BOM rainfall measurements for Mitcham

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BOM rainfall measurements for Mitcham

Post  Luken on Sun Sep 06, 2009 5:55 pm

So I got the link to the BOM rainfall site from Karl (thanks again). This one is Mitcham, not far from where I live.

http://www.bom.gov.au/jsp/ncc/cdio/weatherData/av?p_nccObsCode=136&p_display_type=dailyDataFile&p_startYear=2009&p_stn_num=086074

Love having the details of past rainfall and a fantastic resource. Except!

It has missed lots of days rainfall over the last couple of weeks and has totalled the August falls, but missing multiple days.

However the years past seem to be complete. Has there been a problem last month? Or will they just catch up and enter the proper amounts at a later time?

Most noticably a 10-12mm fall in the last week of August, and I was about to say the 8.5mm I recorded here on Friday, except that seems to have been entered but at 20.4mm for the 5th....WTF? It might have been the 24 hours to 9am on the 5th, but sure as hell we didn't get 20.4mm Friday into Saturday.....


I am very confused....


So anyone know anything about these automatic (I assume) readings and their accuracy?
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Re: BOM rainfall measurements for Mitcham

Post  Luken on Tue Sep 08, 2009 5:57 pm

So what no one has any idea what goes on with these readings?

Are they automatic?

Does anyone check them?

What happens to the missed days rainfall?

Any info appreciated. flower
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Re: BOM rainfall measurements for Mitcham

Post  Karl Lijnders on Tue Sep 08, 2009 8:32 pm

Hey mate.

I think with the rainfall gradients in events like these, you have to use the AWS and rainfall readings as a guide and really take note of your own recordings. You can find variances in mm readings in distances less than a km. People think I have a hose dripping into my gauge, and over the years I have copped some very funny emails about it and some abusive (didn't know it was so competitive) but even tonight I have noticed that Scoresby has 7mm but I have 11mm down the road ~4km to N. Just that slight angle to the NE in the showers sent the showers streaming through from here to where Michelle is in Boronia where she has nearly 11mm, but up the hill from Boronia to The Basin (~3-4km) there would be a gradient of 1-2mm per km and further to DJ in FC.

As for info going missing I am not so sure, maybe DJ can help?
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Re: BOM rainfall measurements for Mitcham

Post  Luken on Wed Sep 09, 2009 5:38 pm

Yeah but im talking at least double the amount recorded in less than a KM, which I can't believe to be true. And just now on ABC news the weather reader said Mitcham got 30mm overnight! ......WTF........ I tipped out 17mm and that was from Monday morning. And the sort of rain we had which was showers, tending to torrential drizzle certainly wouldn't vary that much in such a short distance.

Now my rain guage is a plastic cup with numbers down the side, but are they really that inaccurate?

And I just checked....sure enough Mitcham recorded 30mm overnight accoeding to the BOM link!!! So very confused.

But thanks for the reply Karl.
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Re: BOM rainfall measurements for Mitcham

Post  hillybilly on Wed Sep 09, 2009 5:52 pm

Mitcham obs are from Melbourne water. Quite a lot of data seems to go missing in real time. Is worth checking the Melbourne Water site at http://melbournewater.com.au/content/rivers_and_creeks/rainfall_and_river_level_data/site.asp?SiteID=163 which seems to be more reliable on a day by day basis.

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Re: BOM rainfall measurements for Mitcham

Post  Karl Lijnders on Wed Sep 09, 2009 6:26 pm

Yeah 17-20mm may be the limit on rainfall out there in Mitcham with the higher falls reserved for the Mt Dandenong region from about Bayswater North eastwards along Canterbury Rd.

Anyhow the link DJ has provided is really the answer I WAS trying to get at today but I have had my brain melt a little bit today - AFL finals do it to me Razz
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Re: BOM rainfall measurements for Mitcham

Post  Luken on Thu Sep 10, 2009 7:26 am

O.K what is confusing me, is that suddenly my totals and the official totals are way out of sync.

The offical totals are almost double what I have been reading over the last few weeks.

Maybe my rain gauge has a small leak in it??

But wouldn't 21mm last friday (my reading 8.5), then 7.5mm on Monday (my reading 3.5mm) followed by 31.6mm (my reading 17.5mm), seems strange.

That would mean the figures that are being officially recorded are about the same or higher than what Karl and David have got for the same events.

Sorry guys can't remeber your figures exactly, but would have to be close.

And the pattern of Monday/Wednesday this week was that the areas further east of here and elevated areas especially recieved more than what we did.
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Re: BOM rainfall measurements for Mitcham

Post  hillybilly on Thu Sep 10, 2009 5:38 pm

I think the Mitcham ob for Wednesday is suspect. I would have expected more like 15-20mm - it is possible they got lucky with a storm but I'm not convinced.

Luken you want to get down to Bunnings and buy a Nylex gauge. About $25 and will last you 10 years. They are very accurate (certainly to within a mm or two on most occasions). That's what I use mainly (though do have a Davis tipping bucket rain gauge also for comparison).

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Re: BOM rainfall measurements for Mitcham

Post  droughtbreaker on Thu Sep 10, 2009 7:43 pm

The trusty and humble Nylex is what I use here and they are very sturdy, accurate and reliable. In an even intensity rain band, (good for comparison with other areas), I very rarely get big disparities between my readings and nearby gauges.

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Re: BOM rainfall measurements for Mitcham

Post  Luken on Thu Sep 10, 2009 7:48 pm

The gauge I have is a proper rain gauge. I said above it was a plastic cup with numbers on the side....but it is a genuine rain gauge.

I am convinced something funny is going on with the Mitcham readings, because in the past my figures have been about what I would expect reading what Karl and others get, and the BOM readings from places like Scoresby.

Anyway I appreciate the feed back guys.
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Re: BOM rainfall measurements for Mitcham

Post  Karl Lijnders on Thu Sep 10, 2009 8:23 pm

Luke I am completely certain that observation is suspect as I was watching the weather move up that way all day and really had frequent showers during the afternoon but was on the fringe of the heavier rainband later in the day.

Your obs vs the melbourne water obs suggest a doubling of they're figures to yours. So really halving the totals they have recorded fall in line with what would have occured in the region. Last Friday, that is a massive fall when really the area between Bayswater and Mt Dandenong/Monbulk had the heaviest rainfall. 20mm last Friday is way too high.

Just a thought Smile
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Re: BOM rainfall measurements for Mitcham

Post  Luken on Fri Sep 11, 2009 6:54 am

Well if the figures according to the BOM site are correct then we have had 73m in September already! lol! geek scratch

Wish it was true, but I would say 40mm is more likely. Which even in itself is a very good start to Spring.

Cheers for the comments guys, glad to know that I am not going crazy. Might have to invest in another Nylex gauge just to double chekc things.
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