August 2022 Weather Report

 In summary, somewhat warm overnight, cool during the day and wet.  I believe the reports that La Nina is starting up again and, by my definition, reckon it might already have arrived.  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.

In summary I think Spring has sprung.

Rainfall

The total fall for the month (71.4 mm) was well above the median (62.4 mm) but very much below 2021 (145.8).

The difference between the monthly falls for 2022 and the median could be interpreted as showing the end of one La Nina in April and the next event starting up in July.  (That being said, the BoM definition of a La Nina is based on the values of sundry indicators: the high rainfall is an outcome rather than a part of the definition.)

The daily falls and maximum rain rate line up pretty well (a high rate giving a high fall is to be expected) but some times there is a short sharp burst (4th, 25th) while on other days (7th, 23rd) the higher amount and low rate suggest English weather (constant drizzle).

That led me to think about Irish weather (rains for 15 minutes every quarter of an hour) so I have checked through the 1298 daily records finding 1891 hourly records (out of ~31,000 hourly records) with >0.2 mm of rain (thus excluding records with mainly condensation from fog).  It shows that Mallacoota has very few days with many hours of rain (15 days - 0.8% - with more than 15 hours of rain).

As usual I have calculated a pro-rata estimate of the expected annual fall.  It has become quite stable for the last few months, at around 1500 mm for the year.

Were this to occur it would be the highest, or second highest, fall recorded at Mallacoota. The current highest fall is 1442 mm in 1985.  If we get mean falls for the remaining 4 months of the year, adding to the 954 mm already recorded, the total would be 1260 mm - the 5th highest fall.  The BoM 3 month rainfall outlook gives our area about 65% probability of exceeding mean falls (or 35% chance of getting less than average).

Temperatures

The overall indicator of temperature is the anomaly which this month showed that the average temperature for the month was 0.86C above the long term mean temperature.  This graph shows how the anomaly built up through the month.

Both the above charts show a warm start and finish to the month with a cooler period in the middle.  A similar picture comes from my weather station.  (The mean of minimum and Maximum are very close for both sets of observations.)

Minimum Temperatures

Using data from my weather station combined with BoM data for years prior to 2019 this month was very much above the long term mean for August and somewhat above last year.

Using just my WS information it appears the minimum was above other years for the start of 2022, dropping below for May and June but is now back above the other years.  This seems consistent with a move back to La Nina.

Maximum Temperatures

In contrast to the minimum series this year had lower maximums than both 2021 and the long term average (with years before 2019 adjusted for the tendency for the BoM site to have a lower minimum than my WS).

Looking only at my WS the pattern of "around the mark" early in the year followed by a drop and now a return to 'normal' is pretty similar to the minimum series.

Humidity

Quite a humid month with both 0900 and 1500 hr relative humidities above the 4 year average from my WS.

The daily measures for those times shows an interesting pattern with the two series in close agreement for most days but occasionally with the 1500 reading well below the 0090 reading.

The BoM series gives a very similar (or even lower) reading on the 1st, 5th and 15th of the month but a higher reading on the 30th.  The BoM readings for 1500 hrs can be affected by wind off the sea, which was evident on the 30th, and a site in town had a 1500 rH reading halfway between the two other series so I don't believe there is a quality issue for my observations.

Wind

My Weather Station shows a continuation of short runs.  I am unsure whether that indicates a problem with my WS or just relative calm.  Here is a chart for what it is worth.