December 2018 Weather Report

This will be my last monthly weather report from Carwoola as we are leaving on 19 January!

Rainfall

We had some!  Needless to say it fell pretty much in 2 days and flooded the Creek worse than I have ever seen it.  At this point the water would have been we over 1 metre deep going across the ford.

Here are the graphs: well above last year and the month average.
 As shown in this second graph it was the first month of the year in which we got and above average fall.  This did get us above the lowest fall ever recorded in Carwoola (which I will cover in more detail in the Annual report which I will compile soon).
I have continued on my exploration of long cumulative series for rain.  It is now up to 24 months and the trend continues to show a dive..
 However focusing on the end of the original series shows a hook which is exaggerated if the series is restricted to 2018.  Has the series of months with poor rainfall ended?  Who knows - there have been other short upturns that have not been sustained.

Temperatures

I will begin with maxima and minima through the month.
 It will come as little surprise to find that the month started off cool-normal and then developed a sting in the last week, with a maximum above 30oC for 8 days in a row (our  longest run of days over 30oC is 12 - and I suspect that will be broken by the time this episode ends.

Maximum Temperatures

The average maximum temperature for the month was a little higher than average and a fair bit higher than last year.
 I define a heat wave as 3 or more consecutive days over 30oC.  I then count the number of days in such a stream to get heatwave-days per month.  So far this heat year (May 2018 - April 2019) is a little below average, but December was a little higher (11 days rather than 10.4).

 Minimum Temperatures

As is the frequent refrain recently, the minimum temperature was well above average.  It was slightly down on last year

Average temperatures

In view of the above it isn't surprising that the average temperature for December was well above average.
The difference between last month and 'normal' is illustrated by the anomaly, which is strongly positive for series since 2013 (records from my weather station) or 2010, using some approximations based on older records.
Looking in detail at December I calculated the difference between mean temperature month-to-date and the equivalent average using my data.  The shows clearly the cool period mid month and the heat wave later.

Humidity

My overall conclusion was that the month was normal for humidity.

Looking at the daily readings for relative humidity (rH) shows the considerable variability from day to day, usually with the 9am reading above that for 3pm.
I was struck by the low 9 am reading for 2 December but looking at the hourly readings for that date it shows a consistent pattern.  It also follows a very low reading for 3 pm on the 1st.

Overall the average 9am reading was lower than average and below 2017. 
 For the afternoon reading the value was well below 2017 but a little above average. 

Wind

The month was about average for windiness.

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