Rainfall Shortage Jan 2000 – Mar 2019

Severe and extreme rainfall shortages Jan 2000 to Mar 2019

The current drought now has an extreme rainfall shortage of 84 months duration that must have commenced in 2012.

A new graph

This graph shows the onset, persistence, and breaking of episodes of extreme and severe rainfall shortage (droughts) at Manilla since 2000. It is a part of a graph of the complete historical record from 1884. In this case, the time axis is expanded to resolve individual months.

Complete record severe and extreme rainfall shortagesThe features of this “onset-to-breaking” kind of graph and the data analysis are explained in the post “Rainfall Shortage History: Manilla”.

Extreme shortages, up to the 1st percentile, are shown in red and severe shortages, up to the 5th percentile, are shown in grey.
The dashed line labelled “Last Good Data” is a limitation to determining cumulative rainfall deficiency. Future observations may make any point to the right of this line more extreme.

The pattern of rainfall shortages from 2000

Shortages before 2018

In 2000 there were no rainfall shortages classed as “severe”. There had been hardly any since 1994.
The drought that occurred in winter 2002 had extreme rainfall shortages at all durations from 3 months to 12 months. Severe shortages extended even further: from 2 months to 30 months. However this was a much shorter drought than six others in the history of Manilla.

Although severe rainfall shortages (grey) occurred at intervals between 2002 and 2018, they formed small clusters, mainly at short durations. Years affected were 2005, 2008, 2009, 2012, 2013, 2014, and 2017. By 2014, there was public concern about shortage of rainfall. Although there were few seasonal severe shortages at that time, the graph shows that there were severe shortages at durations from 12 months to 30 months through 2013 and 2014.

With the benefit of current data, we can see that severe and even extreme shortages of duration longer than 60 months were, in fact, initiated in 2012 or earlier. They were not apparent at the time, however. In October 2016, in a post “Is There Any Drought Now?”, I argued that there was no evidence of drought at that time.

An alternative expression of rainfall status during this time is a graph of smoothed rainfall anomalies in the post “17 Years of “Droughts and Flooding Rains” at Manilla”.

Shortages at 2018

Shortages of rainfall became alarming in 2018. The winter months had extreme shortages of 2-month to 6-month duration. Earlier and later dry months contributed to a 15-month extreme shortage, such as had not occurred since 1966, half a century earlier.
After November 2018 none of the short-term rainfall totals for durations less than nine months has been even a severe shortage. In other respects, the drought has deepened. As recent monthly rainfall values have scarcely risen above normal, durations of severe or extreme shortage have become longer and longer. As at March 2019, extreme shortages prevail at 30 months, 72 months and 84 months. Severe shortages prevail at even longer durations, now up to 120 months (10 years).

Other Current Graphs

Other graphs of the drought, current to March 2019 data, are in two posts: “March Rain Leaves Drought Extreme”, and “Rainfall Shortage Sequence 03/2019”.


The Millennium Drought absent
“Rainfall Shortages” or “Droughts”?
Short droughts are worst

The Millennium Drought absent

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Rainfall Shortage History: Manilla

Complete record of droughts, Manilla NSW

Manilla had great droughts in 1902, 1912, 1940, 1946, 1965, and 2018.

A new graph

This new graph records all historic periods of severe and extreme rainfall shortage at Manilla NSW. Data show 25 values of duration from 2 months to 360 months. Unlike the graphs of rainfall shortage in earlier posts, this graph shows the months of onset, persistence, and breaking of each occurrence. [See the Note below: “An innovative graph”.]
Extreme shortages (up to the 1st percentile) are shown in red and severe shortages (up to the 5th percentile) are shown in grey.
The dashed lines labelled “First Good Data” and “Last Good Data” are limitations that apply to all cumulative rainfall deficiency data. [See the note below: “First Good Data; Last Good Data”.]

A more detailed graph for the years 2000 to 2019 is shown in another post.

