# Rain Intensity vs Accumulation

Hi

Can someone explain to me the relationship between Accumulation and Rain Density. I have periods where I am showing Rain density bars on the graph but the Accumulation total does not got up.

you better have a look at the rain rate graph instead. These bars already show up with a very minimal amount of rain, and don’t represent the actual rain rate.

Okay so here is the rain rate graph, but the same question what does the bar actually mean, the heading says rate per hour, but how long is the bar duration. I ask as if you add the durations they should effect the total and the two don’t seem to match
?

yes it is indeed. The numbers on the left represent the rain rate in mm/hour, for the given width of the bar. They also give the accumulated rain. So the vertical axis has a double meaning in this graph.

look at the first half hour. each bar is 5 minutes wide. The first has a value of 0.5 mm/h That is if you had 12 of these 5 minutes intervals you would have accumulated 0.5 mm. But you only have 1 bar so the total accumulated rain for those 5 minutes is 0.5/12 mm.
So for the first half hour the total accumulated rain is about (0.5+2 +6.5+1 +0.2+ 0.7) /12 = 0.9 mm. Which seems to match the increase in the accumulated rain for that period.

Okay thanks, my problem is that the rain gauge is not showing anywhere near the correct values for rain accumulation. Today we have had several large rain storms, nearby sensors have shown over double the rain as recorded on my tempest

o, but that is a totally different problem. That might be a problem with the calibration.
if you have correct values, you might submit them online
" In an effort to bring a little structure to the process of collecting and acting on your “SKY vs. co-located rain gauge” reporting, we’ve created two Google forms, one to Register your Co-located Rain Gauge and another to Report Accumulation Data "
After enough values are gathered, a calibration should be applied automatically.

Weatherflow say they are looking at it but no change yet. They say they are waiting for good values, well there is enough around me, so I was hoping they could calibrate it quickly.

I have had my Tempest now for a month and really want to know if these problems can be fixed, because if they can not then I want to return it and I am running out of time in the 60 day window.

What I’ve learned so far is that you should expect accumulated rain values to be very exact. Your difference might be too much, so calibration should fix that.
Edit: big oops as I meant to say “shouldn’t expect”

I would be happy if it was within say 10-15% but these figures are to far away.

Weatherflow doesn’t use nearby stations as they have no idea in how far they are correct or even worse than yours. Even a Davis VP2 can give about anything if not set correctly or maintained (leaves getting in the tipper for ex). I have one about 2 km in line from me and the one thing I know, its values are useless.

In the US there is the raincheck option since Weatherflow has access to accurate satellite data for ex. For now other parts of the world are not covered by this system (hopefully one day)

As mentioned by Sunny, try to use a manual gauge and submit data via the report. Over time that data will be taken into account and will help to calibrate your device. For now it is the best option knowing the haptic sensor isn’t perfect under all circonstances. This method takes time but it works.

Would you have a recommendation for a manual gauge, it needs to be wireless obviously.?

believe it or not I use this

You can use about anything as long you can get totals with exact time frame as you report day x from time y to time z : nnn mm

I have no specific brand to propose for electronic devices but see that there is at least some calibration option (something like using x drops to make the spoon tip ) even those things need calibration from time to time. But don’t go spend fortunes on it.

just search for rain gauge and you’ll find several shops in the UK proposing many models

Do you know how many readings per day Weatherflow need to have calibration data. It’s rained all day here, so going out in the pouring rain ever 30 minutes is not a welcome prospect

I gave 1 a day on average for the 24 hour period. And at some point during lockdown I did several a day but waited each time the shower stopped since you give with a time frame they can re construct since they have the signal, they work to match the total you give.

Thanks will give it a try.

I’m also wondering about my Tempest. We had some rain yesterday and last night, but my weather station didn’t register anything.
Any suggestions as to what I need to do? I’ve contacted Tempest, but no response yet.