The climate at Manilla, NSW,was extremely hot and dry in nearly all the months of 2019.
In a normal year (See note below: “Manilla temperature Normals”), Manilla’s mean temperature has a cycle close to a sine-wave , being highest in January (25.9 deg) and lowest in July (9.5 deg). In 2019, the shape differed only in June being cooler than July.
Remarkably, every month of 2019 was warmer than normal. June, August and September were warmer by less than 1 deg, but December was 3 deg warmer, and January 5 deg warmer.
Normally, Manilla’s monthly rainfall pattern (see note below) has two modes, with a main peak in January and a second peak in June. In 2019 there was no such pattern. Rainfall in most months was about 40 mm below normal, and was even lower in January, February and December. Only March and May had rainfall somewhat above normal.
Manilla Temperature Normals
The town of Manilla, NSW, had no recognised record of temperatures. When I had collected data for more than a decade, I felt the need to set up “normals” to compare actual values with those that are usual.
[Earlier, I quoted various official definitions of climatic normals in this post.
A climate normal is commonly taken as an average over three decades. To serve my purpose, I judged that a decade of data would be sufficiently stable.]
I based my normals on temperatures observed through the decade beginning 1 March 1999. I found mean values for the (366) days of the year, then made a more regular curve by using first, second and third harmonics.
The graph shows mean maximum, mean average and mean minimum curves, as well as the resulting curve of daily temperature range. Numerical values that were posted earlier are repeated here:
Manilla’s dates of expected highest and lowest air temperatures during the year are marked on every “Weather” graph that is included in a monthly weather report in this blog. Each graph has curved dashed lines showing the “Normal” temperatures (Maximum, Mean, and Minimum) for each day of the year. The highest and lowest values in the annual cycle are marked on these curves. This list gives the dates of peaks and troughs and their seasonal lags in days after the solstice.
Highest daily maximum temperature (34.04°): January 20-21 (lag 31 days);
Highest daily mean temperature (26.19°): January 25 (lag 35 days);
Highest daily minimum temperature (18.44°): January 31 – February 1 (lag 42 days);
Lowest daily maximum temperature (16.91°): July 8 (lag 17 days);
Lowest daily mean temperature (9.35°): July 10 (lag 19 days);
Lowest daily minimum temperature (1.78°): July 13 (lag 22 days).
Apart from the peaks and troughs, one can see that the curves show a steeper rise in early spring. The rise is more marked and earlier for the maximum curve. This results in a wider daily temperature range at that time.
Manilla’s monthly rainfall pattern
As my normals for the rainfall of calendar months, I have adopted the mean values recorded in the 125 years 1884 to 2008 at Manilla Post Office, Station 055031. Values are shown in this table:
In the post of 20 June 2013, “A Seasonal Rainfall Model for Manilla, NSW”, I showed that the observed seasonal pattern fits very well to a model of two Gaussian curves of almost equal width but unequal height. The higher (summer) curve peaks at 84 mm/month near 27 December, while the lower (winter) curve peaks at 42 mm/month near 27 June. The peaks lag just 6 days after the solstices, and do not show the long and unequal seasonal lags that are seen in temperature data (above).
[There are discrepancies of less than 1 mm in monthly rainfall normal values between the table above and those cited in 2013. As the normal period, I replaced 1883 to 2007 with the more secure period 1884 to 2008.]