November Drought Gets Longer

In November 2018, the drought faded in the short term, but became worse in the long term.

Rainfall Oct Nov 2018 Manilla

Graph of Rainfall Shortages

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

Changes this month

November rainfall was almost normal at 50.2 mm, further raising the totals for 2, 3, 4, and 5 months, so they did not qualify as serious shortages. The 6-month total of 156 mm qualified as a serious shortage.
The remaining extreme shortages were at 9 months (201 mm) and 18 months (564 mm).

Worsening long-term shortages

Rainfall totals for periods from 72 months to 360 months (6 years to 30 years) are now all below normal. In decades before September 2017 those totals had been normal. (See the September 2017 plot on the graph in this earlier post.)

Three of the current data points are far below normal. The 7-year total (3935 mm) is a severe (almost extreme) shortage, not seen since 1946. The 120-month (10-year) total (5986 mm) is a serious shortage, not seen since 1967. Similarly, the 240-month (20-year) total is a serious shortage, not seen since 1949.
Such long-term rainfall shortages were common early in the 20th century. They have hardly occurred since the Keepit Dam was built in 1960.

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”.

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