Australian Government understating Perth catchment rain
Following above average rain in May-June-July over Perth dam catchments I was puzzled that I had seen an Australian Govt Bureau of Meteorology (BoM) rep speaking on TV late in July saying that while July rain was good May had been dry and June very dry. 
 However I did email the BoM  and their reply included URL's to the following three "drought" maps for May, June and July. Emails are copied below.

Small extracts from  BoM maps made at  http://www.bom.gov.au/cgi-bin/climate/rainmaps.cgi
	Location only map showing Perth dam catchments approx position as row of x's. Ignore the colouring, location map only. Will help readers not familiar with Perth to eyeball  the catchment locations on the May to July maps When talking about rainfall amounts below we will refer to two measurements of what is average. One is the BoM average which must be the long term or all time rain average, often circa 100 years. Then I will also refer to the post 1975 average which is most relevant to Perth water supply issues  because SW WA rain shifted down ~10%  in the mid-1970's  to a new rain regime typified by an absence of high rain years and generally more consistent levels. See BoM graphic of long term SW WA rain 1900-2006; which demonstrates with crystal clarity that the high rain years from WWI  to ~mid 1960's  have ended. I say it is misleading in terms of Perth water supply issues to be referring to the all time rain averages, as the BoM and WA Govt does.  It is vital that for a more rational view of SW WA water resource issues, the post mid 1970's rain averages are used, as I do below.
	Since starting this page the BoM 3 month   map of rainfall deciles has come to hand. From the BoM rainfall  Outlook current page National Seasonal Rainfall Outlook: probabilities for Spring 2007 , issued 23rd August 2007 , Mixed odds for spring rainfall (While you are at the BoM page, note their prediction that Sept-Nov will be wetter than average in SW WA. ) This map to the left is stunningly at odds with ACTUAL  May-June-July   Mundaring, Karnet and Dwellingup (averaged)  rain which was 552 mm,  or 97.6% of the all time average of  565.6 mm. and 108.5% of the post 1975 average of  508.9 mm.
	The 3 maps below here are not essential to my case now I have the above May to July map,  but are left in
	Note the speck offshore from Perth is Rottnest Island. On this BoM  drought map for May 2007 the vast majority of Perth catchments are shown as, Below average - rainfalls in the lowest 30% of historical totals, but not in the lowest 10% Yet an average of Mundaring, Karnet and Dwellingup rain for May showed  134.4 mm which is 90.9% of the all time average of  147.8 mm. The 134.4 mm of actual rain for May  is 97.2% of the post 1975 May average of  138.2 mm
	June rain was poor and  an average of Mundaring, Karnet and Dwellingup rain  showed  118.4 mm which is 52.5% of the all time average of  225.3 mm. The 118.4 mm of actual rain for June  is  59.2% of the post 1975 June average of  199.9 mm
	July was somewhat wet and  an average of Mundaring, Karnet and Dwellingup rain  showed  309 mm which is 137.4% of the all time average of  224.8 mm. The 309 mm of actual rain for July  is 148.5% of the post 1975 July average of  208 mm

For the full May-June-July  period, Mundaring, Karnet and Dwellingup rain was 552 mm which is 97.6% of the all time average of  565.6 mm.
and 108.5% of the post 1975 average of  508.9 mm.  
My main point is  the fact that those stations got 108% of average post 1975  May-June-July rain, which should be good news in respect of Perth water  crisis issues, is NOT represented on these BoM maps.
On current media performance, it is unlikely Perth people will be told this good news about catchment rain, yet we constantly hear rain minimised in the media.
The years 2002-2003-2004-2005  had near average May-October rain in dam catchments, yet who has ever heard this ?
Our Premier says in Parliament  SW WA rainfall has stopped.
For years WA Govt water authorities  have conned the media with propaganda and spin about rainfall,  "our drying climate" ad nauseum.
Across an arc of southern Australia from Brisbane to Perth, water supply shortages are huge issues and solutions favoured by politicians are usually multi-$Billion, high enviro impact  seawater desalination plants.
Yet, amazingly we are not reporting  accurately and with clarity,  free rainfall that falls from the sky over our dam catchments in huge quantities.
The BoM forthwith should commence special rain reports on all metro dam catchments for our major cities.

