Topic: There are a lot of unused CoCoRaHS gauges around.

[George Richardson]

I don't know what to politely say about the study! (here's a study that compares the accuracy of the 4" plastic CoCoRahs gauge with the standard NWS 8" metal gauge) While trying to calibrate my Davis See-Saw against the 4" standard, I'm not interested if we don't have over 1/2" rain with low winds in a 24 hour period. While you can read the 4" gauge to the closest .01" that could be 25% to 50% error per day in the amounts of rain they were getting at the test site. I don't care if the study was 100 years, in my opinion it was a bad test.

Sorry, had to rant!

George

[blackjack52]

Definitely not a solid test.
Especially the explanation for deviations throughout the months; some months 0 dev, and in Jul.  What, no wind in Jul in CO   Guess what, when the storms come over the Rockies and hit that hot moist air in the valley, there's alot of wind. Over a 10yr period, there should be a better explanation.

[wxtech]

Dr. Nolan Doesken, founder of CoCoRaHS, has decades experience with the 4" rain gauge.  The CoCoRaHS data is used for climatology and research.  So the database must be consistant with only one type of rain gauge in use. 
I use the 4" plastic, the 8" SRG, the Fischer-Porter and have a WaterLog H-340 connected to my Davis.  The Davis tipping bucket under reports an average of about 15%.  I can adjust for light to medium rains and be accurate, or accurate at high rain rates, but not accurate at low and high rain rates.  The problem is splatter and loss of water as the bucket is tipping from bucket to bucket.  It can't possibly be as accurate as a bucket with a ruler.

I'm a CoCoRaHS county coordinator.  I enter observers rain amounts when they aren't able to do it themselves.
 
I've also specified the 4" rain gauge when I set up a county rainfall reporting network in 2006, prior to Ga joining CoCoRaHS.

By-the-way, the little plastic screen that fits over the bottom hole in the Davis funnel is vital to your rain measuring accuracy.  It screens debris but most importantly, it is an anti-vortex screen.  It prevents swirling of the water as it flows fast from the funnel to the buckets.  Swirling causes splatter and less accuracy.

[LFWX]

We've only had CoCoRaHS for a short time here in Ohio and of the 4 stations registered in Butler County only 2 of us are reporting anything. That's only 50% and we just got started. My work schedule (and sleep habit) doesn't make 7:00am a nice time for me, but I get up any morning it has been raining and check the rain collector.

By-the-way, the little plastic screen that fits over the bottom hole in the Davis funnel is vital to your rain measuring accuracy.  It screens debris but most importantly, it is an anti-vortex screen.  It prevents swirling of the water as it flows fast from the funnel to the buckets.  Swirling causes splatter and less accuracy.

That's something I never thought of. Mine blew away when we had a wind storm last fall http://www.erh.noaa.gov/iln/sept14_2008/sept14wind.html I just wish Davis didn't charge $2.00 for them.

Note the antenna mast after the wind storm (next time WILL be different)
http://www.flickr.com/photos/30112397@N06/sets/72157607366139110/

My Davis seems to over report in heavy rain, I've assumed the steep, deep, walls of the Davis caused less splash than the short walls and 45 deg. angle of the funnel of the CoCoRaHS collector. I'm building an analog collector using a Davis funnel to check that theory.

[tomcj2]

My work schedule (and sleep habit) doesn't make 7:00am a nice time for me, but I get up any morning it has been raining and check the rain collector.

CoCoRaHS prefers all participants to report at 7:00AM, but you can choose any time that is convenient  for you.  It is probably better to report at the same time each day, I report at 5:45AM each morning.  I e- mailed them and they changed the default time on my reporting page so I did not have to manually input it each day. 

You should report all days, rain or shine. The following is an excerpt from a recent e-mail from Nolan Doesken, the National Director of CoCoRaHS.

2) /*Do I have to report on days with no precipitation*/?

The answer is "No", you don't have to, but "Yes" we really hope that you
do. Unless you tell us it did no rain, we won't know for sure. For many
reasons, like drought monitoring, knowing that it did not rain is just
as important as knowing that it did. So if you can, please report. Also
stations with complete data are more likely to be used in research and
climate monitoring than stations with incomplete records. Remember, you
can use the "Monthly Zeros Report" to make it easy to fill in the zeros


Thank you for joining this very worthwhile project

[LFWX]

You should report all days, rain or shine.

I agree, and do report every day, since the weather computer is in the bedroom it's just an arms length away.

Thank you for joining this very worthwhile project

Glad to be a part of it. Hope to see others in the area join in.

[port1]

   I report every day, even trace precipitation and zeros.  But, what's just as important to CoCoRaHS is snow accumulations, and measurement of melted snow.  Info that's valuable to climatologists.  There's just no way to get that info without that manual measurement with the CoCoRaHS ruler (measures in tenth's of an inch) off a snowboard.  Afterwards, I use the same data to report the snow depth to SKYWARN.
You should all try it.  It's very rewarding, and it takes less than a minute.  Data entry on the home page is real fast!  You can read your gauge as you leave for work, and wait to enter the data later from any computer. 

