March 2018 very warm indeed

Acacia salicina

Young Cooba

Eight days went over 35° this March, beaten only by nine days in March 2016. The 19th (38.6°) was the fifth hottest March day of the new century. Weekly mean temperatures rose to 4.6° above normal by the 18th, and remained almost as high beyond the end of the month.
There were seven rain days, with the highest reading of 16.5 mm (est.) coming early in the month.

Weather log for March 2018

Comparing March months

Average temperatures this month very nearly match those of the record-breaking March 2016. They are only 0.1° lower! Moisture variables are also similar: rather dry, in stark contrast to the sogginess of March 2017.

The rainfall total of 25.6 mm (est.) was at the 40th percentile, well below the average (53 mm). Serious rainfall shortages are seen only in the medium term: the 60-month total of 2770 mm (8th percentile) and the 72-month total of 3410 mm (9th percentile).

Climate in March 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 gauge, which had last reported on 24 September 2017, came on line again on the 16th of March. However, not all later days have readings reported.

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

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3-year trends to March 2018

Hot and rather dry

3-year trends to March 2018.

March raw anomaly data (orange)

March 2018 was more like January than February. Day and night temperature anomalies were high. Moisture anomalies retreated somewhat from very low values. Subsoil temperature moved back from low to normal.

 Fully smoothed data (red)

In the latest fully-smoothed data, for September 2017, temperatures, which had been static, began to increase. On the other had, moisture anomalies, which had been moving up the graphs towards drought, became static.

Earlier, the month of February 2017 marked a sharp reversal of trend in climate anomalies. Daily maximum temperature anomaly peaked. Most anomalies (not rainfall) retraced in March and April the values of January and December. The curvature of the trace (relative to daily maximum temperature anomaly) kept the same sense after April 2107 as before December 2016. For subsoil temperature anomaly, the trend reversal came four months later, in June 2017.


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.

Annual Rainfall Extremes at Manilla NSW: V

V. Extremes marked by high kurtosis

Manilla annual rainfall kurtosis

This graph shows how the extreme values of annual rainfall at Manilla, NSW have varied, becoming rarer or more frequent with passing time.
The graph quantifies the occurrence of extreme values by the kurtosis of 21-year samples centred on successive years.

The main features of the pattern are:
* Two highly leptokurtic peaks, showing times with strong extremes in annual rainfall values. One is very early (1897) and one very late (1998).
* One broad mesokurtic peak, in 1938, showing a time with somewhat weaker extremes.
* Broad platykurtic troughs through the 1910’s, 1920’s, 1950’s, 1960’s and 1970’s, decades in which extremes were rare.
All these features were evident in the cruder attempts to recognise times of more and less occurrence of extremes in Parts I, II, III and IV of this series of posts. This graph is more precise, both in quantity and in timing.

However, kurtosis (the fourth moment of the distribution) does not distinguish extremes above normal from those below normal. It is known that some early dates at Manilla had extremes that were above normal, and some late dates had extremes that were below normal.

Use of skewness

Extremes above normal are distinguished from those below normal by the third moment of the distribution, that is, the skewness.
Manilla Annual rainfall history: SkewnessThe post “Moments of Manilla’s Yearly Rainfall History” shows graphs of the time sequence of each of the four moments, including the skewness (copied here) and the kurtosis ( the main graph, copied above). The skewness function, like the kurtosis function, relates to the most extreme values of the frequency distribution, but to a lesser extent (by the third power, not the fourth).

I have shown the combined effect of kurtosis and skewness on the occurrence of positive and negative extremes in this data set in the connected scatterplot below.

Manilla rain skew vs.kurt

The early and late times of strong extremes were times of strongly positive and strongly negative skewness respectively. As kurtosis fell rapidly from the initial peak (+0.9) in 1897 to slightly platykurtic (-0.4) in 1902, the skewness also fell rapidly, from +0.7 to +0.3.
Much later, in mirror image, values were almost the same in 1983 as in 1902, then kurtosis rapidly rose while skewness rapidly fell, until kurtosis reached +0.9 and skewness -0.3 by 1998.
Between 1902 and 1983, while kurtosis remained below -0.2, the pattern was complex. In the decades of strong platykurtosis (below -0.9) there were extremes of skewness: +0.7 in 1919 and -0.3 in 1968.
Note that the skewness range was as high in times of low kurtosis as in times of high kurtosis, and the same applies to kurtosis range in relation to skewness. Conversely, when either moment was near its mean, the range of the other was not high.


See also:
“Rainfall kurtosis matches HadCRUT4” and “Rainfall kurtosis vs. HadCRUT4 Scatterplots”.

