21stC Rain Shortage August 2020

Manilla extreme and severerainfall shortages from onset to breaking January 200 to August 2020.

New data for monthly rainfall totals at Manilla up to August 2020 show an altered pattern since October 2019 in this worst-ever drought.

[For explanation of this graph, see below: “About drought duration graphs”.]

Shortages January 2000 to August 2020

At Manilla, acute seasonal droughts ceased in 2019

Two periods of extreme rainfall shortage had extended through the mid-winters of 2018 and 2019. These were acute shortages of seasonal to annual duration. However, by the end of 2019 these very short-term rainfall shortages had ended: they were no longer extreme shortages in the 1st percentile. Although they were not even serious shortages, the fact that monthly rainfalls were below average prevented district water storage levels from rising.
As the 15-month, 18-month, and 24-month shortages persisted beyond January they ceased being extreme (1st percentile), but became merely severe (5th percentile). By that time, these two to three-year rainfall shortages had lasted longer as extreme (1st percentile) shortages than ever before (such as in 1965 or 1912).

Continuing extreme rainfall shortages

Extreme rainfall shortages linked to the 2018-19 drought at Manilla are now concentrated in the mid-range of duration – about 3-years to 10-years.
From 30-month duration up to 240-months duration, nearly all the selected durations are coloured red for extreme rainfall shortage, persisting up to the current month (August 2020). In this super-drought, extreme shortages of longer duration consistently had onset earlier than those of shorter duration: the longest, that of 240-month duration, started before 2000. (At Manilla, historic droughts differ in their pattern of date of onset versus date of drought-breaking.)
Not all very long-duration shortages are currently extreme.
At 108-month duration, the severity ceased to be extreme in March 2020. Neither the 120-month duration nor the 150-month duration reached beyond a severe shortage at any time. At the longest duration on the chart (360-months), not even a serious shortage has yet appeared.

Complete Manilla drought record to Oct 2019

Compete record to October 2019

For context, I have re-posted the graph for the whole historic record to October 2019.

About drought duration graphs

These graphs show the onset, persistence, and breaking of episodes of extreme and severe rainfall shortage (droughts) at Manilla. The Continue reading

August 2020: still gripped by extreme drought

Rainfall status Manilla drought to August 2020

Little rain fell in twelve months

In the past 12 months, only February (165 mm) and March (53 mm) had adequate rain at Manilla. Rain was so scarce that the 12-month total was just under 500 mm, far below the average of 652 mm. So the drought situation has not improved lately.

Seasonal to annual shortages were not serious

Through the year, most rainfall totals for 12-months or less have been below the average, but not serious shortages. The acute phase of the drought was over by February, if not much earlier.

Two-year to eight-year shortages were extreme

This worst-ever drought for Manilla has been marked by extreme (often record-breaking) rainfall shortages with durations from two years to eight years. They persist in the data for August 2020 shown in this graph.

Twenty-year and thirty-year shortages

The shortages with the longest duration included here had been near the 70th percentile in 2012, but are now very much worse. The twenty-year (240-month) shortage is now in the 1st percentile.

How to read the graph

This graph shows all the present rainfall shortages at Manilla, short term and long term, as percentile values. The latest values are shown by a thick black line with large circles. Those from one month earlier are shown by a thinner line with small diamonds. [The method is described in “Further Explanation” below.]

Further Explanation

The following notes explain aspects of this work under these listed headings:

Data analysis

Cumulative rainfall totals
Percentile values
Severity of rainfall shortages

Limitations of this analysis

Monthly rainfalls form a single population
Observations are not retrospective
The rain gauge failed

Data analysis

Continue reading

August 2020: warm nights and cool days

Weather log for August 2020

Weather log August 2020 Manilla

In August 2020, both the second and third weeks had warm nights that raised the weekly temperatures. The night of the 15th was especially warm, above normal by 8.5°. With the warm nights most days were cloudy, and five days had more than 0.2 mm of rain. The highest reading, 17.6 mm, was on the 8th.
There were 11 frosts (normally 15).

Comparing August months

Climate August 2020 Manilla NSW

The last three August months have all had very low moisture values, with August 2019 being also very warm. This month was much more humid: a higher dew point (2.0°), cloudy skies (42%) and an extremely narrow daily temperature range (12.3°) that was 4° narrower than normal.
Rainfall, however, was only at the 38th percentile (27.8 mm). That is still far below the August average (40 mm) and has added little to depleted water storages.


