Tag Archives: drought

3-year trends to June 2018

Posted in 3-year climate trends, Manilla NSW by

Now in drought

Three year trends to June 2018

June raw anomaly data (orange)

The raw rainfall anomaly for June 2018 was very low (high on the graph), as was that of the month before. This placed June in drought, although the other moisture indicators were nearer to normal. Daily maximum and minimum temperatures were also not far above normal, but subsoil temperature was very high.

 Fully smoothed data (red)

The last fully-smoothed data is for December 2017. All variables, except subsoil temperature, continued trends set in the spring.

Daily maximum temperature anomaly approached a record high value.
Rainfall anomaly approached a record low value.
Cloudiness was static near its normal maximum.
Dew point anomaly was low but slowly rising.
Daily temperature range anomaly was high but slowly falling.
Daily minimum temperature anomaly was high and rising.
Subsoil temperature anomaly, which had been falling, began to rise.

Note:

Fully smoothed data – Gaussian smoothing with half-width 6 months – are plotted in red, partly smoothed data uncoloured, and raw data for the last data point in orange. January data points are marked by squares.
Blue diamonds and the dashed blue rectangle show the extreme values in the fully smoothed data record since September 1999.

Normal values are based on averages for the decade from March 1999.* They appear on these graphs as a turquoise (turquoise) circle at the origin (0,0). A range of anomalies called “normal” is shown by a dashed rectangle in aqua (aqua). For values in degrees, the assigned normal range is +/-0.7°; for cloudiness, +/-7%; for monthly rainfall, +/-14 mm.

 * Normal values for rainfall are based on averages for the 125 years beginning 1883.

Rainfall Shortages up to June 2018

Posted in Australian Climate, Climate events, Manilla NSW by

Rainfall shortage Manilla, June 2018

Since the twelve-month drought of 2002, Manilla has been free from extreme rainfall shortage until now. Such a long gap between extreme droughts has not been seen here before. [See Note below: Dry May 2006.]

Rainfall shortages now

On this graph the black line with black squares shows Manilla rainfall shortages at the end of June 2018. Shortages are shown for short terms down to one month, and for long terms up to 360 months (30 years).

[Shortages at the end of May are shown in a previous post.]

[A graph showing shortages at the end of July is in a later post: “Drought Fifth Month; July 2018”.]

Extreme shortages

Three extreme rainfall shortages have now developed, all below the 1st percentile rank:
Total for two months (May and June): 6 mm;
Total for three months (April, May and June): 24 mm;
Total for four months (March, April, May and June): 50 mm.

Severe shortages

There were five severe shortages in rainfall totals as follows:
Total for six months: 141 mm, at the 4th percentile;
Total for twelve months: 350 mm, at the 2nd percentile;
Total for fifteen months: 492 mm, at the 3rd percentile;
Total for sixty months: 2672 mm, at the 4th percentile;
Total for seventy-two months: 3317 mm, at the 4th percentile.

Serious shortages

Some other rainfall shortages were not severe, but serious:
Total for one month: 5.2 mm, at the 7th percentile;
Total for five months: 120 mm, at the 6th percentile;
Total for nine months: 464 mm, at the 10th percentile;
Total for eighteen months: 658 mm, at the 6th percentile.

Comparing June 2018 with the month before

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A drought has begun

Posted in Australian Climate, Climate events, Manilla NSW, Rainfall from 1883 by

A year ago, I showed that Manilla was far from being in a drought. That is not true now. There are severe shortages of rain.

Rainfall status at Manilla, September 2016 and September 2017.

The first graph has rainfall totals up the left margin. They are not expressed in millimetres but as percentile values, Along the bottom margin is the number of months included in calculating each rainfall total.

On the graph, I have compared the rainfall situation today, September 2017, plotted in red with that of September 2016, plotted in grey. Much has changed.

Take, for example, the 12-month (one-year) rainfall total. Rainfall totals for 12 month periods are directly above the value “12” at the bottom of the graph, near the label “Number of Months included”. In data for the month of September 2016 (grey), the 12-month total (actually 802 mm) had been at the 80th percentile, which was very high. In up-to-date data for the month of September 2017 (red), the 12-month total (actually 484 mm) is at the 17th percentile, which is very low.
Although rainfall totals for  periods longer than 12 months have not fallen so much, nearly all of them have fallen. Three that have not are those for 30 months, 36 months and 42 months. They were already low, due to including in them some months of low rainfall several years ago, in 2013 and 2014.

So far, real shortages have occurred mainly within the last 12 months. Beyond that, the two-year rainfall total of 1285 mm, for example, is still near normal, plotting at the 48th percentile.

The second graph shows in detail how shortages that are serious or severe have developed during the last six months. These were the monthly rainfall amounts, with the normal amounts in brackets:

April: 24.0 mm (39.3);
May: 55.6 mm (40.3);
June: 62.8 mm (44.3);
July: 13.2 mm (41.4);
August: 13.8 mm (39.5);
September: 5.5 mm (41.2).

As a result, the current situation is as shown below. There are already severe rainfall shortages, at the 2nd or 3rd percentile, in the two-month and three-month totals to date. There are also serious shortages, at the 8th and 9th percentiles, in the four-month and six-month totals to date.

Drought status at Manilla in September 2017

I will update these graphs each month to show how the situation changes.

