November 2018 Weather Report

My summary of the month was that it ended up being close to average in both rainfall (only 1.8mm below average) and average temperature (unusually for the recent past, below the average since 2010, by 0.6^oC).  Humidity in the morning was about average, but a tad elevated in the afternoon.  The outstanding departure from 'nomal' was that it was very windy.

Rainfall

As noted in the preamble very close to average.  That varies a bit according to when one takes the average:

• since 2010 the average is 84mm (as the Novembers in 2010 and 2011 were very wet);
• taking the whole range back to 1984 it drops to 76mm (which is probably the best measure); 
• but using all my data since 2007 (which is what I have traditionally used for these graphs) is 85mm.

2017 was similar to this year so still a bit below average on this graph..

It still seems that we are are in a long term drought which has now run for 23 months (since January 2017).  Looking at 23 month totals the last high point on the chart was March 2011 and looking at rolling 23 month aggregates since then shows how the situation has got worse.

The fair fall in November has perhaps shown a slight leveling of the original data but far too little to say we're anywhere close to out of trouble yet.

Temperatures

Maximum temperatures

The long term chart (since 2010) shows this November to have been slightly cooler than both average and 2017.

 Looking at the daily maxima, the start of the month was a little alarming but a series of cold fronts saved us from serious heat as the month progressed.

Over Summer one of my analyses is to compare the number of heat wave days.  My definition of a heat wave is a period with 3 or more consecutive days with a maximum >30^oC.  This can wrap over the end of a month and so it did this month, with the maximum on 31 October being over 30^oC as were the first 2 days of November.  Thus that was a heat wave, and October scored 1 heat wave day and November 2.  (There was one additional day >30^oC but not a heat wave.)  

In 2017 there were no heat wave days in October or November so the comparative chart looks a little strange.

Minimum Temperatures

As is often the case the average minimum temperature was slightly higher than the average since 2010.  It was slightly lower than 2017.

 There daily values show a very warm patch early in the month with mainly lower values thereafter.

This led me to check the November minima for all years since 2010.  The value of 18.5^oC on the 2nd was the highest November minimum recorded for Carwoola, and the 15,4^oC on the 14th the 6th highest.  However looking at highest minima by day only 3 days in 2018 are the highest.  In contrast 2010 and 2012 both have 6 days with highest minima.  This is possibly a good example of the need to look closely at claims of extremes to ensure the data isn't being cherry-picked.

Average temperatures

Rather than simply look at the daily averages I compiled a series of month to date averages for 2018 and the 6 years since 2013 for which I have have measured average temperatures.  As would be expected from the two previous sections the month begins well above average and ends up below average.

Another way of looking at this is by the anomaly which is the difference between the current monthly average temperature and the long term average for the month.

Using both my 6 year series and an extended series, with estimated averages for 2101-12, shows the month to be a bit cooler than average. The series over the year is too variable to display a significant trend.

Humidity

My traditional metric for humidity has been the value at 1500hrs (3pm for real traditionalists).  I chose this as the early morning (ie 0700 or earlier) values always seemed to be a lot higher and stable.  However by 0900 - the second standard time presented by BoM - some variation is evident so more recently I have presented both series , based on series starting in 2013.  Here are the two longer term series.

The value for 0900 is very close to both the 6 year average and last year.

 The 1500 series shows this year to be below 2017 but somewhat above average.

Looking at the daily values through the month shows the greater stability of the morning readings and that they are usually higher than the afternoon readings unless it is a rainy day.  The chart clearly shows the passage of rain events!

Wind

Subject to the usual caveats about the siting of my weather station this month was rather windy!  This is to be expected with several fronts coming through.