More recent graphs are in “Rain Shortage Jan 2000 – May 2019” and “21stC Rain Shortage Oct ’19”

“Rainfall Shortages” or “Droughts”?

Although droughts involve other factors, rainfall shortage is decisive. Some other factors, such as daily maximum temperature anomaly, vary in the same sense, Australia-wide.
Recognised times of drought at Manilla appear on this graph as extended periods of severe or extreme rainfall shortage .
To simplify, I have separated the graph into three parts according to the duration of the shortages: seasonal droughts, great droughts, and decadal droughts.

Complete record of seasonal droughts

Seasonal droughts.

Droughts with extreme shortages of rainfall that lasted up to nine months happened often. Counting those with more than one red marker, there were 16 seasonal droughts in 136 years: about one in each nine years. Gaps as short as four years happened around 1920, while the longest gap of 16 years came between 2002 and 2018.
The most common season of extreme rainfall shortage was winter, with 8 cases. Autumn had 5 cases and spring 3 cases, while summer had none.
Some of these seasonal droughts became Great Droughts.

Complete record of the great droughts

The Six Great Droughts: 1-year to 9-year duration.

According to this graph, Manilla has suffered six great droughts, attested by extreme shortages of rainfall at more than 2 of the 13 chosen duration values from 12 months to 108 months. They were:

(1.) 1902 (the Federation Drought);
(2.) 1912;
(3.) 1940 (first part of the World War II Drought);
(4.) 1946 (second part of the World War II Drought);
(5.) 1965;
(6.) 2018.

[The absence of the Millennium Drought is discussed in the Note below.]

BoM continental rainfall maps

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Rainfall Shortage Sequence 03/2019

Sequence of raiinfall shortages to March 2019

By March 2019, extreme shortages of rainfall occur at durations from 12 months to 30 months.

This contour plot shows the progress of the drought at Manilla up to March 2019. Colours show rainfall shortages as percentiles. Dates plot along the top, and durations down the side.

One month rainfall totals (on the top row)

By March 2019, there had been eight months without serious monthly rainfall shortages. The months of serious rainfall shortage (light brown) were earlier, in May, June and July 2018. The only other month in the last two years with such low rainfall was September 2017.

Shortages lasting less than one year (rows 2 to 9)

As the effects of low monthly rainfall added up, extreme shortages appeared (dark brown). That is, rainfall totals in the lowest 1% of the historical record.
By June 2018, the 2-month and 3-month totals were already extreme shortages. Similarly, by July, the 3-month, 4-month, and 5-month totals were all extreme shortages. By September 2018, extreme shortages extended as far as 9-month totals. That total, adding up the nine months from January to September 2018, included only one month (February) that had rainfall above normal.
In these shorter durations, extreme shortages were rare after September 2018. The final month plotted (March) includes no shortages (not even “serious” ones) for durations from 2 months up to 6 months.

Shortages of 1-year to 3-year duration (rows 12 to 36)

By August 2018, an extreme 15-month shortage appeared. The 15-month total then included not only the dry months of winter 2018, but also the dry month of September 2017. By September 2018, the 15-month total became the driest on record (400 mm). By October four totals in this group (12-, 15-, 18-, and 24-month totals) were extreme shortages. That was true again in January 2019. By that time, some dry months in 2017 were excluded, but dry months in the 2018-19 summer were included.
In February 2019, as the four extreme shortages of the previous month persisted, the 12-month total became the driest on record (271 mm). March also had four extreme shortages in this group, but now they were at 12, 15, 24 and 30 months. The 24-month total (769 mm) was the second-driest on record and the 30-month total (1078 mm) equal driest.

A related graph

A line graph of the rainfall status for March 2019  extends to durations much longer than the 36 months shown in this contour graph. It reveals that extreme shortages exist at durations of six years and seven years.

Data and method

This kind of graph simply displays the time sequence, month by month, of rainfall shortages that I have displayed on line graphs prepared for each month. In the post for the most recent line graph (March 2019) I have described my method of analysis and its limitations.