[Monthly updates were not posted because serious rainfall shortages did not occur in any following months up to March 2018. The next post with a graph and analysis like this one was “Rainfall Shortages up to May 2018” of 15/6/2018.]

[This 2018-19 drought became the worst ever experienced at Manilla. Records for the lowest-ever rainfall totals were broken repeatedly. See, for example (June 2019)  “June breaks more drought records”.]

Is There Any Drought Now?

Posted in Australian Climate, Manilla NSW, Rainfall from 1883 by

No. In Manilla just now, there is no drought of any kind: not a short drought, a medium-length drought, or a long drought; not an extreme drought, a severe drought, or even just a serious drought.

A new comprehensive graph of the severity of drought at one site.

In this graph, each line of data points is for one particular month. The middle line, joining the red squares, shows the whole rainfall drought situation for last month: September 2016.
This is a new kind of graph. (See Note 1 below.) It can show how severe a drought is, not only during the last month or two, but during the last year, and during the last many years. That is a lot of information.

How to read the graph

A month of extreme drought would have data points very low down on the graph. The scale on the left side is amount of rainfall. It must be a “percentile” value. For example: if the amount of rain that fell is just more than has been seen in the driest 5% of all months, it has a value in the 5th percentile. (See Note 2 below.)

Along the top and bottom of the graph I have plotted a number of months.
The number does not show time passing. It shows the number of months I included in a calculation. For each month on record I did many calculations. I added up the total rainfall for:
* the month itself;
* two months including the previous month;
* three months including the month before that;
* … and so on.
I found the totals for larger groups of months extending back as far as 360 months (30 years).
Using all these rainfall totals, I calculated percentile values to plot on the graph. For example, for groups of 12 months, all groups of 12 consecutive months are compared with each other, to find the percentile value of the 12-month period ending in a given month. (See Note 3 below.)

Which months had the most drought and least drought?

The worst drought there could ever have been would be one with data points along the bottom line of the graph. In such a disastrous month, all the rainfall totals would be the lowest on record, not just the one-month total, but also the two-month total and so on up to the 360-month total. Every one of them would be the lowest total on record. It has never been as bad as that.
The “best” time, in terms of being free of drought, would be a month with all its data points along the top edge of the graph. For that month, every rainfall total, for a short period or a long period, would be the wettest on record.
From the Manilla rainfall record, I have chosen to display the most drought and the least drought that actually occurred.

The most drought: August 1946

The month of August 1946 had no rain. Of course, that was the lowest rainfall for any August month (One among 13 months on record that had no rain.). As a result, the percentile rank for that month’s rainfall is zero. Most totals for groups of any number of months ending in August 1946 are also on the “zero-th” percentile, that is, the lowest on record. Thus, it was an extreme drought in the short term, medium term and long term.
For this month, percentile values that are above the third percentile occur in the totals for 48, 60, and 72 months, as shown. These figures, while not extremely low, were still well below normal (Normal is the 50th percentile.). They occur because these totals include some wet months in 1940, 1941, and 1942.

The least drought: March 1894

March 1894, with 295 mm of rain, was one of the the wettest months ever, ensuring a 100th percentile value. The rainfall totals for groups of months ending in that month included six other “wettest ever” values, and all other groups of months were also very wet. No group of months was below the 95th percentile. (See Note 4 below.)

Current drought situation (September 2016)

This month’s rainfall total of 122.4 mm puts it in the 92nd percentile of all monthly rainfall values, far above the median value marked as “normal” on the graph. The 2-month rainfall total (203 mm), and the 4-month rainfall total (350 mm) are almost as high, each in the 90th percentile.
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Manilla’s Droughts, 1884 to 1916

Posted in Australian Climate, Climate Change, Manilla NSW, Rainfall from 1883 by

Graphical log of droughts, 1884 to 1916

The catastrophic droughts in 1902 and 1912-16 were quite different.

In the years before 1917 shown here, Manilla had several times of extreme drought. They came in 1888, 1895, 1902, and in a cluster that began in 1912.
(1.) The 1888 extreme droughts were of 2-, 3-, 4-, 5-, 6- and 9-month duration. The 2-month event was in August, and other events came later as they became longer, until the 9-month event came in December (having begun in April).
(2.) In 1895, drought was extreme only for durations of 5-months (June) and 6-months (July and August). Although droughts of 2-, 3-, 4-, and 9-month duration also occurred, they were not extreme, but merely “severe”.
(3.) Manilla’s 1902 (“Federation”) drought was phenomenal. Extreme droughts of nearly all durations from 2 months through to 96 months occurred (and ended) at practically the same time. The 2-month event plots at May 1902. The 96-month extreme drought plots at February-March 1903. None of the drought events around 1902 extended far into 1903; all ceased abruptly. The rainfall shortages began earlier according to a simple pattern; the longer the duration of the extreme event, the earlier it began. The 1902 extreme 1-year drought began in September 1901, and the extreme 8-year drought began in 1895.
(4.) The cluster of drought events extending through 1912 and 1916 was as bad as the events of 1902, but quite different. Merely “severe” short-duration events began in April 1911. Events of increasing duration came at later dates, forming a smooth curve on the graph. Beyond 12-month duration, and up to 72-month duration, there were extreme events at nearly all classes of duration. By the 72-month duration, the date of plotting had drifted forward in time to January-July 1916. The beginning of these 72-month events would have been during Continue reading →