1.8C above the normal and the rainfall was the second lowest total for August.  Combining rainfall totals for July and August the period was the 4th lowest rainfall since my records began.

A common comment about weather forecasting is "Look out the window!".  In a similar vein, to assess the temperatures this season look at the wood heap.  We have in the past considered that we need 5 trailers of firewood for a Winter.  This year we have rarely lit the fire and probably only used one trailer-load (thus far at least - September is starting off cool).

Data Quality Note

My weather station delivered a dodgy record on the 1st of August.  This wasn't immediately obvious and in attempting to fix this I ended up trashing the data from 0900 on 1 August to 0600 on 5 August.  Thus there is a gap in some variables for that period.  Fortunately I had saved the rainfall and extreme daily temperatures in spreadsheets so the gap is not too serious (for this purpose).  I am mainly stating this as an aide-memoire in case I become perplexed about more detailed analysis later!

Rainfall

What is this thing called rain?  An advantage of very low totals is that trivial amounts, such as the 0.2mm due to a heavy dew, show up more obviously!

The usual comparative chart confirms the poor state of affairs!

The prorata estimate of expected annual rainfall is at 655 mm by the end of the month.  That would be the 2nd lowest annual total since my series began in 1975.  A chart showing the progress of this estimate gives a steady decline since the 9th of May: nearly 4 months.

Temperatures

The obvious overall indicator is the anomaly showing the difference between average temperature for the month and the long term mean for August.  For 2023 this resolves to +1.8C, which in the time series chart shows as the highest monthly value since November 2020.  The moving average (which cancels out seasonality) moves further away from the trend line.

For the month of August the early part of the month was very warm indeed (see discussion below) and after dropping briefly mid month, with the anomaly going below +1C, built up steadily again towards the end of the month.

A plot of daily extreme temperatures shows the same pattern.

Minimum Temperatures

It is tempting to ask "What is a minimum temperature?" with a month this warm.  The average minimum was 7.88C which is 1.5C above the long term mean.  Surprisingly, this average is below that for the last 2 years.

Looking at my time series of plots from my weather station puts this month's minimum in the middle of the pack.

In terms of extremes I note daily extreme reading that are significantly above or below the long term average for the month.  For this month there were 8 minima >1 Standard Deviation (SD) above the long term mean, and only 1 minimum >1SD below the long term mean.  Obviously, no cold spells (3 consecutive days with min and max > 1SD below the mean).

Maximum temperatures

The average maximum for August was 17.59C.  Although 1.85C above the long term mean (including an adjustment to improve comparability between my WS and the BoM Airport site) this is only the 4th highest average maximum for August: the highest August average (18.6C) was in 2009 while 2007 and 2013 both scored 17.8C.  

Looking at the series for my WS 2023 is well above other recent years (but as indicated in the preamble to this section well below some other years).

The counterpoint to Cold Spell is Heat Wave, which I define as 3 consecutive Hot Days (which are Days with both minimum and maximum more than 1 SD above the long term mean maximum for the month).  There were no Heat Waves in this month although the period 3rd-4th(close, but no cigar), 22nd and 29th were Hot Days.  Going further the minimum on the 4th and the maximum on the 4th and the 22nd were more than 2 SD above the mean.

Balancing those days, to a limited extent, were 3 days with maxima more than 1 SD below the long term mean.

Humidity

Both standard humidity readings were lower than 2022.  The reading for 0900hrs was less depressed than than for 1500hrs, which continued the situation of other months in this year of being significantly lower than for 2022.

Wind

The data from my weather shows it to have been a very calm month.  I haven't been able to confirm this from other sources, but have no memory of ferocious winds, so will believe the data!