The BoM has the Climate Outlook at "Neutral" between El Nino and La Nina with a tendency towards La Nina. That would imply an expectation of above average rain. Not in this District in August: very dry (in terms of rain at least) but also ending up extremely warm overall, compared to average temperatures for the month. As is often the case, it appears that the answer is blowing in the wind (if Mr Zimmerman doesn't mind me borrowing a phrase).
Rain
What is this thing called 'rain'? We totalled 22.6mm for the month, the 6th lowest since my records begin in 1977. Obviously well below average (35.7% of median) but better last year's miserable fall of 13.8mm. The benefit of a low fall is that the low daily falls actually appear in a chart!
We are however still well in front of 2023 in total (by 285mm) and the pro-rata estimate for the year as a whole is still 1066 mm.
Temperatures
The final value for the temperature anomaly was +1.8C. That is not the highest value of the anomaly I have calculated (there are 3 higher values) but only +2.0C in November 2020 is significantly higher. Despite this high recent value, the 12 month moving average still suggests a downward movement may be evident, although the trend of the average is still upwards.
The development of the anomaly through the month shows a rather cold start to the month followed by a steady increase.
The extreme temperatures show that the cause of the high anomaly is the very high maxima recorded in the month.
A further point of interest in temperatures was the daily ranges. For most recent months a combination of high minima and low maxima has meant the daily temperature range has been below the range of the averages for a high proportion of days in the month. For August the range in the average was higher on only 6 days, reflecting the consistently high maxima and low (or at least relatively low) minima.
Minimum Temperatures
The average minimum for the month was 8.39C. The highest minimum temperature was That was the highest recorded since my broad series (Airport and home) begins in 1993. The next chart shows the 6 year series of readings on my weather station.
It will be no surprise that this year is top of the pile. The highest minimum temperature was 13.3C on the 13th: this was =6th highest August minimum. 11 days were more than 1 SD above the monthly average (ie significantly hot).
While there were 3 consecutive days of minima more than 1 SD
below the monthly average, these were not accompanied by significantly low maxima and thus do not amount to a Cold Spell.
Maximum temperatures
The average maximum for the month was 19.12C, the highest average maximum for August by 0.5C.
The highest maximum was 'only' 23.7C which is the 21st highest August maximum in my records (including a small adjustment to make the WS and Airport data more consistent). There are two other WS record of higher maxima. What has caused the high average is the number of days significantly above the monthly average maximum:
- only 6 days were below the average maximum for that date;
- of the 25 days above average
- 15 were more than 1 SD above the monthly average and
- 4 of them were more than 2 SD above the monthly average.
Further, there were 10 days in which both maxima and minima were significantly above average. It seems a little panic-ridden to describe a period with a maximum temperature ~22C as a "Heat Wave" but it is certainly significant that of the last 19 days of the month only three of the extreme temperatures were below average for the date and of the last 8 days of the month only 2 readings were less than 1 SD above the monthly average.
Humidity
The average morning rH at 82.1% was well above average while the afternoon reading was close to average.
The values for 31 August - especially the afternoon reading - were so low that I assessed the pattern through the day. It looks normal so I will regard this as an effect of a constant wind from the NE.
Wind
I have difficulty with wind, as my WS is far from optimally exposed (too low and too sheltered from the Southern half of the compass). There is relatively limited information available (at no charge) from BoM. The average daily wind run this month was about normal for August.
Of more interest this month is material about the the direction of the wind.
This shows that 61% of the records of wind (excluding those with no wind run - ie calm) in August came from the segment of the compass from NW to NE (31% of the compass). Looking at all WS records 42% of windy records came from that segment. I have taken this above as an explanation of the Humidity data, and expect that it also contributes to the high temperatures observed.
Tempest data
A friend operates a weather station neat the Wharf using the Tempest app. This includes some very interesting data on Lightning Strikes (within 40km) and Solar Radiation.
The solar Radiation chart is particularly interesting in understanding the need for running the hot water booster and why my solar feed in varies (beyond the appalling feed in tariff now offered).
As is Pultenaea daphnoides.
Daviesia latifolia was an addition to the Sptember list for the District. A classic 'egg and bacon' flower.
Glycine clandestina was evident rather than being clandestine! (NB the big leaves are Hardenbergia, the sets of 3 are Glycine.
Viola hederacea
Another addition to the September list: Prostanthera rotundiflora.
