21stC Rain Shortage Oct ’19

Record of rainfall shortages Jan 2000 Oct 2019

Since the graph for May, the drought at Manilla has become more severe at all durations, from two months up to 240 months.

[For explanation of this graph, see below: “About drought duration graphs”.]

Shortages Jan 2000 to Oct 2019

Seasonal rain shortages recorded to October 2019 are extreme (1st percentile) in the winters of both 2018 and 2019.
For durations of 9 months up to 96 months, extreme shortages now occur at all of the durations shown . This is much worse than in May. At that time, shortages had not been “extreme”, but merely “severe” at the durations of 36-, 42-, 48-, 60-, and 96-months.
By May, “severe” shortages had already appeared at the very long durations of 120-, 150-, and 240-months. Now, there are also severe shortages at 108-months and 180-months.
The shortage at 240-months has now also become extreme. Very low rainfalls since May have dragged down the 240-month total to make it the sixth driest on record at Manilla. This links the short extreme drought of 2002  to become a part of the current drought. That would have seemed unlikely during later deluges, as in summer 2011-12.

Complete Manilla drought record to Oct 2019

Compete record updated to October

When the graph of the complete record of months of rainfall shortage at Manilla is updated to October 2019 it is clear that the current drought is one of the greatest droughts in history.
Now that an extreme rainfall shortage has appeared at 240-month (20-year) duration, along with a complete suite of extreme shortages from 2-months to 96-months, only the droughts of 1912 and 1946 are comparable. The Federation drought of 1903 may also have had a 20-year extreme shortage, but data for that duration are incomplete.


About drought duration graphs

These graphs show the onset, persistence, and breaking of episodes of extreme and severe rainfall shortage (droughts) at Manilla. The Continue reading

October: 20-year extreme shortage

Rainfall status Manilla Sep-Oct 2019

Most rainfall shortages are now extreme

The Rainfall Status graph for October 2019 at Manilla shows extreme rainfall shortages (below the 1st percentile) at most durations.
Of the 25 durations shown, 16 are now extreme shortages, and 7 are severe shortages (below the 5th percentile).
That leaves only 2 that are not far below normal: the October 1-month rainfall (21.4 mm) at the 16th percentile, and the 360-month (30-year) total (18696 mm) at the 14th percentile. Even this 30-year total is lower than any seen here since 1952.

A long-duration extreme shortage

An extreme shortage has now appeared at the very long duration of 240 months (20 years). In the 20 years since November 1999 the total rainfall was only 11893 mm – the 6th driest in history. Drier 20-year periods occurred only in the 1940’s and 1950’s.
Given that the median 20-year rainfall at Manilla is 13010 mm, this is a shortfall of 1117 mm, which is nearly two years of rainfall lost.

Only three new records this month

In this drought, rainfall totals in the 1- to 7-year range have broken records for low rainfall repeatedly. This month only three records have been broken: 24-months (615 mm), 30 months (850 mm), and 36-months (1111 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 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

3-year trends to October 2019

October hot days and nights

3-year trends to October 2019

October raw anomaly data (orange)

Temperatures

Daily maximum temperature anomaly (all x-axes): one degree above the maximum for smoothed values.
Daily minimum temperature anomaly (lower left): has jumped from very low to very high.
Subsoil temperature anomaly (lower right): back to normal again.

Moistures (moist is at the bottom)

Rainfall anomaly (upper left): extremely low.
Cloudiness anomaly (upper right): normal.
Dew point anomaly (middle left): now not very low.
Daily temperature range anomaly (middle right): has fallen from extremely high to near normal.

 Latest fully smoothed data (red), for April 2019

The latest smoothed anomaly values (April 2019) all show a further retreat from the extreme drought values of the summer of 2018-19.

Rainfall and temperature trajectory Sep2016 toFeb 2019The situation is little different from two months ago, as I discussed with an enlarged graph of temperature and rainfall anomalies in the post “Hot and dry records in January 2019”.


Notes:

January data points are marked by squares.

Smoothing Continue reading

Warm, dry October 2019

White box tree

My old E. albens.

The first week was 5 deg warmer than average, and the fourth and fifth weeks were also warm. The 7th of the month, at 37°, was the second hottest October day in this century, then the night of the 25th, at 21.3°, was the warmest October night.
Most days were sunny. Rain was recorded on the 12th (16.6 mm) and the 17th (4.4 mm).

October 2019 weather log

Comparing October months

This was the second-warmest October of the new century by all three temperature measures: daily max: 29.7°; daily mean: 21.2°; and daily min: 12.7°. The warmest had been October 2015, with 30.2°, 21.7°, and 13.1°.
It was a dry month but, by various measures, not as dry as in 2013 or 2014.
The rainfall total of 21.0 mm is in the 16th percentile, and the 20th driest on record.

