Unprecedented South Australian Weather!

(and it has been like that for 178 years!)

There were more blackouts in South Australia a couple of days ago following a wild storm.  In a report in the Adelaide Advertiser, SA Power Networks spokesperson Paul Roberts is quoted:

“This is just another example of the unprecedented weather in the last six months,” Mr Roberts said, referring to bouts of wild weather that have hit power supplies hard this summer and the preceding spring.

21mm of rain was measured at the Kent Town gauge.

Just how “unprecedented” is Adelaide’s weather over the past few months?  I couldn’t find any records for the number of severe storms, so for a proxy I have made do with rainfall data from West Terrace and Kent Town in Adelaide.  The overlap period has very similar rainfall recordings so I joined the two series to give a record starting on 1 January 1839.  That’s 178 years of data.

When thinking about “unprecedented”, we need to check amount, intensity, and frequency.

Firstly, a few plots to give some context.  How unprecedented was Thursday’s storm?

Fig. 1: Rainfall for the first 21 days of January compared with Days 1 – 21 of every year

adelaide-rain-21-jan

Note Thursday’s rainfall had less rain than four previous occasions on this day alone, and 20 or so in previous Januarys.

Fig. 2: Rainfall for each day of 2016 compared with each day of every year:

adelaide-rain-2016

Note the December storm had extreme rain (for Adelaide) but not a record.

Amount and intensity has been higher in many previous years.  141.5mm was recorded on 7 February 1925.

Fig. 3: 7 day average rainfall over the years:

adelaide-rain-2016-7d-avg

The topmost dot shows the maximum 7 day average for each year.  2016 got to 13.4mm on 4 October- multiply by 7 to get the weekly total rain.  Note there were many wet and dry periods all through the record.

21mm of rain fell in a severe storm on Thursday, so I arbitrarily chose 20mm as my criterion for heavy rainfall in one day as a probable indicator of stormy weather.  I am the first to admit that 20mm might fall steadily all day and not be at all associated with wild winds, and wild winds can occur without any rain, but bear with me.

Fig. 4: Rain over 20mm throughout the year:

adelaide-rain-2016-above-20

There seems to be no increase in amount or intensity of rain at any time of the year.

Fig. 5: Frequency:

adelaide-rain-2016-cnt-above-20

Note 2016 had 7 days with above 20mm in 24 hours.  That’s the most since… 2000, when there were 8 days- and many previous years had 7 or 8 days, and 1889 had 9.  So no increase in frequency.

However, Mr Roberts was referring to the last six months, spring and summer.  So let’s look at rain events over 20mm from July to December, firstly amounts recorded:

Fig. 6: July to December Rain over 20mm:

adelaide-rain-above-20-last-6m

Nothing unusual about 2016.

Fig. 7:  Frequency of heavy rain July – December:

adelaide-rain-2016-cnt-above-20-last-6m

1973, 1978, and 1992 had the same or more days with over 20mm.

I now restrict the count to spring and summer only:

Fig. 8:  Spring and Summer frequency:

adelaide-rain-2016-cnt-above-20-last-4m

Not unprecedented: 1992 had one more.  Add in last Thursday’s event to make them equal.

Conclusion

Adelaide has a long climate record, showing daily rainfall has varied greatly over the years.  There is no recent increase in amount, intensity, or frequency for the whole year, or for the last six months or four months.  Spring and summer rainfall in 2016 was not unprecedented, and to the extent that spring and summer falls over 20mm are a proxy for storms, there is no evidence for an increase in wild weather.  This is normal.  Get used to it, Mr Roberts, and make sure the electricity network can cope.

 

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12 Responses to “Unprecedented South Australian Weather!”

  1. Ian Hill Says:

    It is only unprecedented since they blew up the Port Augusta coal powered station last year. From Saturday’s Advertiser: “The latest downpour on Thursday, described by Bureau of Meteorology climatologist Darren Ray as a ‘one-in-five-years’ event, doubled January’s total rainfall.”

    The Kent Town (and formerly West Tce) sites are not a good indicators of the REAL amount of rain which falls in the Adelaide Metropolitan Area. Most suburbs to the north, east and south get much more.

