August 2020: still gripped by extreme drought

Rainfall status Manilla drought to August 2020

Little rain fell in twelve months

In the past 12 months, only February (165 mm) and March (53 mm) had adequate rain at Manilla. Rain was so scarce that the 12-month total was just under 500 mm, far below the average of 652 mm. So the drought situation has not improved lately.

Seasonal to annual shortages were not serious

Through the year, most rainfall totals for 12-months or less have been below the average, but not serious shortages. The acute phase of the drought was over by February, if not much earlier.

Two-year to eight-year shortages were extreme

This worst-ever drought for Manilla has been marked by extreme (often record-breaking) rainfall shortages with durations from two years to eight years. They persist in the data for August 2020 shown in this graph.

Twenty-year and thirty-year shortages

The shortages with the longest duration included here had been near the 70th percentile in 2012, but are now very much worse. The twenty-year (240-month) shortage is now in the 1st percentile.

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 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

July 2020: extreme drought lingers

Rain status at Manilla NSW June and July 2020

The lingering long-term drought

As shown, Manilla is still in extreme drought: the rainfall totals from 30-months to 96-months are in the lowest 1% in history. Not only that, but the 42-month total to July (1440 mm) and the 96-month total (4056 mm) are the lowest ever recorded.

Acute drought in 2018 and 2019

This worst-ever drought at Manilla had a false start in September 2017, with severe 2-month and 3-month shortages (below the 5th percentile), but began in earnest in winter (JJA) 2018, with many extreme shortages (below the 1st percentile) that were shorter than one year duration. Such seasonal extreme shortages came again in spring (SON) 2019.
These acute shortages were ended by the rain of February 2020, but extreme and record-breaking shortages with duration of two or more years have persisted up to now.

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 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

June 2020: return to a 42-month drought record

Rain status at June 2020 at Manilla NSW

Changing shortages

Rainfall of 20.8 mm in June 2020 was far below the average (44 mm), reaching only to the 28th percentile.
Although this low rainfall did not cause any rainfall total for 12-months or less to become a serious shortage, all totals for longer durations were serious shortages or worse. Two were serious (<10th %-ile), six were severe (<5th %-ile), and nine were extreme (<1st %-ile). Nearly all of them had become drier than in May.
The 42-month total, which had set a driest record of 1468 mm in April, now beat this with 1457 mm in June. At two other durations, rainfall totals were 2nd-driest: at 84-months, 3471 mm; and at 96-months, 4142 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 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

A cool moist autumn in 2020

The daily weather log

[Note.
Due to illness, 45 days of this season, from 23rd March to 7th May, were missed for some Manilla values. No values were noted for cloud or soil temperature; mean values shown for the season are estimates only. Missed values of daily maximum and minimum air temperatures were estimated by regression on values from Tamworth Airport Automatic Weather Service.]

Instead of warm spells as in autumn 2019, this season had several cool spells. Three or four had cool days, but one in mid-march had cooler nights. Cool days in late May came with a very narrow daily temperature range, high humidity and cloud.
There were 18 rain days (normally 14) spread through the season, with the highest reading (20.0 mm) on the 1st of May.

Weather log autumn 2020

Comparing autumn seasons

In contrast to the previous two autumn seasons, autumn 2020 was cool and moist. Days (24.4 deg) were 2nd coolest for autumn in the new century (after 2003). Night temperatures were normal, and the mean one degree low.
The rainfall total, 124 mm, was at the 55th percentile, not far below the mean of 134 mm. Other moisture measures were higher: early morning dew point was 9.0 deg, cloudiness 41%, and daily temperature range 13.8 deg.

Climate for autumn 2020


Data. The Bureau of Meteorology automatic rain gauge, Manilla Museum, Station 55312, recorded no readings from 24th February 2020 until 11th March 2020. I used my own readings for that period. Readings later in autumn are from the Manilla (Museum) 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.

May 2020: as in March, no new drought records

Rainfall shortages at Manilla NSW

Changing shortages

Nine extreme rainfall shortages persisted at Manilla in May, one fewer than in April. No serious shortages occurred at 9-months or less. However, the 12-month total (440 mm) once again became a serious shortage (9th percentile).
The two rainfall totals nearest to record values for dryness were those that made new records most recently. The 42-month total of 1485 mm (2nd driest) had reached the record value of 1468 mm in April, while the 96-month total of 4141 mm (4th driest) had reached the record value of 4104 mm in February.

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 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