May 2020 Weather Report

Overall a rather damp and cool month.

Rainfall

Possibly the big item for the month thanks to the major event from 21 to 25 May giving 98.4 mm for my weather station.  As this chart shows the total fall for the month (114.4 mm) was well above both the average and 2019.  I have posted elsewhere with some details of the event. 

As a result of these very welcome falls my pro-rata projection to the end of the year has taken a sharp upwards turn.  At the end of the month the projected annual amount is 890 mm compared to 780 at the start of the month.

The post linked above also commented on the problems with the BoM station due to the rain collector being block with fire debris.  That has now been resolved: the total amount recorded seems to be consistent with other records in the area and is still currently shown on the BoM site (although the hourly records were rather different to other stations.

It is also noteworthy that the falls did not go far inland.  Folk have mentioned falls at Gipsy Point of around 70 mm and Wallagaraugh around 60 mm.

Temperature

As will be apparent in what follows the month was cool overall with no outrageous temperatures in either direction.  That being said:

• the BoM site recorded 24.2^oC on the 9^th  which was the 14th warmest May temperature (out of 789 records).   As would be expected my WS was slightly warmer recording25.7^oC on the same day.
• And the BoM also recorded a minimum of 4.1^oC on the 15th which was the 16^th coldest May night! (My site managed 4.8^oC on that night.)

My overall assessment off the temperature is guided by the difference between the average temperatures observed in a period and the long term average.  This started off low for May but gradually approached 0, ending at -0.29^oC.   

There were less than expected days with both extremes above average and more days than expected with both below average,

Maximum temperatures.

The average maximum temperature was slightly below both the average and the value for 2019.

Over time the series of average maxima for May looks very variable.  While a trend line seems to slope down, the value of R² is way too low for significance.

Minimum temperatures 

Somewhat higher than average and almost identical to 2019.

The time series of minima seems to slope up, but again the value of R² shows it is in the category of "Move along folks, nothing to see here!"

Humidity

I continue to be surprised at how similar the morning and afternoon humidity readings are!  

I was surprised to find that the latest version of EXCEL includes a chart category of "Combo" which allows combination of different types of chart.  So here is a line chart of 0900 hrs humidity with a bar chart of rainfall!  I am a little surprised that there isn't a more obvious linkage.

Overall the morning average humidity was well up on both the long term average and the value for 2019.

In contrast the average afternoon reading was below the average, and only slightly above the 2019 value.

Wind

The average daily wind run was slightly below 2019 and a little more below the average.  The two longest daily runs were ~210 km which wold place them about 50^th out of 475 records.

As always seems to be the case with statistics about wind there are many ways of presenting material about it.  In the pie chart below I have shown the result of using number of observations as a counting unit.

This shows the dominance of wind from SW round to N.  This may in part reflect my site being sheltered from Easterlies.  I also looked at using hourly wind run as the metric but the two series have a correlation coefficient of 0.92 so show very similar patterns.  The most noticeable difference is a bigger slice of pie, for the North category, suggesting that winds from that direction are stronger,