[Cienega32]

By-the-way, the little plastic screen that fits over the bottom hole in the Davis funnel is vital to your rain measuring accuracy.  It screens debris but most importantly, it is an anti-vortex screen.  It prevents swirling of the water as it flows fast from the funnel to the buckets.  Swirling causes splatter and less accuracy.

What is your opinion of using one of those kitchen strainers (as a few of us here do) in the Davis bucket as far as the anti-vortex properties?

I gave up on the Davis screen after finding it nowhere near the station. Rain here usually comes with 25+MPH winds and those 40+MPH gusts always throw the strainer out.

[d_l]

I gave up on the Davis screen after finding it nowhere near the station. Rain here usually comes with 25+MPH winds and those 40+MPH gusts always throw the strainer out.

I made a screen "leash" out of a stainless steel ligature wire (orthodontic wire).  At least now when the winds, the Washoe Zephyrs, blow the screen out of the rain cone, it isn't lost to me.  ... and they blow hard enough nearly every day to do so.  Whenever I expect rain, I have to remember to put the screen, which is usually dangling on its leash, back into the cone.  That's a nuisance chore, but it doesn't rain that often.

[DanS]

I made a screen "leash" out of a stainless steel ligature wire (orthodontic wire).  At least now when the winds, the Washoe Zephyrs, blow the screen out of the rain cone, it isn't lost to me.  ... and they blow hard enough nearly every day to do so.  Whenever I expect rain, I have to remember to put the screen, which is usually dangling on its leash, back into the cone.  That's a nuisance chore, but it doesn't rain that often.

Would it be possible to use a fishing weight under the screen but high enough not to obstruct the funnel opening?

[sam2004gp]

I used fishing wire on mine to keep it from blowing away.

[port1]

The fishing line isn't a bad idea, but it likely is not U.V. stable, and may degrade.  Don't know exactly.
I did the same, and then changed out to an all vinyl twist-tie that came with some packaging, and I haven't lost my screen yet.
(about three years). 
All good ideas...none that shouldn't be considered.
So long as you keep your screen...that's all that matters, eh?
 

Seriously, though....consider joining CoCoRaHS.  They really need the volunteers, and the reporting is so easy and convenient.
Example:
Had to run to work this morning, and had no time to send my data.
I glanced at the gauge as I ran by....this time it was empty...no rain last night.  Easy to remember.
But, I only made my data entry at 6:00PM when I got home from work.  No worries!
As long as your observation is consistent, and it doesn't have to be to the split second each time every day...you're good to go.
Try it, man! 

Plus, it will help you keep track if your electronic gauge is close.
So easy....don't let the commitment intimidate you.

Henry

[sam2004gp]

The fishing line isn't a bad idea, but it likely is not U.V. stable, and may degrade.  Don't know exactly.

Actually this fishing line is, I purchased the roll originally for the wife to easily hang some small Christmas Wreaths during the holiday season.  I purchased UV-effects proof line.

[port1]

Way clever...good idea.
Light and wispy too...won't interfere.
You're good to go. 

Henry

[Cienega32]

I've yet to lose the big strainer on my VP2 but that Davis one... sheesh! Last time, it went missing for months and turned up about 30 or so feet away - maybe more/can't remember but I know it took me days to realize what it was.

port1: that was the whole idea - to double check the tip buckets and I've always liked the idea of the CoCRaHS program but...

Anyway, the more I read about people faced with the same "problems" as me, the more it seems I might be able to handle it. And the easy entry 'zero' readings appear to be key. With the few rain events I get, I would easily tire of entering ZERO on a scheduled, daily basis - especially being a bit of a nite-owl.

It's not so much that the commitment is intimidating as much as I don't want to be an unreliable member or skew the overall numbers because of it. The 'negative impact' concept...

After reading about everyone's experiences/reporting styles, I have a hunch I'll end up doing it... sooner than later.

[Anthony]

This thread seems to be drifting to a different topic that what it started out to be. Maybe one of the other moderators with a little more power that me needs to move the last several posts to a new topic? Just a thought.

[Chris H.]

I'm guilty of failing to report, but New Mexico is only new at this, and not very many people joined..plus I'm a little lazy at the reports when it does rain. My desktop takes 3 minutes to boot up, and I guess that isn't bad since I get up at 5:30am and leave for school at 6:10am. But during breaks (Winter break, spring break etc..I usually don't get up til like 10..hee hee)..I'm also wanting another PWS with a rain bucket..my first one had to go when the anemometer broke..but I did testing on it and compared it to a standard SKYWARN issued 4" acryllic and found the tipping bucket to have a +- 5% margin of error.

But..I plan on getting a second PWS with a PC connection..and I want rain fall history..rain only occurs about 15% every month..unless it's a heavy monsoon/El Nino year..or we get the occasional severe storm between September and May...

Okay..I'm done getting off topic. Anybody have an idea for a homemade hail pad?

[tomcj2]

CoCoRaHs has instructions here http://www.cocorahs.org/Content.aspx?page=howtomakehailpad

[Chris H.]

Recently got about 1.40 inches of rain in less than an hour from a nearly-stationary thunderstorm last week that dumped a ton of rain. Glad I had put out there before the rain fell after cleaning it!