One- and two-year droughts recur in January 2019

Drought contour plot to Jan 2019

This contour plot shows the progress of the extreme drought at Manilla up to January 2019. Colours show rainfall shortages as percentiles. Dates plot along the top, and durations down the side.

One month rainfall totals (on the top row)

By January 2019, there had been six months without serious monthly rainfall shortages. The months of serious rainfall shortage (light brown) were earlier, in May, June and July 2018. The only other month with such low rainfall was September 2017.

Droughts lasting less than one year (rows 2, 3, 4, 5, 6, 9)

As the effects of low monthly rainfall added up, extreme droughts appeared (dark brown). That is, rainfall totals below the 1st percentile. (They are the lowest rainfall totals, that have occurred in less than 1% of the historical record.)
By June 2018, the 2-month and 3-month totals were already extreme shortages. Similarly, by July, the 3-month, 4-month, and 5-month totals were extreme shortages. By September 2018, extreme shortages extended as far as the 9-month total. That total, adding up the nine months from January to September 2018, included only one month (February) that had rainfall above normal.
In these durations of less than one year, extreme droughts were rare after September 2018. Because the last six months had no serious monthly shortages, the final month (January) includes no serious shortages for durations from 2 months up to 6 months.

Droughts of 1 year to 2 year duration (rows 12, 15, 18, 24)

By August 2018, an extreme 15-month drought appeared. That 15-month total then included not only the dry months of winter 2018, but also the dry month of September 2017. By September 2018, the 15-month total became the driest on record (400 mm). By October all four droughts in this group (12-, 15-, 18-, and 24-month droughts) were extreme. This became true again in January 2019. By that date, some of the dry months of 2017 were no longer included, but dry months in the current summer replaced them in the total.

Related graphs

A similar contour plot with data to October 2018 is here.

A line graph of the rainfall status for January 2019 reveals that extreme shortages also exist now at the much longer durations of six years and seven years that are not included in this contour plot.


The following notes include:

Classes of rainfall shortage

Rainfall rate versus percentile rank

Limitations of this analysis

Note: Classes of rainfall shortage

Continue reading

January 2019 very hot

Sun sets through gum tree

Eucalypt Silhouette

Weekly temperatures were high all month, peaking at 6.4° above normal on the 17th and never less than 3.4° above normal. Seven days had peak temperature over 40° (fewer than the nine in February 2017). Only one day was cooler than normal, while no nights were.
There were four rain days, with 18 mm recorded on the 21st.

Graphical log for January 2019

Comparing January months

January 2019 was very hot: more than two degrees hotter than any recent month. Mean temperatures were far above the normal January temperatures for this station (means for the decade from March 1999):

Mean Maximum: 38.4°, above normal by 4.6°.
Mean average: 30.8°, above normal by 4.8°.
Mean minimum: 23.2°, above normal by 5.2°.

Manilla was not the only hot place. Australia-wide, this was the warmest January on record.

Apart from high air temperatures, Manilla’s climate was near normal. Even the subsoil temperature was normal. So were the cloudiness, dew point and daily temperature range.
The rainfall of 25.0 mm was at the 15th percentile, far below the average (87 mm). I will report the on-going drought in another post.

Climate for January months

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.  Since no 9 am readings have been recorded since August, I have substituted my non-standard gauge readings for all days.
All other data, including subsoil at 750 mm, are from 3 Monash Street, Manilla.

2018 hottest and driest

In the nineteen years 2000 to 2018, this last year was the hottest and the driest.

Climate logs 19 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. They do not show hot summers or cold winters. In particular, each summer spans two calendar years.
In general, the temperatures in this 19-year record rose, with a pause between 2004 and 2012. Moisture peaked about 2010.

Day Temperatures

Daily max temp, 19 years

Day temperatures are shown by the mean maximum temperature in the thermometer screen. The year 2018, at 27.13°, had the hottest days by far. Four other years with hot days were widely spread: 2002, 2009, 2014, and 2017. The coldest days were in 2008 (24.57°) and 2010 (24.60°), followed by 2001 and 2011.

Average Temperatures

Daily Mean Temp, 19 years.

This graph shows warmth in general, as is done in the study of global warming. For each day, the daily maximum and daily minimum temperatures are averaged. Then these values are averaged for each year. The year 2018 was the warmest (19.11°), but 2017 was only fourth, beaten by 2014 and 2009. The coolest year in this century was 2008 (17.19°), followed by 2001, 2011, and 2012.

Night temperatures

Daily min temp, 19 years

Night temperatures are shown by the mean minimum temperature in the thermometer screen. The year 2018 , at 11.09°, had only the fourth warmest nights. The warmest were in 2014, at 11.34°, followed by 2010 and 2009. Years with nights cooler than 10° on average were 2012, 2008, 2006 and 2001.

Subsoil temperatures

Continue reading

December 2018 dry and hot

Tropidoderus stick insect

Stick Insect

Weekly temperatures, which began normal, then remained high all month, peaking
around four degrees above normal on the 18th and again on the 29th. Only a few days or nights were cooler than normal.
There were six rain days, grouped around the 16th, which had 25 mm. Earlier and later times had sunny skies and low dew points.

