Saturday, 2 September 2017

Carwoola weather August 2017

The calendar lined up this month so the final report was in the Gazette!
In brief, a fairly dry and mild month, with an outbreak of chilliness in the final part of the month.

Rainfall

At least there was some (39mm) in August.  
Although below my (arbitrary) reasonable level of 50mm; the fall in 2016 and the 10 year average, it was still a bit better than some months this year.  The extrapolated annual total is now close to 400mm - only 10mm below the record lowest recorded in 2006.  Comparing 2017 with average year-to-date falls shows that we are above 50% and the ratio is slowly increasing.

Temperatures

A rather mild start to the month, followed by a cool finish.
 The average maximum was a little cooler than both last year and the long term average.
 The average daily minimum was approximately a degree above the long term average.  Note that for 2016 the average minimum was barely above 0oC so doesn't register in the chart.
A further demonstration of the level of coldness is the number of frost-days.  The next chart compares the long term average number of ground frosts (minimum below 2oC) and air frosts (minimum below 0oC ) with the numbers for 2017.
 In essence we had below average ground frost but when it dipped below 2oC it kept going down and gave an air frost (also called a hard frost by some).

An issue to bear in mind is that my reading of minimum are based on a calendar day whereas the values reported by BoM are based on a day ending at 9am.  Thus if there is a warm night, but the following evening is cooler, the minimum for the 24 hour period will take the latter value.  That was notable this month, especially on the 11th, when the overnight minimum of 9.1oC was the second highest recorded in the area but the 24 hour average of 5.7oC was not remarkable.

Humidity

The daily readings for 1500hrs (3pm for those who like the old money) are fairly unremarkable.  
 Comparison with longer term data shows it to have been drier than both the average and 2016.

Wind

My impression of the early part of the month was of very strong winds.  This made it much of a chore to get out for a waddle!  Fortunately my weather station supports this judgement.
Although I don't place great reliance on my wind data due to siting of the station I thought it interesting to check my statement that it was windier in the early part of the month.  This chart shows 2 measures of windiness - they correlate quite well - which confirms it was much windier up to the 20th than after that date.

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