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.


Notes:

January data points are marked by squares.

Smoothing

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.

November 2018 began hot

A King Parrot feeding in a Hopbush

King Parrot in Hop Bush

The month began hot, with the weekly temperature more than six degrees above normal. On the 6th, the maximum reached 39.4° after a warm overnight low of 22.1°. However, rain brought a maximum of only 21.5° on the 8th. In the rest of the month temperatures were near normal. Just one morning (the 24th) had an exceptionally low dew point that was 14° below normal.
There were eight rain days, with the highest reading 17.2 mm, on the 22nd.

Weather log November 2018

Comparing November months

Although the month began so hot, the average temperature (22.7°) was only 1° above normal, and not nearly as high as in November 2014 (25.4°) or November 2009 (26.0°).
Despite the continuing drought, the only indicator showing low moisture was the early morning dew point (7.3°). There was quite a lot of cloud (43%) and a rather narrow daily temperature range (14.4°).
The rainfall total of 50.2 mm (estimated) is at the 36th percentile for November, somewhat below the average (67 mm).
I have reported the drought in another post.

Climate in November 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.  The record was again defective in November 2018. No 9 am readings were recorded. 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 November 2018

Not So Moist

3-year trends to November 2018

November raw anomaly data (orange)

In November 2018, the top four graphs show that raw values of moisture anomalies moved up away from the moist values of October, but not as far as earlier drought values.
For temperature anomalies, daily maximum and subsoil rose again, while, daily minimum fell from its extremely high value

 Fully smoothed data (red)

At this time, Manilla was entering an extreme drought. Each of the smoothed climate anomalies shown on these graphs contributed to the drought to some degree, and with more or less lag.

By May 2018, the last date for which data can be fully smoothed (as described below), most variables had not yet peaked in their contribution. Several more months of data will reveal the complete cycle into and out of drought.
The anomaly of daily maximum temperature (x-axis, all graphs) had already peaked in March 2018. (In the 2002 drought daily maximum temperature had peaked after the peak of minimum rainfall, not before.)
In May 2018 the rainfall anomaly was still becoming more negative, to a record low value of minus 28.3 mm . June and July rainfall anomalies seemed likely to be similar after smoothing.
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 winter of 2017. It had changed little since, and seemed likely to peak in June 2018 without approaching the record 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 rising rapidly in May 2018, and seemed likely to peak about July, lagging four months behind the daily maximum temperature anomaly.


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.

November Drought Gets Longer

In November 2018, the drought faded in the short term, but became worse in the long term.

Rainfall Oct Nov 2018 Manilla

Graph of Rainfall Shortages

This graph shows all the present rainfall shortages at Manilla, short term and long term, in terms of percentile values. The latest values, as at the end of October, are shown by a black line with black circles. Those from one month earlier, at the end of October, are shown by a thinner line with smaller white circles.

Changes this month

November rainfall was almost normal at 50.2 mm, further raising the totals for 2, 3, 4, and 5 months, so they did not qualify as serious shortages. The 6-month total of 156 mm qualified as a serious shortage.
The remaining extreme shortages were at 9 months (201 mm) and 18 months (564 mm).

Worsening long-term shortages

Rainfall totals for periods from 72 months to 360 months (6 years to 30 years) are now all below normal. In decades before September 2017 those totals had been normal. (See the September 2017 plot on the graph in this earlier post.)

Three of the current data points are far below normal. The 7-year total (3935 mm) is a severe (almost extreme) shortage, not seen since 1946. The 120-month (10-year) total (5986 mm) is a serious shortage, not seen since 1967. Similarly, the 240-month (20-year) total is a serious shortage, not seen since 1949.
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”.

The 2002 drought contour chart

Contour chart 2002 drought at Manilla NSW

The 2002 drought at Manilla was a failure of winter rainfall. [See Note below: “Manilla’s rainfall seasonality”.]

The top line of this contour chart shows that monthly rainfall shortages occurred in all the six months of winter rainfall dominance (April to September) of 2002. Shortages in May and July were severe, below the 5th percentile. In the summer rainfall months (October to March) that preceded and followed, rainfall was near or above normal. [See Note below: “Classes of rainfall shortage”.]

Lower down the contour chart, rainfall shortages of longer duration are shown. For droughts of 3 months duration, the rainfall shortage was extreme (1st percentile) by July 2002, as it included the serious shortage of May as well as that of July. In the same way, one sees extreme 6-month shortages in September and October, as all the monthly rainfall shortages since March added up.

By November 2002, one sees extreme droughts of 9 months and 12 months duration. The 9-month drought incorporated the consecutive months of below-normal rainfall from March to November. The extreme 12-month drought (307 mm) that was evident in November 2002 began earlier, with below-normal rainfalls in December 2001 and January 2002. That was the fourth driest 12-month period on record, after October 1965 (288 mm), August 1946 (302 mm) and November 1965 (304 mm).

The 2002 drought had no extreme rainfall shortages longer than 12 months. There were, however, some severe shortages of 18 months duration and some serious shortages of 24 months duration, due to some low rainfalls in the previous winter (2001).

By April 2003, hardly any serious rainfall shortages due to the 2002 drought remained. [See Note below: “Limitations of this analysis”]

More about the 2002 drought

Graph of monthly percentile rainfall in a droughtAnother approach to describing this 2002 drought is in the post “The 2002 rainfall shortages at Manilla”. That post has a graph showing selected monthly profiles of percentile values. It also links to two earlier posts with graphs of smoothed values of climatic anomalies.

The 2018 Drought

Drought 2018 contour chartA similar contour plot for the drought of 2018 reveals similarities and differences.


Note: Classes of rainfall shortage

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