Summer 2017-18 very warm

Many cockatoos in a tree

Noisy Cockatoos

The heat waves of this summer were several degrees cooler than those of last summer. Also, unlike last summer, there were several cool spells between them. Arid spells with extremely low dew points came in mid-January and mid-February.
While last summer had 12 very hot days (over 40°), this summer had only 4; not as many as in the summers of 2013-14 (5), 2003-04 (6) or 2002-03 (5).
For most of the season, as falls of rain were light, and came at increasingly long intervals, the soil became very dry. That changed on 25 February, which had rainfall of 54 mm.

Graphical weather log for summer 2017-18

While this summer is the second-hottest of the new century in Manilla, its mean temperature (26.6°) is a degree below last summer’s 27.6°, and close to that of 2005-06 (26.3°). The subsoil temperature has been low (24.6°) in each of the last three summers. Two other measures have held steady, but a little high: cloudiness at 38%, and daily temperature range at 16°.
While the mean dew point is lower (less humid) than in last summer, the total rainfall is higher. At 140 mm (estimated), the rainfall is still well below the summer mean of 227 mm. It is at the 20th percentile, perhaps the 25th driest summer from 1883.

Climate for summer 2017-18


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. That gauge failed (again) on the 25th of September 2017, and later readings are from my non-standard gauge.

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

February 2018 had heavy rain at last

Wave cloud photo

Lenticular over Warrabah

Although there were eleven hot days over 35° this month, no days went over 40°. On the average, the second week was just 3.4° above normal, but the first week had been 3.5° below. Through most of the month, the weather was sunny with little rain, making the soil extremely dry. A drought seemed likely.
A violent front on the 25th brought an estimated 54 mm of rain: the heaviest fall in years. There is no official record of this rain event. Nor is there an official record of the only recent events of such a large amount: 47.0 mm on 4 February 2016, and 54.5 mm on 17 June 2015. The latest official readings that were higher were more than five years ago. They were in the record-breaking month of November 2011: 60.8 mm on the 14th, and 62.9 mm on the 27th.

[See note below on “Very wet days at Manilla”.]

Weather log for February 2018

Comparing February months

Compared to last February, this one was not nearly so hot and not so dry. Nights were near normal and days, at 33.9°, only one degree above normal (32.9°). Despite other signs of high moisture, the early morning dew point of 9.9° was very low.
Thanks to the one day of heavy rain, the estimated monthly rainfall total (71 mm) was above the average (67 mm) and at the 65th percentile. Among totals for more than one month, there is just one serious shortage. The 72-month (6-yr) total of 3400 mm is at the 8th percentile (450 mm low).

Climate in February months

Note.
Very wet days at Manilla

Log of decade totals of rainfall excess, Manilla, NSWDaily rainfall amounts of over 50 mm (“flooding rains”) are extreme events that feature in several posts on this blog. A graph in the first post on the topic is a log of every very wet day in the 130-year record. In a second post, I graph the pattern of how the total rainfall in very wet days changes decade by decade (Graph copied here.). Very wet days have a curious relation to drought that is analysed in “More Droughts After Heavier Rains”, Parts I, II, and III.


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, but it is not.  The gauge last reported on 24 September 2017.

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

3-year trends to February 2018

Warm

3-year trends to February 2018

February raw anomaly data (orange)

February 2018, unlike January, had days that were not very hot and nights with normal temperature. Rainfall rose to a normal value. Continuing low moisture was shown only by a very low dew point and a wide daily temperature range.

 Fully smoothed data (red)

Data for winter (JJA) 2017

These latest of the fully-smoothed data points showed that last winter was near-normal and changing little in most respects. Both dew point and temperature range were moving up their graphs towards aridity. Daily minimum temperature and subsoil temperature were cooling.

Main patterns of fully-smoothed data

In this period, the only major departure from normal climate was the cool moist winter (JJA) of 2016. Loops in the top four graphs show that more moisture preceded lower temperature. Minima in daily minimum temperature and in subsoil temperature came several months later, at the end of spring.


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.

January 2018 hot and dry

Brushtail possum resting

Brushtail Possum

The first heat wave of the month was nearly five degrees above normal: a little worse than last January’s. Rain, mainly on the 12th, brought a cool spell with very dry air. A second heat wave was not so bad, and it was gone by the 31st.
Three days went over 40° (but January 2003 had five) and three nights did not go below 25° (a January record).
Rain fell on five days (usually seven), the highest reading being 15 mm.

Weather log for January 2018

Comparing January months

The average temperature this January (27.9°) was not as high as last January (28.7°), or even January 2013 (28.2°). The days (36.2°) were second hottest after 2017 (36.4°), but the nights (19.7°) were only fourth hottest.
The estimated rainfall of 20.6 mm was low: at the 11th percentile, and only one quarter of the January average (87 mm). However, there are still no serious rainfall shortages. The lowest percentile value (12th percentile) is the five-year total of 2760 mm, which is 440 mm below the normal five-year total of 3200 mm.

Climate in January 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, but it is not.  The gauge last reported on 24 September 2017.

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