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.

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 →

Since the graph for May, the drought at Manilla has become more severe at all durations, from two months up to 240 months.

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

Shortages Jan 2000 to Oct 2019

Seasonal rain shortages recorded to October 2019 are extreme (1st percentile) in the winters of both 2018 and 2019.
For durations of 9 months up to 96 months, extreme shortages now occur at all of the durations shown . This is much worse than in May. At that time, shortages had not been “extreme” (red), but merely “severe” (grey) at the durations of 36-, 42-, 48-, 60-, and 96-months.
By May, “severe” shortages had already appeared at the very long durations of 120-, 150-, and 240-months. Now, there are also severe shortages at 108-months and 180-months.
The shortage at 240-months has now also become extreme (red). Very low rainfalls since May have dragged down the 240-month total to make it the sixth driest on record at Manilla. This links the short extreme drought of 2002  to become a part of the current drought. That would have seemed unlikely during later deluges, as in summer 2011-12.

Compete record updated to October

When the graph of the complete record of months of rainfall shortage at Manilla is updated to October 2019 it is clear that the current drought is one of the greatest droughts in history.
Now that an extreme rainfall shortage has appeared at 240-month (20-year) duration, along with a complete suite of extreme shortages from 2-months to 96-months, only the droughts of 1912 and 1946 are comparable. The Federation drought of 1902 may also have had a 20-year extreme shortage, but data for that duration are incomplete.

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 →