Weather Report November 2020

 In summary a warm and damp month.

Rainfall

At Angophora Drive my Weather Station recorded 75.4 mm of rain through the month.  This compares with 57.8 mm at the BoM Mallacoota site, 31.2 mm at BoM Gabo Island and 60.9mm at a private station in the town centre.  The main causes of the difference are storm cells around the 13th and 23rd (different station reset times confuse matters somewhat) giving localised high readings.  This is reflected in the rain rates with a maximum rate on the 12th of 164mm/hr and on the 23rd of 60.4mm/hr. For a change, my WS received the cells and the other sites missed out.

Looking at the month as a total the fall was well above November 2019 and ~20% above the median fall for the area.

The cumulative rainfall for the year so far is 931 mm and doing a pro rata estimate of the total for 2020 gives 1008 mm for the year as a total. 

Temperatures

My overall assessment of temperatures is the difference between the average temperature for the month and the the long term mean average.   I calculate the average as (Max+min)/2 doing the calculation on a daily basis using data for  the BoM site at Mallacoota airport.  Over the month as a whole the anomaly came out to +2C, which is quite a high value.  The next chart shows the development of the value through the month.

Looking at the daily readings the average as calculated was above the long term mean equivalent on 21 of the 30 days. There were only 5 days in which both maximum and minimum were below the long term means but 17 days where both were above the long term mean.

The other overall presentation is the daily extremes.

Minimum Temperatures

The lowest minimum recorded in the month was 7.2C on the 8th.  More than 10% of minima for Novembers are lower than this.  The average minimum for the month was very much higher than 2019 or the long term average.  This is not surprising as the minimum was above the long term average on 23 of 30 nights.

Maximum Temperatures

The highest maximum for the month recorded on my Weather Station was 30.8C recorded on the 22nd.  There was one other day above 30C.  Comparing my results with the past shows 2020 as having a considerably higher average maximum.  

Considering a smoothing polynomial for both series suggests that the 2020 series of average daily maxima was a little above the (largely BoM data) past average for the first 6 months of the year.  That is quite usual as the coastal exposure of the BoM site takes the edge off hot days.  However the gap widens considerably from August onwards.

A similar statement can be made if the comparison is restricted to BoM data.  I conclude that La Nina has kicked in.

Humidity

The daily traces for humidity at the two standard times are as usual quite variable.  The rainy days stand out where the afternoon reading is very close to, or above, the morning reading.  

On the other hand it is unusual to record an rH of 40% as happened on the 4th only: 1.2% of my humidity readings (since February 2019) are that low.  I have prepared confidence intervals (average + 1.96 Standard Deviations) for each hour across all months.  As shown below a reading of 40% is very close to the lower limit for 1500 hrs.

The value of rH  for 0900 was above average ...

... while that for 1500 was below average, but above the value for 2019.

Wind

The chart of daily wind runs shows several days above 200km, with an impressive 357 km on the 11th.  That is the 5th windiest day since we moved here in February 2019.  

There has been a bit of discussion on Facebook about the wind on 29 November causing boats out at sea to run for home, and blowing many pelagic birds inshore.  That day doesn't show up as extraordinary in the daily chart.  That is because it was a short blast of wind as a change came through, compared to the more or less continual long hourly runs of the 11th.

In the historical graph below I have adjusted the long term average runs to allow for the greater exposure of the BoM site.  The month was less windy than 2019 (both measured at my weather station) but a little above the expected value from the long term average

In terms of wind direction I have graphed the direction of the wind at the hour and the direction of the strongest gust in each hour.  I am still contemplating what this all means.