September 2022 Mallacoota Weather Report

 I am tempted to start with "Same old, same old" or "Here we go again" as the weather shows the same major attributes as it has for most of the last three years.  Warm nights and rather damp!  I should probably modify that slightly by adding "Ending up with ...." as until about 21 September the anomaly was lurking in the red and rainfall was well below expectations.  From then on every overnight minimum was above average and we had rain on 8 of the last 9 days.

The August weather report included "In terms of human behaviour we have not had a fire for the last 5 days on August and have turned the booster off on our hot water: solar is doing the job."  The hot water booster has been on for the last 10 days: the need for this is shown by the BoM cloud cover ratings from Gabo being 7 or 8 (8 being the maximum) for 12 of the 20 readings.  I also lit the fire in the lounge in the evening of the 30th to escape the dreariness rather than it being very cold.

Rainfall

This ended up being 80.8 mm for the month (107% of mean and 123% of median).  It was a little less than recorded in September 2021.

The concentration of the fall in the last 10 days is shown clearly in the next chart, which also shows how moderate the daily falls were, with a maximum of 11.4mm on the 29th.

None of the falls were particularly intense: the maximum rate of rain was 72.4 mm mid-morning on the 30th, which is an underwhelming 36th heaviest rate I have recorded here.  

My prorata estimate of the annual fall has been holding fairly steady for about the last three months.  Given the forecast of La Nina for the future that seems like a fair guess.  

Should we achieve the estimate of 1375 mm for the year that would be about the 3rd highest fall since records began in 1975 (with a few incomplete years in the early 1980s).

I have also examined the number of raindays in Septembers since 1975.  (Most of these data come from BoM and in earlier times - presumably when data was compiled manually - it is common for days to be combined, or missed completely.  Where that is obvious I have omitted the record from this series.)

Clearly a very variable item, with 2022 in the upper part of the range.

Temperatures

The anomaly (difference to long term mean) ended at +0.38C, with a balance between warm minima (+1.3C over the month) and cool maxima (-0.5C over the month).  The next image shows the development of the anomaly through the month.

Another general comment on the weather is the daily extremes.  

The two current series for BoM data show quite clearly how the anomaly developed.  Comparing the current BoM series with those for my WS is interesting:

• for the Maximum series the lines are almost overlaid until the 25th, when for three days my WS records much higher.  I believe this is due to cloud from the sea reducing the maximum of the BoM series.
• the Minimum series has more significant differences.  I suspect (but cannot prove as BoM do not present the time of minimum temperatures) this reflects the BoM series resetting at 0900 while my WS follows the more far rational approach of resetting at midnight.  

Minimum temperatures

The average minimum temperature recorded by my WS was 9.77C. This is the second highest recorded, although there have been several over the years which exceed 9.5C.  

I have plotted the time series of monthly average minima for the 4 years we have been at Mallacoota.  It shows recent months this year as warmer (less cold?) than other years sfter a period in which all years were very similar..

Maximum temperatures

The average Maximum temperature of 17.27C was among the coldest recorded for Mallacoota.  It was well below 2021 and the long term average.

Looking at the 4 years from my WS shows this year to be very much on the low side.

Humidity

Basically a very damp month, with the lowest humidity at either of the standard times being 57%.  It was particularly noticeable that the 15:00 hrs readings were high relative to those of 09:00 hours.  (Note that the cropped vertical axis exaggerates the unusual values.)

The above changes are shown in the charts for 0900 and 1500 hrs below,  

The comparison of these periods for the BoM site are not so pronounced, but still show 2022 as more humid than 2021.