March 2020: no new drought records

Changing shortages

Despite high rainfall (165 mm) in February and normal rainfall (53 mm) in March, many severe and extreme shortages persisted. Only at durations shorter than one year were rainfall totals near normal. As in February, the 12-month total remained at 432 mm: a serious shortage.

Three near-record low rainfalls

Although no records were broken this month, three rainfall totals were the third-driest ever: those for 42-months (1508 mm), 84-months (3495 mm) and 96-months (4142 mm).

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

February 2020: one drought record left

Rainfall status Manilla Jan-Feb 2020

Changing shortages

Very high February rainfall of 165.4 mm further reduced nearly all rainfall shortages, especially short-term ones. The 12-month rainfall total (432 mm) now just qualifies as a “serious shortage” below the 10th percentile.
Despite the general improvement, 10 of the longer-term totals are still extreme shortages, below the 1st percentile. However, only one breaks a record.

One record low rainfall

Only one rainfall total was a new record low value: the 96-month (8-year) total of 4104 mm. This record, having stood at 4405 mm since November 1919, was broken successively in November and December 2019 and January and February 2020.

Record-breaking low rainfall totals from 2018

Until 2018, no new records for low rainfall had been set since 1971. Most records had stood since the droughts of the 1940’s, more than 70 years ago.
In September 2018, a new record was set for the 15-month total (400 mm).
Since then (to include February 2020), new records have been set for 12-, 15-, 18-, 24-, 30-, 36-, 42-, 48-, 60-, 72-, 84-, and 96-months. That is, at 12 of the 25 selected durations. Some records have been broken repeatedly; five times in the case of the 15-month duration.
To judge by records broken, this drought is by far the worst at Manilla since readings began (1883).

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, as at the end of February 2020, 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

January 2020: still 5 drought records

Rainfall status Dec-19, Jan-20

Changing shortages

January rainfall of 46.8 mm further reduced short-term shortages, bringing the 9-month total (212 mm) out of the “extreme shortage” class. Most longer-duration totals remained in that class, however.

Fewer record low rainfalls

By December 2019, there had been 10 new record low rainfalls. Records were set not only for 12-months duration, but for every one of the 9 chosen durations from 24-months to 96-months. In January 2020 there were only 5 new records, although there were 4 2nd-lowest values that also plotted on the 0.1th percentile line. The 5 new records were:

36-months duration: 1098 mm;
48-months duration: 11775 mm;
60-months duration: 2384 mm;
84-months duration: 3419 mm;
96-months duration: 4132 mm.

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, as at the end of January 2020, 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

December 2019: 10 new drought records

Rainfall status Nov-Dec 2019

Changing shortages

December rainfall of 19.6 mm, added to November rainfall of 40.2 mm, reduced the shortages for durations up to six months, but it did not prevent the drought becoming worse at nearly all longer durations. The shortage was extreme (1st percentile) at every duration beyond 6-months, except at 120-, and 144-months (severe shortage) and at 360-months (serious shortage).Although the 360-month total of 18,596 mm, being at the 10th percentile, is merely a “serious” shortage, this is the lowest 360-month rainfall total since 1952!

Record low rainfalls

New record low rainfall totals were set in December 2019 as follows:

12-months duration: 255 mm;
24-months duration: 582 mm;
30-months duration: 791 mm;
36-months duration: 1099 mm;
42-months duration: 1477 mm;
48-months duration: 1833 mm;
60-months duration: 2455 mm;
72-months duration: 2901 mm;
84-months duration: 3477 mm;
96-months duration: 4146 mm.

For most of these durations, the record had already been broken several times in this drought. However, three of these records had stood for over a century:

42-month duration: 1477 mm beats (by 43 mm) the record of 1520 mm set in September 1914;
48-month duration: 1833 mm beats (by 3 mm) the record of 1836 mm set in February 1915;
60-month duration: 2455 mm beats (by 11 mm) the record of 2466 mm set in February 1916.

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, as at the end of November 2019, 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

Rainfalls: 8 in the 0.1th percentile

Rainfall status October November 2019

Normal rainfall in November

Rainfall in November 2019 (40.2 mm) was near normal. That reduced shortages at durations from 2-months to 5-months. Otherwise it had little effect: fifteen of twenty longer durations remained extreme shortages.

Values plotted in the 0.1th percentile

For simplicity, the bottom line is labelled with the 0.1th percentile value, and percentile values below 0.1% are plotted on the line. As there are 1600 months of record, both the 2nd-driest month (percentile value 0.063%) and the driest month, (percentile value 0.000%, by convention), which would plot below the line, are plotted on it.
Driest records have again been broken at durations of 12-months (270 mm), 24-months (611 mm), 30-months (834 mm), 72-months (2927 mm), and 96-months (4205 mm). The 96-month record had stood at 4405 mm since November 1919.
A value that equals an earlier record occurs at 84-months (3555 mm).
Values that are 2nd-driest occur at 36-months (1129 mm) and at 240-months (11816 mm). The 240-month (20-year) total is now only 50 mm more than the lowest-ever value of 11766 mm set in February 1931.

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, as at the end of October 2019, 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