New drought records in August 2019

Rainfall status July-August 2019

Graph of Rainfall Shortages

This graph shows all the present rainfall shortages at Manilla, short term and long term, as percentile values. The latest values, as at the end of August, 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.]

Record low rainfall values

August rainfall of only 5.6 mm at Manilla has brought more drought records. The rainfall totals for 18-, 24-, 36-, 72-, and 84-months are new record lows.
The record-low 36-month total is remarkable. Only the great droughts of 1947, 1914, and 1967 had rainfall nearly so low for so long, but the current 36-month total (1283 mm) is more than 50 mm lower than in those great droughts. Given that Manilla’s mean  annual rainfall is 652 mm, 1283 mm represents less than two years of rainfall in three years.

Severe and extreme rainfall shortages

For plotted durations longer than four months, only the very longest (30 years) is not a severe or extreme rainfall shortage. For durations beyond 84 months (including 30 years) every total is lower than has been seen since 1954, 65 years ago.


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

Drought worse in July.

At Manilla, most rainfall totals just got lower.
Rainfall status June and July 2019

Graph of Rainfall Shortages

This graph shows all the present rainfall shortages at Manilla, short term and long term, as percentile values. The latest values, as at the end of July, 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.]

Results for July

Rainfall totals for months to July 2019 are the lowest ever registered here for six of the twenty-five chosen rainfall durations: 15-, 18-, 24-, 30-, 72- and 84-months.
Only three of the chosen durations do not have serious rainfall shortages below the 10th percentile: 1-month, 3-months and 360-months. Even those three values are far below normal, at the 12th, 14th, and 14th percentiles.

Weatherzone forum closed

I posted a provisional version of this graph to catch the final deadline for posting to the weatherzone forum. My first post was nearly 16 years ago.
That forum is now closed to postings and will close completely in November. It closed due to lack of public interest in climate and weather in Australia.


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

June breaks more drought records

Rainfall status May-June 2019

Graph of Rainfall Shortages

This graph shows all the present rainfall shortages at Manilla, short term and long term, as percentile values. The latest values, as at the end of June, 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.]

Changes from May to June

The June rainfall of only 4.8 mm took Manilla’s rainfall status curve back to where it was in April.
Five records for low rainfall totals have been broken yet again: the totals for 15-, 18-, 24-, 30-and 72-months. The 84-month total at June (3660 mm) is also extremely low, but ranks second-driest to April 2019.
The record for a 15-month dry spell, which had stood at 404 mm since 1912, has been broken four times in this drought, and now stands at 367 mm. That is down by 37 mm, or nearly 10% below the 1912 figure. The 24-month record had stood at 766 mm since 1966 when it was broken this April, May, and June. It now stands 73 mm lower, at 693 mm.


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

May 2019 rain gives some relief

Rainfall status Apr-May 2019

Graph of Rainfall Shortages

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

Changes from April to May

Above-average rainfall in May relieved the drought situation in some ways. Rainfall shortages of 3-, 4-, 5-, and 6-month duration are no longer serious. The 9-month shortage is reduced from severe to serious, and the 12-month shortage from extreme to severe.

May rain did not prevent the rainfall total for 15 months falling to the record low value of 388 mm. The record, which had been set at 404 mm in 1912, has been broken three times in this drought: to 400 mm in September, 397 mm in April, and 388 mm in May.

Nearly all rainfall shortages at long and very long durations have been reduced to some extent. However, extreme shortages persist not only at 15-months, but also at 18-, 24-, 30-, 72- and 84-months.


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

April 2019: 7 lowest rainfall totals

In April 2019, rainfall totals were the lowest-ever values for 1 month and for 15, 18, 24, 30, 72, and 84 months.

Rainfall status Mar-Apr 2019

Graph of Rainfall Shortages

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

Record and near-record low rainfall totals

There never has been a month at Manilla when rainfall totals have included so many record or near-record low values.

  • The 1-month total for April is zero (as in April 1912, 1925, 1942, and 1971).
  • The 12-month total of 283 mm is second-lowest after February 2019 (271 mm).
  • The 15-month total of 397 mm is a new record, beating September 2018 (400 mm).
  • The 18-month total of 510 mm is a new record, beating April 1966 (514 mm).
  • The 24-month total of 745 mm is a new record, beating July 1966 (766 mm).
  • The 30-month total of 1005 mm is a new record, beating March 2019 (1078 mm).
  • The 72-month total of 3060 mm is equal-lowest with February 1903.
  • The 84-month total of 3653 mm is a new record, beating February 2019 (3672 mm).