I will report separately on the on-going drought. Extreme rainfall shortages persist.

Data. A Bureau of Meteorology automatic rain gauge operates in the museum yard. From 17 March 2017, 9 am daily readings are published as Manilla Museum, Station 55312.  These reports use that rainfall data when it is available. Recording resumed on 20 July 2019. The gauge failed again during February (25/02/2020 ), but was repaired on 11/3/20.
My estimates of early morning dew point have drifted anomalously low. From August 2019, I use data from the Tamworth Airport published graphs.
All other data, including subsoil at 750 mm, are from 3 Monash Street, Manilla.

3-year trends to August 2020

August narrow temperature range

3-year climate anomaly trends to August 2020

August raw anomaly data (orange)


Daily maximum temperature anomaly (all x-axes), was just below normal.
Daily minimum temperature anomaly (lower left): was just above normal.
Subsoil temperature anomaly (lower right): was above normal.

Moistures (moist is at the bottom)

Rainfall anomaly (upper left) was normal.
Cloudiness anomaly (upper right) was more cloudy than normal.
Dew point anomaly (middle left) was normal.
Daily temperature range anomaly (middle right) was extremely narrow (humid).

 Fully smoothed data values (red) 

Fully-smoothed data for the summer (DJF) of 2019-20 shows that the daily maximum temperature anomaly continued to fall from the record value of October 2019. The daily minimum and subsoil values were static.
All the moisture indicators (rainfall, cloud, dew point, and daily temperature range) continued to move downward, showing decreasing drought.
The partially-smoothed anomaly values through the autumn and winter were near normal. They were not nearly moist enough nor cool enough to relieve the on-going drought that had peaked with high temperature and low moisture anomalies in 1918-19.


January data points are marked by squares.

Smoothing Continue reading

My better sun mirrors

By 11.30 sun mirrors fill the patio with reflected light.

By 11.30 reflected sunlight floods into the patio.

In my blog post “Mirrors to reflect the sun“, I described sun mirrors I put up to reflect winter sunlight to warm my house in NSW, Australia. They were just sheets of cooking foil taped to a north-facing courtyard wall, and I had to remove them each summer.
Now I have better and stronger mirrors: hinged panels that function winter and summer. In winter they reflect sunlight, and in summer they give shade.
These simple hinged mirror panels should improve the indoor climate due to my “Heat Control Courtyard“. Compared to heliostats (see links in a Note below) they are cheaper and will not set the house on fire!

This post is also available as a PDF file My better sun mirrors.


The mirror panels

I bought the mirror panels from builders supplies as “FoilBoard insulation panels”, 2440 mm X 1220 mm X 20 mm.

These are “aluminium composite bonded panels (ACP)” of rigid cellular expanded polystyrene (EPS) (20 mm) bonded between two layers of aluminium (less than 0.5 mm). One aluminium surface has 97% reflectance; the other is pre-finished in shades of green using a fluoropolymer resin paint system. [Cost of five panels: $230.]


The fragile FoilBoard insulation panels had to be stiffened with frames of aluminium angle, corner brackets, and braces of aluminium strip. [Cost: $380.]


I had the panels mounted on ten “hinges” that allow them to be held in two positions:

(A) flush against the courtyard wall to reflect the sun to the house in winter, or

(B) raised above horizontal to provide shade in summer.

These are standard hardware items called “Whitco Window Stays”. [Cost for ten: $430.] Here, they operate as hinges, using friction to secure the mirror panels at any angle. [I must thank my builder, Keith Freeman, for selecting and using them in this way.]


Work on the new sun mirror panels began on 1 December 2019 and ended on 24 January 2020. Labour cost about $1800, while materials (given above) cost about $1050.

As soon as the work was done, I set the mirrors to provide summer shade until the end of February 2020. Then I re-set them to reflect winter sunshine until now (2 September 2020).

The finished mirror panels

Photo dates

Because the effect of the mirror panels depends on the seasonal path of the sun, I took separate sets of photos in June, to represent the eight winter months (March to October) when they acted as mirrors and in February, to represent the four summer months (November to February) when they acted as shades. Photos of hinge details were taken in February.

Hinge details

Whitco window stays that form hinges to support sun mirror panels in winter are set here to make the same panels give summer shade.

These window-stay hinges are set to support both panels to give summer shade.

Whitco window stays form hinges to support house-warming sun mirror panels to make them also summer shade panels.

These window-stay hinges are set to support panels for winter warmth on the left, and for summer shade on the right.

Continue reading