Weather Report May 20206

 The overall weather for the month was very warm and a tad above average for dampness.

Rainfall

After the very dry April it was good - apart from the lawn growth - to get a fall of 76.8mm (102.8% of the median fall for May).  It was also spread well across the month.

By the end of the month my pro-rata estimate for the year was 951mm, well below last year and similar to 2024.  

It seems that some long-range  forecasts are still talking about an El Nino taking effect in the coming months but the word from the BoM seems to be taking 20c in several directions (similar to "2 bob each way" but lacking that level of certainty).  

Temperatures

The temparature anomaly ended the month at +1.84^o C.  Through the month the series was always above 1^o C after a very high value at the start of the month.  (This is discussed more under the 'maximum' subheading below.)

Looking at the historical values of the anomaly this was among the higher values recorded and leads to a slight uptick in the moving average series.

In terms of extreme temperatures the daily series shows quite consistent values above the average for the date. 

I compared the values from my WS with those from the BoM station at the Airport.  Allowing for the known differences between the sites (IMO mainly due to wind exposure)the picture is very consistent.  

Minimum Temperatures

The average minimum for the month was 11.04^o C which is 1.6^o C above the long term mean and nearly 1^o C above the next highest monthly average.   Of the top 25 May minima 6 were recorded in May 2026, while 3 would have been expected: in view of the foregoing it is not surprising that the highest minimum for the month (17.8^o C on the 3rd) was the highest minmum recorded.  At the other end of the scale the lowest minmum (6.1^o C on the 22nd) was only the 16th lowest recorded.

Not surprisingly, in my time series this year is much above all other years of WS records.

Only 1 minimum was significantly below the monthly average but 9 were significantly above average and a further 3 values were very significantly above average.

Maximum temperatures

The average maximum for the month was 20.16^o C, 1.17^o C above the average maximum for May.  To my surprise it was not the warmest May which award goes to 2007 at 20.27^o C.  (In 2007 again there were many days above 20^o C but no outstanding result such as might cause me to doubt the value recorded.  The warmest day this year was 24.6^o C on the 26th.  Looking at the history of my weather station readings the daily maxima are not dramatic - the highest reading is only the 8th highest -but a high proportion of the hotter days were recorded this year.  (Of the 25 hottest May days, 8 were recorded this year.

The time series shows this year to be above the 7 other years for which I have WS data, but not as much as for the minmum series.

3 minima were significantly below the monthly mean value, 4 values significantly above the monthly mean value and an astonishing 16 values were very significantly above the  monthly mean value.  On examing the historic series it appears that the maxima for the month do not vary as much as other months (the relative standard deviation for May is 4.7%  whereas for March it is 6.4%).  My knowledge of meteorology is too limited to explain why this is so.

Humidity 

I have discussed the issue of standard times in the report for April, being the first month with my new WS.  I have taken the standard times as 6am (representing morning values) and 2pm (1400hrs, representing afternoon values).  In general terms this is sufficiently comparable with the BoM, administratively driven stds of 9am and 3pm.

For this month the most notable feature is the high values of the afternoon readings.

The morning reading for this month is well above - 2.1% points -  the average (since 2019).

For the afternoon reading this month was on average was 4.4 percentage points higher than average and from eyeballing the daily chart above would have been even higher withough the drop in the last 2 days of the month.

Wind

With the new WS I no longer have a measure of 'run' (although I muight investigate ways of estimating that when time permits) so have used two measures of gusts as my indicator of daily windiness.

The monthly gust chart below is a little worrying as both months with the new WS appear well above average, suggeting the change is due to the new WS.  We shall see, but do not sell the farm (nor the boat) on the basis of this chart.

Solar

Only available for the last two months so all I will offer is a measure of total daily watts.

The 2 prominent peaks in this chart coincide exactly with days in which the measures of cloud cover cited on the BoM site (compiled at Gabo Island) were very low.  I shall work out a way of charting this in the near future.

Lightning

I again use data from a friend's WS reporting to the Tempest Network which gives the number of strikes estimated within 40 km of the Mallacoota Wharf.  It is graphed below using a logarithmic scale to accomodate the very large number of strikes in February 2025.  265 (= log 2.42) strikes were recorded in May 2026, a relatively high number for May.