November 2019: one warm week

Bushfire smoke

Manilla View 18-11-2019

One week, beginning on the 20th, was 5.4° warmer than normal. The night of the 22nd did not get cooler than 24.0°, making it the 5th warmest November night in this century. (One night in November 2009 had been 27.8°, the warmest night of any month.) In other weeks of this month, temperatures were normal.
Most days were dry and sunny. However, days early and late in the month were cloudy, with high dew points and narrow daily temperature ranges. Six of these days had rain, with the highest reading 16.4 mm on the 4th.
Smoke from coastal bushfires reduced visibility from the 17th to the 29th. On the 18th, visibility was only one kilometre, as shown in the photo.

November 2019 weather log

Comparing November months

Although this month was warm. other November months have been warmer: in 2002, 2009, 2012, and 2014. All of these had especially warm days. While days this month averaged 31.8°, days in November 2009 averaged 34.3°. The coolest recent November was in 2017.
This was a dry month but, by various measures, not as dry as in 2002, 2009, 2014 or 2016. The rainfall total of 40.2 mm is in the 27th percentile.

November 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 November 2019

November just like October

3-year trends to November 2019

November raw anomaly data (orange)

Temperatures

Daily maximum temperature anomaly (all x-axes): now three degrees above normal.
Daily minimum temperature anomaly (lower left): remains high.
Subsoil temperature anomaly (lower right): still near normal.

Moistures (moist is at the bottom)

Rainfall anomaly (upper left): still very low.
Cloudiness anomaly (upper right): still normal.
Dew point anomaly (middle left): still rather low.
Daily temperature range anomaly (middle right): has risen back to high.

 Latest fully smoothed data (red) includes autumn 2019

Smoothed anomaly values are now available for the autumn (MAM) of 2019. Generally they show a steady retreat from the extreme (smoothed) anomaly values of January. Rainfall anomaly rose, while daily maximum temperature anomaly fell. Daily minimum temperature anomaly fell rapidly, and subsoil temperature anomaly rose rapidly. Cloudiness and dew point changed little. Temperature range anomaly, which had decreased slowly to January, began to increase again.


Notes:

January data points are marked by squares.

Smoothing Continue reading

How much rainfall is now lost?

Rainfall deficits in mm at Manilla NSW, Oct 2019

This graph shows the total rainfall shortage in this drought at Manilla NSW. It uses the same rainfall figures as in the October Rainfall Status graph, that is, the rainfall totals for up to 360 months. In this case, I have subtracted from them the normal rainfall totals. That shows the rainfall deficit: how much less rainfall we have had than we normally would.

Generally a 1-year deficit

In many cases, the shortage now is about 650 mm, or one year of normal rainfall. This is true when calculated for 24-months and for several other durations including 360-months. In broad terms, this drought has left Manilla about one year short of rain.

Deficits are smaller at short durations.

A one-year deficit could occur at a duration of 12-months only if there were no rain. A curve on the graph shows “No rain at all”. A second curve is labelled “50% of normal Rain”. These October data show that the rainfall totals for durations below 24-months are around 30% of normal.

Deficits larger than 650 mm occur at some long durations

There are three dips in the curve where deficits are greater than one year of rainfall.

  1. The 3-year deficit is now 820 mm, due to very low rainfall in the last six months. Such values may yet appear at other durations.
  2. The 7-year deficit is now 920 mm. This deficit is due to the inclusion of severe rainfall shortages of 12-month to 30-month duration in 2013 and 2014. These appear on this drought duration graph, but were scarcely noticed at the time.
  3. The 20-year deficit is now 1100 mm. The 650 mm deficit due to the current drought is supplemented by deficits of some 200 mm carried forward from both the 2013-14 shortages (above) and the extreme 12-month shortage of 2002.

What the deficits mean

In times of normal or excess rainfall, the whole terrain is kept supplied with water. It goes to aquifers deep underground, to shallow aquifers near streams, to stream-flow, and to the soil and plants. In general, the longer the duration of normal or excess rainfall, the larger the reservoirs, both underground and on the surface, that can be filled.
The present deficit of one year of rainfall must have drawn down all the reserves of water in the terrain. The empty state of the Keepit Dam (0.8%) is an obvious result, but all other reserves must have fallen.

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” (red), but merely “severe” (grey) 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 (red). 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 1902 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.