    I was waiting for Thursday’s storm with anticipation but it was a few hours late and a fizzer where I live (in the southern suburbs), although the temperature dropped about 10 degrees in three minutes. Interesting cloud formations though.

    Storms like Thursdays occur a few times a year in Adelaide. I distinctly remember in the late 1970s when we had tropical weather for a whole month – it was a March – and the power managed to stay on all the time.

    Mr Ray expects there to be another storm in SA around the end of January/early February.

    • kenskingdom Says:

      What do you think of my 20mm of rain proxy for storms? Is that a reasonable assumption?

      • Ian Hill Says:

        Certainly a good starting point Ken. As you note, it can rain without wild winds and vice versa. Storms here invariably move on quickly, so with instances of consecutive days of 20+ mm, the second and subsequent days could be eliminated. But if you are going to look at that, you could drop it to 15 or 10mm.

        You could also incorporate temperature – 20mm of rain on a cool day in summer (say <25C) is unlikely to be a storm – but I think it's better to keep it simple.

        • kenskingdom Says:

          Thanks. I redid the count deleting consecutive days of >20mm. It made no difference to July to December/ September to December counts, but did affect counts for the whole year e.g. autumn and winter rain. So 20mm still holds! Will look at 10 or 15 tomorrow.

    • John in Oz Says:

      “The Kent Town (and formerly West Tce) sites are not a good indicators of the REAL amount of rain…”

      Nor of temperature.

  2. kenskingdom Says:

    Gday Ian
    Using 10mm or 15mm and deleting any second days as you suggest for September to December changes the count of days obviously but not the shape of the plot- 2016 is still behind 1992 and some other years.

  3. Ian Hill Says:

    Thanks Ken. I expected that to be the case.

  4. ngard2016 Says:

    Ken this is not about this topic. But do you have a trend map link like this one from RSS that shows the world since 1998? I’m particularly interested to show OZ cooling since that time. There are many doubters out there. I can’t seem to find anything at Roy Spencer’s that covers that period for UAH V 6.

  5. ngard2016 Says:

    Sorry here’s the link.
    http://images.remss.com/msu/msu_data_monthly.html?type=trend&channel=2

  6. ngard2016 Says:

    Ken can you please send me an email? I want to show you something about UAH V 6 and your pause updates. I’m sure you would want to look at this. Thanks.

  7. ngard2016 Says:

    Ken, I posted this at Don Aitkin’s blog and wonder if you’d care to comment?

    There have been some strange things going on with the word’s temp data-sets since Phil Jones’s 2010 interview with the BBC. The warming trend from 1910 to 1940 was 0.150 c/ decade, but that has now changed to 0.129 c/ decade first HAD 4 column and 0.139 HAD 4 Krig data.

    But here is the interesting part, GISS data shows just 0.090c/ decade and the Berkeley data is 0.143 c/ decade, plus NOAA is just 0.090 c /decade. But even NOAA land trend is now below what Jones quoted for L&O in 2010. In fact NOAA Land trend is just 0.134 c / decade today. This has be nonsense when even the much faster land trend can’t reach Jones’s L&O trend in 2010. Yet Berkeley land trend is 0.172 c/ decade for that period.

    But move forward and look at the trend from 1910 to 1945 ( 36 years) and we find more strange results. Had 4 trend is 0.140 c/dec, Had 4 krig is 0.151/ dec, NOAA is 0.134c /dec, GISS is 0.133 c/ dec and Berkeley jumps to 0.160 c/ dec.

    NOAA land trend is now 0.145 c/ dec , while Berkeley land trend is now 0.173 c/ dec. Clearly there have been adjustments made for HAD data since 2010 and the GISS and NOAA temp trends are ridiculously low for the period 1910 to 1940. But they do help to raise the later overall trend I suppose. Please note that Jones chose the trend period 1910 to 1940 and they are not a cherry pick.

    Here’s the York uni tool.

    http://www.ysbl.york.ac.uk/~cowtan/applets/trend/trend.html

    And here’s Jones’s 2010 BBC interview.

    http://news.bbc.co.uk/2/hi/science/nature/8511670.stm

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