September 2024 Weather report

 Overall a rather temperate month: somewhat like Baby Bear's porridge in avoiding extremes!

Rainfall

After a dry August (36% of median fall) the rainfall improved to 89% of median (64.2 mm) in September, which is well above last year.

 As a result we are now 330 mm above last year's fall to date and my prorata estimate of the annual fall for 2024 is now 1055 mm.  The development of the prorata estimate since March shows that it has been fairly flat over September (as one would expect with a close to median fall).

Temperatures

The overall value of the anomaly ended the month at -0.07C which I regard as effectively zero.  The development of the anomaly shows a hot start to the month with a steady cooling later.  (We lit the fire on a few evenings late in the month.)  The last third of the month was a value constantly just below 0C.

A time series of values of the anomaly shows it as beginning to head downwards although the trend of the moving average is still upwards.

A chart of the daily extremes shows the warm start to the month followed by some low temperatures and the end of the month quite close to average.  (Note that the averages are now limited to the period since 2019 and only show the values from my weather station.)  There were 3 warm days (both extremes significantly above the monthly average) but not consecutive so no heatwave and 2 cold days (both extremes significantly below the monthly average)

The fluctuations in the average series did cause me to explore the pattern of variability between months and to my surprise September temperatures overall were not as variable as those for July and August.

Minimum Temperatures

The average minimum temperature was 9.03C, with a range from 4.1C to 14.6C.  The lowest value was the 3rd lowest recorded in September at home while the highest was the 6th highest.    In total there were 4 days significantly of low minima and 4 with significantly high minima: not all of these coincided with high maxima.

The set of monthly minima since 2019 show this year to be in the middle of the bunch.

Maximum Temperatures

The average maximum temperature was 18.7C, with a range from 11.8C to 30.6C.  The lowest value, on the 14th, was the lowest maximum recorded in September at home (and the second lowest this year - 12.2C was the second lowest at home).  The value of 11.8 was still the lowest if the values from the BoM back to 1995 were included.  The highest was the 2nd highest at home, but only the 6th highest if the Airport values are included (the highest 2 values were both over 34C.

By coincidence, in total there were 4 days significantly of low maxima and 4 with significantly high maxima: not all of these coincided with high maxima.

The average maximum was above average but below 2023.

Looking at the time series for home 2024 is (again) in the middle of the range.

Humidity

The daily humidities at standard times present a strange picture.  

• The first unusual feature is the very low readings early in the month: these would have been low reading at the relatively inland site we used to live in near Canberra.
• Secondly the closeness of the morning and afternoon values; and
• Finally the high level of variation, especially in the morning series.

The morning series is a little below average but above 2023.

The afternoon series is a little above mean and a lot above 2023.

Wind

The daily wind run shows three periods in brisk winds.

The longest run, 228km on the 2nd was the 12th longest September run (of 180 I have recorded) so of interest but not exceptional.  The longest run in September at home was 519km on the 20th in 2019 (and the second longest, of 363 km, occurred on the next day).

Overall the breezes showed the expected pick up after a calm couple of months over Winter.  The average run was a little below 2023 and the 6 year September average.