Weather experts should check rainfall figures before being quoted by the media

We have all seen articles such as this from The Australian, “Southeast Queensland storms in line with climate change: weather experts”. The article is referring to storms of 18-20 November and the journalist seems intent on getting his headline despite one of the experts cautioning against reading too much into the storms by saying, “..that a series of events by themselves did not “prove” climate change one way or the other.”

The real interest for me is not the ridiculous headline but the two experts quoted state that “..November in southeast Queensland had generally been a dry month over the past decade..”.
These experts are University of Southern Queensland professor of climate and water resources Roger Stone and Queensland weather bureau (BoM) spokesman Gavin Holcombe.
Now what are the facts about November rainfall in southeast Queensland over the past decade ? Lets look at November rainfall for central Brisbane and Gatton, home to the Professor’s University, taking November data for the 10 years 1998-2007 and comparing to long term averages for November.

We find that for Brisbane and Gatton, the November average 1998-2007 is either very close to or exceeds the long term BoM mean(average). So we see that experts much quoted by the media are not fully in touch with simple realities of rainfall statistics, facts they could check in minutes. Is this more evidence of a national delusion about rainfall in Australia ?

The long term rainfall record for Brisbane is “Brisbane Regional Office” which commenced in 1840 and closed in 1994, the November mean is 97mm.
Using this helpful BoM webpage to discover data near the centre of Brisbane I have made the following table from 7 Brisbane stations up to 6.2km from the centre of town, leaving out a few of the most gap ridden stations.
November Brisbane rainfall
BRISBANE REGIONAL OFFICE Site number: 40214 Commenced: 1840 Closed 01 Jul 1994
Mean for November = 97
7 stations up to 6.2 km from 27.47 degrees South – 153.03 degrees East

  • BRISBANE (BCC) ALERT Site number: 40839 Commenced: 1990
  • BRISBANE Site number: 40913 Commenced: 1999
  • HILLTOP GARDENS Site number: 40911 Commenced: 1999
  • BRISBANE SHOW GROUNDS Site number: 40216 Commenced: 1889
  • BRISBANE RPA HOSPITAL Site number: 40767 Commenced: 1988
  • LONG POCKET CSIRO LAB Site number: 40450 Commenced: 1968
  • ALDERLEY Site number: 40224 Commenced: 1899
  • UNIVERSITY OF QUEENSLAND GATTON Site number: 40082 Commenced: 1897

Mean for November = 77.7

My table above gives a Brisbane average of 99.9mm for November 1998-2007, just above the long term mean of 97, that is leaving in the 61mm for station 40839 for 2004 which might be incomplete.

Gatton has a long term record almost free of gaps and has a November mean of 77.7mm. I have not had to look for any other data there and as my table shows Gatton has an average of 90.09mm for November 1998-2007, well above the long term mean of 77.7mm.

With respect to Brisbane data it is interesting that although Brisbane Regional Office closed in 1994 no overlapping station appears on the above BoM webpage to replace it. You might expect the BoM would have started a replacement central Brisbane station before closing BRISBANE REGIONAL OFFICE Site number: 40214.
Maybe there is data somewhere but just not available on the above BoM webpage I have accessed.

Full text of article from The Australian, our national newspaper.

“Southeast Queensland storms in line with climate change: weather experts”
By Andrew Fraser
The Australian
November 21, 2008 12:01pm

ONE of Australia’s leading climatologists has warned the extreme weather that hit southeast Queensland this week is consistent with climate change modelling of weather patterns.

Southeast Queensland was hit with a heavy storm on Sunday night and again in the early hours of yesterday morning, with another predicted for last night and another tomorrow.

University of Southern Queensland professor of climate and water resources Roger Stone and Queensland weather bureau spokesman Gavin Holcombe said that while November in southeast Queensland had generally been a dry month over the past decade, big storms such as the last two were not unusual.

“They generally are a one-in-20-years event, but that doesn’t mean that you won’t get two or even more in the one week,” said Professor Stone.

“But this sort of violent weather activity is consistent with climate change predictions. We’re coming off a long drought in southeast Queensland, and that has been an extreme weather event. Now we’re getting these storms, and they’re also extreme weather events.”

He cautioned against reading too much into the storms, saying that a series of events by themselves did not “prove” climate change one way or the other.

Weather bureau records show that Brisbane generally has 11 rainy days during the month of November, but Mr Holcombe said that during the past decade rainfall in the month had been well under previous averages.

“But back in the 70s and 80s we did have plenty of Novembers which were very wet indeed. I just think people are now thinking of the sort of dry Novembers that we’ve had over the past decade as the norm, but if you look over the long term, there have been plenty of wet Novembers,” Mr Holcombe said.

He said there could be a bigger storm tomorrow. “The sort of warm winds over southeast Queensland combined with an upper trough moving over southeast Australia are the sort of conditions that allow a lot of storms,” he said.

END

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2 comments to Weather experts should check rainfall figures before being quoted by the media

  • Luke

    Brisbane Shizbane

    THE issue for Brisbanites in lack of rainfall in the region’s water storages – i.e. the Brisbane Valley behind the Diagular Range – sites like Esk, Kilcoy, Toogoolawah

    And SE of Brisbane – dams like Maroon Dam and Moogerah Dam have been critically low.

    Brisbane City itself hasn’t been too bad – but also check Ipswich 50kms to the SW too.

    The experience has been one of rains missing the dam catchments while leaving a green coastal tinge.

    The simulated inflow analysis of Wivenhoe Dam (based on a very well calibrated model of current conditions) showed that the Millennium Drought sequence exceeded the Federation Drought in terms of inflow. (no Wivenhoe Dam in 1902 obviously!).

    Many theories have been invoked – including and unconvincing tilt at air shed pollution. However this year possibly with the PDO switch and La Nina-ish lingering conditions all has changed. However Wivenhoe for all the rainfall is still only 31% capacity but Somerset now 91%.
    oldsite.seqwater.com.au/content/standard.asp?name=DamOperationsandMaintenance

  • WSH

    Thanks for the insights on Brisbane catchments Luke. Of course everybody would like to see more rain in dam catchments. Did you see my earlier articles on Brisbane catchment rain ?
    Brisbane catchments rainfall history 1900-2005
    August 20th, 2006

    By the way, the Maroon and Moogerah Dams are not SE of Brisbane, more like SW.
    I am sure I will write more on the region as time permits but just quickly back to the subject of the post. Despite two faxes the BoM and “The Australian” have not yet replied to my communications of a week ago.