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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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”.

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.

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.

December 2017 as in 2016

Blooms of San Pedro Cactus at Manilla NSW

San Pedro Cactus 2017

The weather in this December was very like the weather a year ago. Even details were similar. Each had just one 40° day. Each had one night near 25°, about 9° above normal. This December had one hot spell 6.3° above normal: last December had two hot spells 4.8° and 3.6° above normal. Neither had cool spells.
This December’s highest rainfall reading, 15.5 mm (unofficial), was like last December’s 17.8 mm (also unofficial). This month had fewer rain days (5 vs. 12) and longer dry spells.

Weather log for December 2017

Comparing December months

This was one of the hottest Decembers in the new century. The mean daily maximum, at 33.7°, equals that of December 2005, but is beaten by 33.8° last December. The mean daily minimum, at 18.2°, equals that of last December, but is not as warm as the 18.6° of December 2009. By contrast, December 2011 was the coldest, with a mean maximum of only 27.0°, and a mean minimum of only 13.9°.
This month’s subsoil temperature (23.0°) was very cool; one of four December values more than a degree below normal.
Like last December, this month was not very moist, but not very sunny either.
The rainfall of 48.2 mm was practically the same as in December 2016 and 2013. It is at the 35th percentile: not high, but high enough to prevent shortages.

Climate in December months

The Year 2017 was warm and dry

In this record (2000 to 2017), Manilla’s average annual temperature this year (18.65°) shows it to be the third warmest, after 2014 (19.01°) and 2009 (18.85°). The coolest was 2008 (17.19°), which was also cool globally. (Apart from 2008, Manilla annual temperatures do not follow global temperatures closely: the hottest year globally (2016) was not a very warm year here.)
Like the previous two years, 2017 had night temperatures half a degree below the normal value. Day temperatures, which had been near normal in 2015 and 2016, became a degree warmer. This year’s subsoil temperature (19.80°) was cool, very much cooler than in 2013 (22.19°).

It was a year of very low rainfall: 517 mm, which is at the 20th percentile, and 135 mm below the average (652 mm). Three even lower rainfall totals have occurred in the last sixteen years: 366 mm in 2002 (2nd percentile), 495 mm in 2009 (16th percentile), and 447 mm in 2014 (8th percentile).
Manilla yearly rainfall history: four momentsThis unusually high ratio of very dry years agrees with other patterns seen in Manilla’s annual rainfall. That is, in the moments of the frequency distributions. Recently, Manilla’s annual rainfall has had (i) very high kurtosis, showing increased extremes (“fat tails”), and (ii) negative skewness, showing that these extremes are low extremes, not high extremes.


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.

November 2017 dry again with cold nights

Cockatoos feeding in a wattle

Corellas in Acacia decora

While day temperatures were normal, many nights were below normal, around 10°. The cold night air was extremely dry. The early morning dew point on the 1st was minus 3.6°, about 14° below normal.
My rain gauge registered seven rain days, but readings were moderate, the highest being 14.0 mm on the 30th. (The automatic gauge at the Museum remained down.)

Weather log for November 2017

Comparing November months

With a mean of 20.8°, this month was cool, but not as cool as several other November months. November 1999, at 19.4°, was the coolest. On the graph, November 2014 (25.4°) stands out as very much warmer.
The rainfall of 44.2 mm is at the 31st percentile: not high, but enough to prevent any shortages. This graph still includes November 2011, the wettest on record. At 242.9 mm, it beat a record of 226 mm that had stood for fifty years.

Climate log for November


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 last reported on 24 September 2017.

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

October 2017: no drought

Grevillea robusta flowers

Flowers of Silky Oak

No temperatures were extreme in this month. In the second week, the mean weekly temperature was four degrees above normal, rather like the last week of September.
Dry air on the 6th and on the 31st made the dew point eight degrees low, but humid air on the 11th made it seven degrees high.
My rain gauge registered six rain days, with high readings of 38.5 mm on the 9th, 22.0 mm on the 12th, and 16.8 mm on the 21st. (The automatic gauge at the Museum remained down.)

Weather log for October 2017

Comparing October months

As shown by the arrow on the second graph, October months became warmer and more moist with each year from 2012 to 2015. October 2016 was very cool, then this month was again warm. The trend to more moisture continued through all six October months from 2012 to 2017. It was shown not only by rainfall, but also by cloudiness, dew point, and narrowing daily temperature range. No other calendar months had this trend.
The high total rainfall of 84.1 mm (80th percentile) wiped out the serious and severe rainfall shortages seen in September. Now, the lowest percentile value is that for the 4-month total (117 mm). Being at the 15th percentile, it does not rate as serious.

Climate for October


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 last reported on 24 September 2017.

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