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

Very warm nights in March 2019

Photo of dead public lawn

Our Nature Strip

While there were no very high or low temperatures, weekly mean temperatures were high. Warm spells through the second and fourth week-ends were about four degrees high.
There were nine rain days (twice the usual number for March), but none had more than 5 mm until the 30th. A rain front early that morning brought 39 mm.

Weather log for March 2019

Comparing March months

This month was very warm. It was like March in 2018 and 2016, but the nights were warmer. Both the mean minimum temperature (17.9°) and the monthly mean temperature (24.9°) were record high values for March in the 21st century.
It was not a dry month: values of all the moisture indicators were near normal. The (estimated) rainfall of 54.9 mm is very close to the long-term average of 53.4 mm. However, March rainfall at Manilla is strongly skewed, having many values just below the average and just a few values up to 240 mm above it. The median March rainfall is much lower: only 39 mm. This month’s total of 54.9 mm is at the 60th percentile: it is higher than 60% of all historic March rainfall values.

The last 7 March months

Drought

The on-going drought is reported in three posts, with three different kinds of graph:

  • a line graph shows rainfall status in the last two months, with duration on the x-axis and severity on the y-axis;
  • a contour graph shows 25 months sequentially on the x-axis, duration on the y-axis and severity by tints;
  • a duration graph shows how shortages began and ended in the last 20 years, with time on the x-axis and duration on the y-axis.

 


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 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

2018-19 summer 2nd driest

Cumulonimbus and towering cumulus

Storm at Dusk

This summer had 7 very hot days above 40°, and 11 very hot nights above 24°.
The worst heat waves came in January. Around the 17th, weekly temperatures were more than 6° above normal, with days at about 41°, and nights 24°. Near the 28th, nights were even warmer. Episodes of very low dew point came at times of lower temperature.
Thirteen rain days were scattered through the season, the highest readings being 25.0 mm on 16 December and 18.0 mm on 21 January.

Weather log summer 2018-19

Comparing summer seasons

Average temperatures were almost the same as in the hot summer of 2016-17. Days, at 35.5°, were slightly cooler and nights, at 20.1°, slightly warmer. The resulting average, 27.8°, was a new record summer temperature, beating 2016-17 by 0.2°.
Remarkably, the mean subsoil temperature, 25.5°, was not high, but normal.
Similarly, daily temperature range (15.4°) and cloudiness (22%) were normal. (Recent summers have been cloudy.) Dryness was shown only by very low humidity and rainfall.
The mean early morning dew point for this summer (10.4°) was second lowest in the 19-year record. Only that of summer 2013-14 (8.6°) was lower.
The total rainfall for the summer, 70 mm, was equal second driest with 1965, the driest summer being 1930, which had 66 mm.

Climate for summer 2018-19


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 this summer. I used my own readings for the whole season.

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

Warm, Dry February 2019

Photo of bushfire smoke at 40 km.

Bushfire at Warrabah

The month began warm, with weekly temperature three degrees above normal, but it ended slightly cool. Day and night temperatures remained near normal. The highest maximum was just under 40°.
The morning of the 13th had very dry air, with a dew point of only 1.7°. (Serious bushfires were burning that day.)
There were only 2 rain days (usually 7). Neither recorded as much as 7 mm.

Graphical log for Feb 2019

Comparing February months

After the extreme heat of January, February was only 1° warmer than normal, by day and by night.
Two indicators of moisture, cloudiness and daily temperature range, were normal. However, the mean early morning dew point, 9.2°, showed the lowest February humidity this century.
The monthly rainfall of 10.6 mm was at the 9th percentile, far below the average (67 mm). This was the 12th driest February, but it had more rain than either February 2017 (6th driest) or February 2015 (ninth driest).
I have reported the on-going drought in another post.

The last 7 February 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 February 2019

February arid

3-year trends to February 2019

February raw anomaly data (orange)

By February 2019, temperatures had returned from very high to normal. Rainfall remained very low, and dew point also became very low.

 Fully smoothed data (red)

Fully smoothed data to August 2018 showed that several trends for the spring were typical of drought:

Maximum temperature anomaly was steadily falling from the record high in March.
Minimum temperature anomaly was a little high and steady.
Subsoil temperature anomaly was falling towards normal from a low peak in June.
Rainfall anomaly was near the record low (smoothed) and steady.
Cloudiness anomaly was near zero.
Dew point anomaly was near the record low (smoothed) and steady.
Temperature range anomaly peaked rather high in July, then fell.

More recent data, only partially smoothed, suggest that temperatures and rainfall have since 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.

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.