Other changes from March to April

When rainfall in April was 55 mm less than in March, the short-duration totals for 3, 4, 5, and 6 months became serious shortages again.
New severe rainfall shortages appeared at the very long durations of 144 months (12 years) and 240 months (20 years). Such shortages have not been seen in half a century: not since 1969 in the case of 144 months duration, and not since 1950 in the case of 240 months duration.

May and June 2019 data

Data for the following month, May 2019, is plotted in the same way in the post “May 2019 rain gives some relief“. See also “June breaks more drought records”.


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

March rain leaves drought extreme

Above-average rainfall in March reduced the shortage of rainfall in the last 3 months. It did not relieve extreme shortages at durations between 12 months and 7 years.

Rainfall status Feb-Mar 2019

Graph of Rainfall Shortages

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

Good rain in March

A rain front at the end of March 2019 that brought about 40 mm took the March total up to the average. This raised the 2-month and 3-month totals nearer to normal. It did nothing to increase longer-duration totals.

Extreme rainfall shortages

By February, six of the eleven rainfall shortages measured over durations from 12 months to 7 years were extreme. (That is, those totals were in the driest one percent in history.)
Despite the high rainfall of March, March figures also record six extreme shortages. The 18-month total is no longer extreme, but the 30-month total has now become extreme.
Two of the rainfall totals (plotted on the 0.1% line) are near-record low values. The 24-month total of 769 mm is the second lowest after July 1966 (766 mm). The 30-month total of 1078 mm is equal lowest with October 1966.
Data for February, plotted on the thinner line, show the record low values for 12 months (271 mm) and for 84 months (3672 mm).

The previous 24 months

The development of this drought through the previous 24 months is shown in the later post “Rainfall Shortage Sequence 03/2019”. A contour graph shows severity of shortage by contoured layer tints, with serial months on the x-axis and duration of shortage on the y-axis.


Further Explanation

[Update 5 April 2019.]

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

This graph is based on analysis of monthly rainfall totals from 1884. Using the spreadsheet application Excel, I calculate cumulative totals and their percentile values. Using these values, I identify rainfall shortages as serious, severe, or extreme .

Cumulative rainfall totals

I prepare two tables. The rows in each table are serial months, more than 1600 in total. The columns in each table are headed by the selected number of months, n, as specified below. In the first table I cumulate the rainfall totals. First, I add each month’s rainfall total to that of the previous month for a 2-month total. Using the previous two months, I get a 3-month total, and so on. In this way, I get n-month rainfall totals from n = 1 up to n = 360 (30 years). However, I calculate for only the following 25 values of n:

n = 1, 2, 3, 4, 5, 6, 9, 12, 15, 18, 24, 30, 36, 42, 48, 60, 72, 84, 96, 108, 120, 144, 180, 240, 360

Continue reading

February: Two Record Droughts

Two rainfall totals to February 2019 were the lowest ever recorded at Manilla: 271 mm in 12 months, and 3672 mm in 7 years.

Rainfall status Jan-Feb 2019

Graph of Rainfall Shortages

This graph shows all the present rainfall shortages at Manilla, short term and long term, as percentile values. The latest values, as at the end of February, are shown by a thick black line with large circles. Those from one month earlier are shown by a thinner line with smaller circles.

The pattern

The very low rainfall of February 2019 (10.6 mm) has driven the rainfall totals lower than they were in January for nearly all the durations that are shown.
The rainfall totals up to 6 months are still not “serious” shortages (below the 10th percentile), but the only other total that is not now a serious shortage, or worse, is that for 30 years (360 months).
In recent months, extreme shortages (below the 1st percentile) have persisted at durations of 12 to 24 months, and at durations of 6 to 7 years.

Record-breaking drought

Two rainfall totals to the end of February are new drought records for Manilla.

The 12-month total of 271 mm beats 288 mm set in October 1965.
The 84-month (7-year) total of 3672 mm beats of 3699 mm set in March 1903.

Earlier, another record had been broken in September. The 15-month total of 400 mm at that date beat 404 mm set in May 1912.


Further Explanation

Drought 2018 contour chartMuch more detail was given in the post: “Contours of Manilla’s 2018 Drought” (with data up to October only). Notes include: “Long-term shortages”, “Classes of rainfall shortage”, and “Manilla rainfall records”.