Graphical log of weather December 2018

Comparing December months

Remarkably, the three mean temperatures this month are practically the same as those of both December 2017 and December 2016. They are higher, but by no more than 0.2°, near the limit that can be read on my thermometers. The mean daily maximum of 33.9° and the mean daily mean of 26.1° are the hottest for December in this record from 1999. (The mean daily minimum of 18.3° was exceeded by 18.6° in December 2009.)
This was one of the most sunny December months. The percentage of cloudy mornings (19.4%) was the same as in December 2006, but higher than in 2002 or 2005 (both 16.1%).
The rainfall of 34.5 mm is at the 22nd percentile, far below the average (74 mm). Lower rainfall totals occurred in December of 2001 (34 mm) and 2006 (19 mm). I have reported the on-going drought in another post.

Climate in December months

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.  Since no 9 am readings have been recorded since August, I have substituted my non-standard gauge readings for all days.
All other data, including subsoil at 750 mm, are from 3 Monash Street, Manilla.

3-year trends to December 2018

December hot and dry

3-year trends to December 2018

December raw anomaly data (orange)

In December 2018, the top two graphs show that rainfall was low and skies sunny.
The daily maximum temperature (x-axes, all graphs) and daily minimum temperature (lower left graph) were extremely high, but the subsoil was cool. Dew point and daily temperature range were near normal.

 Fully smoothed data (red)

Climate anomaly data when smoothed in this way do not show changes from month to month, but only those cycles that last for a year or more. The smoothed data identify the month when a peak occurs in a cycle .

By June 2018, the last date for which data can be fully smoothed (as described below), some variables had already peaked in their contribution to the current extreme drought.

The anomaly of daily maximum temperature (x-axis, all graphs) had peaked in March 2018. Two months later, in May 2018, the rainfall anomaly peaked (negative) to a 21st-century record low value of minus 28.3 mm. (In the 2002 drought daily maximum temperature had not peaked until after the peak of minimum rainfall.)
By June, cloudiness was decreasing towards a minimum (perhaps in August 2018) without becoming much less cloudy than normal. Dew point anomaly was still decreasing, and seemed likely to reach a record low value about August.
The anomaly of daily temperature range had been at a (high) level characteristic of drought since the previous winter (2017). It had changed little, and peaked in May 2018 without getting near the record high value of July 2002.
The anomaly of daily minimum temperature has a cryptic relation to drought. In this case, the value peaked sharply in February 2018 before falling rapidly. It may have reached a minimum about August 2018.
The anomaly of subsoil temperature was high in June 2018, and seemed likely to peak about July, lagging four months behind the daily maximum temperature anomaly.


January data points are marked by squares.


Smoothing uses Gaussian functions.
For fully smoothed data the function has a Standard Deviation of 2.5 months, it spans 13 monthly data points, and has a half-width of 6 months, which suppresses cycles shorter than 12 months. For partly smoothed data, the span of the function is reduced to 11 months, 9 months and so on.

Fully smoothed data points are plotted in red, partly smoothed data uncoloured, and raw data for the last data point in orange.

Limiting values

Blue diamonds and the dashed blue rectangle show the extreme values in the fully smoothed data record since September 1999.

Normal values

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.

Driest 18 months in 50 years

In December 2018, droughts of long duration got worse.

Rainfall shortage November-December 2018

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 December, are shown by a black line with black circles. Those from one month earlier, at the end of November, are shown by a thinner line with smaller white circles.

Changes this month

Short-term shortages

Although December rainfall (34.5 mm) was below normal, it was enough to keep the totals for 2, 3, 4, and 5 months above the level of “serious shortage”. Because the 6-month total rose to 186 mm, it too did not count as a serious shortage.

Extreme shortages

There were extreme shortages (1st percentile) at durations of 9 months (210 mm), 12 months (327 mm), 18 months (536 mm) and 7 years (3891 mm). The 18-month shortage was the most extreme, being the fifth lowest in history, after four lower values in 1966 (the lowest: 514 mm). The extreme 7-year shortage that has now appeared is lower than any since 1942.

Worsening long-term shortages

This drought brings worsening long-term rainfall shortages. Among the 14 selected durations longer than 2 years that are shown here, 10 of them are now serious shortages (10th percentile) or worse.
As well as the extreme 7-year shortage, two serious shortages that appeared in November are now worse: the 10 year total fell from 5964 mm to 5944 mm, and the 20-year total fell from 12209 mm to 12200 mm. The 10-year shortfall amounts to nearly one year of rain.
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”.

Spring 2018 warm

Native vine blossoms

Wonga wonga in spring

This spring was marked by very high temperature in the first week of November. Both days and nights were about five degrees above normal, as hot as expected in mid-summer. Less extreme warmth also occurred in the second half of October and in the second week of September. Periods of very dry air (marked “ARID”) came in mid-September, late November, and at the time of very high temperature.
There were 23 rain days (normally 19), but there was one rainless period of 17 days in September. No day had more than 17 mm of rain.

Weather log spring 2018

The season’s rainfall of 114 mm was at the 24th percentile, about 50 mm below average (166 mm). [The highest rainfall on this graph, spring 2016, is only 45 mm above average.] Other measures of moisture this spring (cloud, dew point, and low daily temperature range) were similar to those of spring 2017 and 2016. They were much moister than those of spring 2013.
The season was warm, with days 0.5° above average and nights 1.5° above average. Spring 2016 had been three degrees cooler. The subsoil temperature was below normal, as it was in the three previous spring seasons.

Climate for spring 2018

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. Station 55312 recorded no readings in spring 2018. I used my own readings for the whole season.

All other data, including subsoil at 750 mm, are from 3 Monash Street, Manilla.