October climate

Drought

I will report separately on the on-going drought that continues to break low-rainfall records at durations of 15-months and longer.


Data. A Bureau of Meteorology automatic rain gauge operates in the museum yard. From 17 March 2017, 9 am daily readings are published as Manilla Museum, Station 55312.  These reports use that rainfall data when it is available. Recording resumed on 20 July 2019.
My estimates of early morning dew point have drifted anomalously low. From August 2019, I use data from the Tamworth Airport published graphs.
All other data, including subsoil at 750 mm, are from 3 Monash Street, Manilla.

3-year trends to September 2019

September extreme and arid

3-year climate trends to September 2019

September raw anomaly data (orange)

Temperatures

Daily maximum temperature anomaly (all x-axes): near the maximum for smoothed values.
Daily minimum temperature anomaly (lower left): has rapidly fallen very low.
Subsoil temperature anomaly (lower right): near normal again.

Moistures (moist is at the bottom)

Rainfall anomaly (upper left): extremely low.
Cloudiness anomaly (upper right): normal.
Dew point anomaly (middle left): now very low (arid).
Daily temperature range anomaly (middle right): extremely high.

 Latest fully smoothed data (red), for March 2019

Latest smoothed anomaly values (March 2019) all show a retreat from the extreme drought values of the summer of 2018-19.


Notes:

January data points are marked by squares.

Smoothing Continue reading

More drought records in September 2019

Rainfall status Aug-Sep 2019 Manilla

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 September, 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 rainfalls for 15-months to 36-months

With only 1.2 mm of rain falling in September 2019, most of the rainfall totals that had been record low values in August fell further to become new records. Some of these rainfall totals had been getting lower in each of the last four months. Until 2019, these records for low rainfall had not been broken in half a century, some having been set in the great drought of 1966.
Some of the current rainfall totals are very much lower than the previous long-standing records. For example:

  • 18-month total to Sep 2019: 384 mm; to Apr 1966: 514 mm; now lower by 130 mm.
  • 30-month total to Sep 2019: 853 mm; to Oct 1966: 1078 mm; now lower by 225 mm.
  • 36-month total to Sep 2019: 1161 mm; to Jan 1947: 1333 mm; lower by 172 mm.

Record low rainfalls for 72-months and 84-months

Record low rainfalls for 72-months and 84-months, which had appeared during 2019, got steadily lower. The earlier records had stood for more than a century, (Feb, Mar 1903) but are now beaten by about 100 mm.

The latest four months

September’s low rainfall has dragged down the totals for 2-, 3-, and 4-months. The 4-month total of 22 mm is the 2nd lowest ever.

The pattern of this drought

Two features of this drought are now clear from this data:

  • It is an extreme drought of two to three-year duration: one of Manilla’s six great droughts.
  • Record-breaking rainfall shortages at 72-month and 84-month duration show that the summer droughts of 2012-13 and 2013-14 still have an effect, not compensated by the wet winter of 2016.

Table of lowest-ever rainfalls

In a post of July 2018, I tabulated the lowest-ever rainfall for selected durations up to 360 months.

I commented that such records are rarely broken, and all had stood for at least forty-six years at that date.
The current drought has now broken most of those records for durations between 12-months 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

Dry September 2019

Striped Honeyeater at the Window

Weekly average temperatures increased slightly, as is usual in September. Unusual day temperatures came early in the month. The first 30-degree day was 18 days early, on the 5th. The next day was the hottest of the month, at 31.9°. During the next 3 days the daily maximum temperature fell by 16.9° to 15.0°, the coldest day of the month. Later, temperatures stayed closer to normal. There were 4 frosts, the usual number.
At the Manilla Museum, 1.2 mm of rain was recorded on the 23rd.

Comparing September months

The last three September months have all been dry, with low dew points, wide daily temperature ranges and not much cloud. They have not been nearly as hot as September of 2013, however.
The rainfall total of 1.2 mm is the 3rd lowest September reading, after 0 mm in 1980 and 1 mm in 1925. By way of contrast, the second graph also includes the deluge of 122.4 mm in September 2016, the 4th wettest on record.

Drought

I will report separately on the on-going drought that continues to break low-rainfall records at durations of 15-months and longer.


Data. A Bureau of Meteorology automatic rain gauge operates in the museum yard. From 17 March 2017, 9 am daily readings are published as Manilla Museum, Station 55312.  These reports use that rainfall data when it is available. Recording resumed on 20 July 2019.
My estimates of early morning dew point have drifted anomalously low. From August 2019, I use data from the Tamworth Airport published graphs.
All other data, including subsoil at 750 mm, are from 3 Monash Street, Manilla.