Profligate Govt waste of water following average catchment rain
above page has many links

Explanation of map colours above.
On the BoM drought page at http://www.bom.gov.au/climate/glossary/drought.shtml
they say about the colour scheme on the above three maps,
Pale Blue=Above average - rainfalls in the highest 30% of historical totals, but not in the highest 10%
White = average = rainfalls in the middle 40% of historical totals
Pink =Below average - rainfalls in the lowest 30% of historical totals, but not in the lowest 10%
Med Red=Very much below average - rainfalls in the lowest 10% of historical totals
Read their page for full exposition.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Emails to and from the BoM.
From me to the BoM
I saw you on TV news around the end of July and you conveyed an impression that although there had been rain in July,  May and June rains had been poor.
In fact for Perth dam catchments, taking the longer term BoM stations, Mundaring, Karnet and Dwellingup as a guide to that region, May, June, July rain has been just over average, despite a poor June.
So I think you conveyed a poor impression of reality to the TV audience.
But perhaps you were discussing regions other than Perth.
You went on to say that August rains would be poor.
In fact the first 10 days of August has been over average for the above three stations.
So was your crystal ball into August looking past the first 10 days ?
Did you really mean to say, "The first third of August will be normally wet but then August will be very dry" ?
I think that when you or other BoM people speak about rainfall in the media xxxxx, Australian taxpayers would expect you to be quite accurate about rain that has fallen and been measured. I do not think you were in this case.
I would also say that if the amount of rain in the first 10 days of August has  surprised you, you should go on the media and give us your current view.
Always looking forward to what the BoM has to say,
Warwick Hughes.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
BoM reply
Thanks for your query.

Please see below for embedded responses to your questions/criticisms.

For more comprehensive answers to your questions below, I would need to
obtain a copy of the original interview from the TV station involved.

I appreciate your comments and will look at our current methods of
climate monitoring and communication so that the best possible
information is provided via the media to the general public.

Regards

Original message
Subject: Perth water supply dam catchment rainfall

I saw you on TV news around the end of July and you conveyed an
impression that although there had been rain in July, May and June
rains had been poor.
In fact for Perth dam catchments, taking the longer term BoM stations,
Mundaring, Karnet and Dwellingup as a guide to that region, May, June,
July rain has been just over average, despite a poor June.
So I think you conveyed a poor impression of reality to the TV audience.
But perhaps you were discussing regions other than Perth.


****************
If I recall the TV station and the basis of the interview correctly (you
don't mention the TV channel and I did a couple of interviews at that
time) I was speaking about SW WA in general and based my comments on the
May, June and July rainfall maps on the Bureau website:

ftp://ftp.bom.gov.au/anon/home/ncc/www/rainfall/decile/month/colour/hist
ory/wa/2007050120070531.gif

ftp://ftp.bom.gov.au/anon/home/ncc/www/rainfall/decile/month/colour/hist
ory/wa/2007060120070630.gif

ftp://ftp.bom.gov.au/anon/home/ncc/www/rainfall/decile/month/colour/hist
ory/wa/2007070120070731.gif

As you will see the maps are generally consistent with the comments you
say I made. Looking at the Mundaring, Karnet, Dwellingup and Perth
Metro rainfall for May, June and July, I've categorised the monthly
recorded rainfall using the scale in the rainfall maps (ie. comparing
the decile value for each month with the long-term deciles) below:

May June July
Mundaring Average Very Much Below Average Above Average
Karnet Average Below Average Very Much Above
Average
Dwellingup Below Average Very Much Below Average Above Average
Perth Metro Below Average Very Much Below Average Average

I can see that some of the Perth Catchment areas recorded an average May
and this could be seen as being inconsistent with my comment about poor
May rainfall, however my comments were based mainly on the May rainfall
analysis and the Perth Metro data. Your example above highlights how
difficult it is to summarise the rainfall recorded across a large area
in one or two sentences (as well as in relatively coarse level rainfall
analyses), and from memory I wasn't asked to comment on the Perth
catchment specifically.
*******************
You went on to say that August rains would be poor.
In fact the first 10 days of August has been over average for the above
three stations.
So was your crystal ball into August looking past the first 10 days
xxxx x ?
Did you really mean to say, "The first third of August will be normally
wet but then August will be very dry" ?
I think that when you or other BoM people speak about rainfall in the
media xxxxx, Australian taxpayers would expect you to be quite accurate
about rain that has fallen and been measured. I do not think you were in
this case.
I would also say that if the amount of rain in the first 10 days of
August has surprised you, you should go on the media and give us your
current view.
Always looking forward to what the BoM has to say,
Warwick Hughes.
***************
Without seeing the interview it is difficult for me to recall exactly
what I said about August rainfall, however I presume my comments about
early August were based on computer model forecasts. These currently
extend to approximately 8 days:

http://www.bom.gov.au/jsp/watl/rainfall/aggregate.jsp\?model=4day&date=1t
o4

I consider these model forecasts to be particularly useful, however they
are of course not perfect and so there will be occasions where they are
inaccurate and misleading. I apologise if this was the case on this
occasion, however I do not recall whether this was the case.

I'd be surprised if I made any particularly confident predictions beyond
early August, as this moves beyond the realm of relatively accurate
computer models, and so are based on current seasonal patterns and
statistical outlooks.

Unfortunately, many media opportunities are poorly suited to the
reporting of accurate data and comment as they are dictated by the
agenda of the media representatives at the time and who are often not
interested in comprehensive detailed information. We try our best
however, we are very much constrained by such media opportunities due to
their generally brief nature and broad focus.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

End for now