2019-20 summer hot and moist

Sef-sown senna plants

Pepper-leaf Senna

Through December and January, this summer had a series of heat waves perhaps worse than those of the previous two summers, and rainfall and humidity were low. Similar droughty weather elsewhere brought catastrophic bushfires.
On the 3rd of February the weather changed dramatically. Heat waves were replaced by spells of cool or normal temperature, with high humidity, overcast days, and rain. Up to that date, cool spells had not occurred since November 2018, 15 months earlier. During those 15 months, regardless of the season, the weekly mean temperature often rose several degrees above normal, but never fell below normal.
Coincidentally, there were 14 rain days in both the hot-dry part of the season (65 days) and in the cool-wet part (26 days).

Weather log summer 2019-20

Seasonal average or total figures for this summer mean little because of the climatic break from 3 February.
Mean temperatures (max, mean, min) were close to the records set in the summers of 2017 and 2019, which they would have exceeded if February had not become cooler. Subsoil temperature remained normal.
In summer 2018-19, two of the moisture measures (daily temperature range and cloudiness) had been near normal, while rainfall and dew point had been low. Now, in 2019-20, rainfall and dew point were higher, making all four moisture measures normal.
The summer rainfall total of 232 mm is at the 55th percentile, very close to the average (227 mm).

Manilla summer climate


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. I have used it since 20 July, when the Museum gauge began recording again.  Unfortunately, the gauge failed during this season (25/02/2020 ). Pending repair, I am using my own gauge. My estimates of early morning dew point have become anomalously low. From 1 August 2019, I use values taken from Tamworth Airport graphs at the time of minimum temperature.
All other data, including subsoil at 750 mm, are from 3 Monash Street, Manilla.

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

2019 new hottest and driest year

At Manilla, NSW, in the twenty years from 2000, the year 2019 was the hottest and the driest, overtaking the year 2018.

Climate logs Manilla 20-years

Climate records kept at 3 Monash Street, Manilla from April 1999 yield these eight graphs of climate variables. The graphs on the left (red) show heat and those on the right (blue) show moisture.
These graphs show the figures for calendar years, not for seasons.
In general, the temperatures in this 20-year record rose, with a pause between 2004 and 2012. Moisture peaked about 2010.
At Manilla, a sudden rise in temperature and fall in rainfall happened after 2017, having been much slower before that.
Dashed horizontal lines mark the normals for the decade from April 1999.

Left column graphs (red)

Yearly Mean Maximum Screen Temperatures

Day temperatures are shown by the mean maximum temperature in the Gill-type thermometer screen. The year 2019, at 27.91°, had the hottest days by far. The year 2018 had 27.13°, and 2002 and 2014 were almost as warm.The coldest days were in 2008 (24.57°) and 2010 (24.60°), followed by 2001 and 2011.
The 4th-order trend line shows a minimum about 2010, followed by a rapid rise.

Yearly Mean Screen Temperatures

This graph shows warmth in general, as in the study of global warming. Daily maximum and daily minimum temperatures are averaged. The year 2019 was the warmest (19.83°), followed by 2018, 2014, and 2009. The coolest year in this century was 2008 (17.19°), followed by 2001, 2011, and 2012.
The 4th-order trend line shows near-constant temperature from 2000 to 2011, followed by a rapid rise.

Yearly Minimum Screen Temperatures

Night temperatures are shown by the mean minimum temperature in the thermometer screen. While 2018 had not had very warm nights, 2019, at 11.75°, had warmest nights as well as days. The next warmest were in 2014, 2010 and 2009. Years with nights cooler than 10° on average were 2012, 2008, 2006 and 2001.
The 4th-order trend line shows a rise from 2000 to 2008, then near-constant temperature to 2014, followed by a rapid rise.

Yearly Subsoil Temperatures

Yearly temperatures in the subsoil (at 750 mm depth) hardly related at all to air temperatures read in the Gill Screen. The best match is in 2008, when the subsoil temperature was lowest (19.00°), as were the screen mean (17.19°) and the screen maximum (24.57°).
[Note that world temperature was low late in 2007.]
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

“Novel graphs for rainfall shortages”

I display my drought poster

Garry’s drought poster

Drought poster for conference

Grasslands Conference Poster Display

A conference paper about drought graphs

This blog “Climate by Surly” has analyses of the current drought at Manilla, mainly in the form of graphs. I was invited to present these findings as a “Poster Paper” at a conference of the Grassland Society of NSW at Gunnedah in July 2019. The poster itself is shown in the photo and the reduced image above.

The paper

The paper is published in two parts: the colour poster shown above, and four pages of text and figures. Both have the title “Novel graphs show extreme rainfall shortages”.
The point of my paper was that these novel graphs bring out features of the current drought at Manilla in a way that could be applied at other times and places.
Because the paper is brief, I have referred the reader to further information in posts in this blog. The construction of each of the three kinds of graph is fully explained in the posts that I linked:
/2019/03/31/march-rain-leaves-drought-extreme/
/2019/04/09/rainfall-shortage-sequence-03-2019/
/2019/04/15/rainfall-shortage-history-manilla/
/2019/04/16/rainfall-shortage-jan-2000-mar-2019/

The complete reference to the paper is:
Speight JG (2019) Novel graphs show extreme rainfall shortages. In
‘Proceedings of the 31st Conference of the Grassland Society of NSW Inc.’ (Eds SR Murphy, SP Boschma, and M Simpson). pp. 36-39. (Grassland Society of NSW Inc., Orange).

The text can be accessed here as a pdf:

https://climatebysurly.files.wordpress.com/2019/12/6-2019-grassland-conf-proc-speight-pp35-39-web-ver.pdf

The paper will become accessible on the website of the Grassland Society of NSW.

The Poster on display

Thanks to the generosity and interest of the proprieters, the original of the poster can be seen at Molly May’s Coffee Shop in the main street of Manilla.

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