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 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.]

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.


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