Cumulus Support

Neil:

You really need to rotate the thermo/hygro sensor arm away from the wall, if only to clear the disrupted air flow of the roof.

beteljuice wrote:Neil:

You really need to rotate the thermo/hygro sensor arm away from the wall, if only to clear the disrupted air flow of the roof.

It hasn’t as yet had any effect on the readings but I suspect you’re right and I will move it when I carry out my other plans for the site.
Thanks for the heads up.
Looking at the time of your posting you either work shift, suffer from insomnia, need very little rest or none of the above.

I must say this has been, all in all, a fascinating thread to follow ........................ and the guide Jim has pointed us to is well worth a read.

I've had my AWS since last May and have suffered most of he issues raised here, with the wind (a large deciduous tree nearby) and the temperature (16C recorded last - sunny - Saturday afternoon) issues still to crack. As our local Primary School takes a feed from the station I'll have to do something

Knowing your great carpentry skills Geoff, I don't see you having any problems with most of the recommended mods. You are clearly very capable with DIY tools

BTW, I've added some info about my mods on my weather web site and will be adding more details and photos in due course.

Having read through the word document and several PM's with othre members, I'm wondering if we (meaning the general membership) often get too obsessed with these things. Whilst I note the comments that cheap recorders properly calibrated are better than having precise recorders out of calibration, I think that we still need to step back and take stock of the fact that these F/O type stations are mass produced in the far east and are a compromise between resolution and practicality to meet a pricing point.

We strive to get true / best readings when placing the sensor array around the home, be that on a pole, attahed to a building or above a shallow pitched roof, but for those of us in suburbia we are always going to have obsticles and oter practicalities that will make it impossible to mirror the results from true met office stations. I think that some of the mods that members have applied are interesting, and may well result in "better" or true readings, but at what sacrafice do we go to to get these results. I was going to spend a fair bit of money to have the trees cut down by 10' due to my obsession with not having "true" windspeed readings until I received a virtual slap in the face from a member who said I was mad to do this for the sake of thinking it was he right thing to do to resolve my "issue". On reflection he was right, and even when I reposition the array using the 8' pole, no doubt someone will comment that the turbulance from he trees will screw up my readings... but so what... This is just a hobby, and it still gives me a general idea what the wind speed is and the direction its coming from. If I lived on a farm in the middle of knowhere then things would be different, and I would probably erect a 10m pole for the sensors and place them in the middle of a field, but I don't. I live in the middle of a town with houses all around, loads of large trees, and have the folks next door to consider, who would probably object to a large pole visible from their bedroom window. Therefore I have to make do with what i've got and enjoy what information the current installation has to offer me.

[/rant off !]

Malc_C

Re your last remarks about wind and turbulence from obstructions. I completely agree about keeping things in proportion and hobbies and such. At first, I was a bit narked that my most practicable mounting position led to my wind direction and probably wind speeds being a bit compromised. This was made worse probably by the lack of tail drag on the Watson wind vane. However, downloading the beta release of Cumulus, clicking the average option, and setting the averaging period to ten minutes in cumulus ini, has really brought the skittish wind vane to order as far as the results go. I may still be getting a somewhat skewed direction indication, but it is comparable with nearby stations. I think the buffeting from eddies around a nearby tree makes my wind vane suspect, but it certainly beats creating a 35 foot, free standing tower at the bottom of the garden. I'm actually very happy with the way the Watson has worked now I've sited the temp sensor out of the sun. That was achieved for less than £8 by fitting an RJ11 extension lead to give me more options than sticking it up in the sunshine.

I mean, basically we know that if the wind comes in any point from the north it is going to be colder - right? Who cares of it is 350 degrees or 5? Maybe I have a bad attitude though. Some of my old teachers wrote that in my school reports.

Totally agree with your sentiment - it's a hobby and our lives, fortunately, don't depend on it.

But tinkering can be such fun!

Really, if you've got a choice of locations, having some idea of what works and what doesn't so you can make an informed choice is a good thing. Beyond that, madness lies.

Jim, I agree that tinkering can be fun, and often can improve the results. But sometimes I think there is a point where you need to step back and tinker no more.

I'm not pointing fingers or accusing anyone, and I'm not in anyway judging, but who's to say that using a fan assisted Stevenson screen made from large bowls is going to give true results or adjust them too much the readings are low. Who's to say that adding filter screens to the rain gauge doesn't reduce or restrict the amount of rainfall. - The fact of the matter is that unless you have a calibrated met office weather station in the exact same location, you have nothing by which to calibrate your own mass produced station.

I think that regardless of where sensors are located, the results from day to day will be retrospective. EG, if Monday is sunny and hot, and the max temperature the station records is 20C and then on Tuesday it records 22C, then would that not dictate that Tuesday was 2 degrees hotter than Monday, even though the "official" temperature may well be 18 and 20 for each day respectively (if you follow my drift).

I guess that if you have one of the more expensive stations costing several hundreds of pounds, then positioning of the sensors may well be more critical, but then again anyone who spends £500 - £1000 on a home weather station is someone who I class as a serious enthusiast rather than a casual hobbyist who has only parted with £70 for his kit.

... a casual hobbyist who has only parted with £70 for his kit

Interestingly enough, over various forums, I find that these are exactly the people demanding to know eg. baro pressure to 0.01 hPa, why can't they measure a 'drop' of rain, and by the way "Why does my weather station have the wrong picture for the weather".

Then, because we are all closet Einsteins, we invent modifications, create software and eventually realise we should have bought a webcam

Well guys, it's been a busy afternoon.

I took delivery of an 8' mast and a hand full of clamps this week, and (between the odd threatening shower /sleet) managed to modify my sensor installation. Here's the result



The bracing of the wood is quite strong and the pole being light means there is very little movement, however I'll have to wait until we have a really windy day to see if I need to attache any further bracing or guy wires. I have also moved the rain gauge down so that any vibration do not cause incorrect readings.

The good news is that no trees were harmed as a result of this installation

Very nice Malcolm it looks very sturdy but don't forget to adjust your elevation..... only joking

One thing I might do is move the temperature array up a foot or two, so that it isn't affected by radiated / reflected heat off the shed roof, at least to lesser degree -