May 2019 had the warmest nights

Keepit Dam boom, May 2019

The month began warm, with the night of the 2nd being, at 18.0°, the warmest May night of the new century. There was a second warm spell nearly four degrees above normal about the 20th.
The first frost (by my reading) came on the 12th of May this year, and on the 15th of May last year. The middle date of first frost is May 13th.
There were three rain days (usually four) but nearly all the rain (61 mm) was recorded on the 4th.

Weather log May 2019

Comparing May months

The mean temperature this month (14.6°) was high, but not as high as in May 2007 (15.1°). However, the mean daily minimum temperature (8.1°) was the warmest for May in the new century: above normal by 2.3°.
A rather narrow daily temperature range (13.1°) and high percentage of cloudy days (45%) showed moisture above normal.
The (estimated) rainfall total of 61.8 mm was very high, in the 75th percentile. Because no rain at all had fallen in April, the total for the two months together reached only to the 26th percentile.

Climate for May 2019

Drought

The on-going unprecedented drought is reported in another post.


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 2018, 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.

May 2019 rain gives some relief

Rainfall status Apr-May 2019

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 May, are shown by a thick black line with large circles. Those from one month earlier are shown by a thinner line with smaller circles. [The method is described in “Further Explanation” below.]

Changes from April to May

Above-average rainfall in May relieved the drought situation in some ways. Rainfall shortages of 3-, 4-, 5-, and 6-month duration are no longer serious. The 9-month shortage is reduced from severe to serious, and the 12-month shortage from extreme to severe.

May rain did not prevent the rainfall total for 15 months falling to the record low value of 388 mm. The record, which had been set at 404 mm in 1912, has been broken three times in this drought: to 400 mm in September, 397 mm in April, and 388 mm in May.

Nearly all rainfall shortages at long and very long durations have been reduced to some extent. However, extreme shortages persist not only at 15-months, but also at 18-, 24-, 30-, 72- 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

3-year trends to May 2019

May days not warm

3-year trends to May 2019

May raw anomaly data (orange)

In May 2019, the anomaly of daily maximum temperature returned to zero after years of positive values. Both daily minimum temperature and subsoil temperature anomalies were very high. Moisture anomalies, reflecting the high rainfall value (+21 mm), were low on the graphs (away from drought), but dew point was not as far down as “normal”.

 Fully smoothed data (red)

Fully-smoothed data now include the spring season ending November 2018.
Both daily maximum and daily minimum temperature anomalies were very high and rising. The minimum was rising faster and broke the record of +1.65°. Subsoil temperature anomaly, due to a phase lag, was normal and still slowly falling.
Moisture indicators in this spring were inconsistent. Rainfall anomaly decreased slowly to a new (20th century) record of minus 29.7 mm. The dew point anomaly was also low, but rapidly increasing. Both the cloudiness and the daily temperature range were normal.


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.
Continue reading

No Rain Days in April 2019

Split Rock Reservoir 4-5-19

A warm spell in the third week was 4.2° above normal. There were 29 days over 25°, many more than usual. Anzac Day (25th) was sunny, calm and warm. It reached 28.2°, which was four degrees above average for that day, but not up to the 28.7° of Anzac Day 2002.
There were no rain days (usually four) and the dew point on the 28th reached a record low April value of minus 3.2°. There were no frosts.

Weather log for April 2019

Comparing April months

This month was warm (average 19.8°), but not as warm as April 2018, 2016 or 2005. The mean daily maximum of 27.8° was well below that of April 2005 (29.5°).
There was no rain, as in April 1912, 1925, 1942 and 1971. Dry air was shown by early morning readings of low dew point (5.8°) and very low relative humidity (67%). However, normal moisture was shown by 30% cloudy days and a daily temperature range of 15.9°.

The last seven April months

Drought

The on-going unprecedented drought is reported in another post.


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 April 2019

April no rain

3-year trends to April 2019

April raw anomaly data (orange)

In April 2019, a rainfall total of zero made the raw anomaly for rainfall minus 40 mm. Rainfall, and the other moisture indicators (cloudiness, dew point, and daily temperature range) were much further up the graphs towards drought than they had been in March.
Daily maximum, minimum and subsoil temperatures were high, near the high-side limits of (smoothed) normal temperature.

 Fully smoothed data (red)

Fully smoothed data to October 2018 show rainfall just short of the record negative anomaly set in May 2018, and both maximum and minimum temperatures near record positive anomalies. However, cloudiness, dew point, and daily temperature range continued a movement (down) away from drought.


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.
Continue reading

April 2019: 7 lowest rainfall totals

In April 2019, rainfall totals were the lowest-ever values for 1 month and for 15, 18, 24, 30, 72, and 84 months.

Rainfall status Mar-Apr 2019

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 April, are shown by a thick black line with large circles. Those from one month earlier are shown by a thinner line with smaller circles. [The method is described in “Further Explanation” below.]

Record and near-record low rainfall totals

There never has been a month at Manilla when rainfall totals have included so many record or near-record low values.

  • The 1-month total for April is zero (as in April 1912, 1925, 1942, and 1971).
  • The 12-month total of 283 mm is second-lowest after February 2019 (271 mm).
  • The 15-month total of 397 mm is a new record, beating September 2018 (400 mm).
  • The 18-month total of 510 mm is a new record, beating April 1966 (514 mm).
  • The 24-month total of 745 mm is a new record, beating July 1966 (766 mm).
  • The 30-month total of 1005 mm is a new record, beating March 2019 (1078 mm).
  • The 72-month total of 3060 mm is equal-lowest with February 1903.
  • The 84-month total of 3653 mm is a new record, beating February 2019 (3672 mm).

Other changes from March to April

When rainfall in April was 55 mm less than in March, the short-duration totals for 3, 4, 5, and 6 months became serious shortages again.
New severe rainfall shortages appeared at the very long durations of 144 months (12 years) and 240 months (20 years). Such shortages have not been seen in half a century: not since 1969 in the case of 144 months duration, and not since 1950 in the case of 240 months duration.

May 2019 data

Data for the following month, May 2019, is plotted in the same way in the post “May 2019 rain gives some relief“.


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 March 2019

March warm

3-year trends to March 2019

March raw anomaly data (orange)

In March 2019, the raw anomaly for daily maximum temperature was near the upper limit for normal. Daily minimum and subsoil temperatures were high. Rainfall and other moisture measures were near normal.

 Fully smoothed data (red)

Fully smoothed data to September 2018 (except daily minimum temperature anomaly) showed a movement away from drought. More recent data, only partially smoothed, suggest that temperatures and rainfall later returned towards drought.


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.
Continue reading