Rain reports to WU wrong

Something seems to have changed with rain reporting? My Dalyan station has had a small shower of rain. My SmartWeather dashboard shows it correctly but WU shows the rain rate continuing since the start of the shower, but without an increase in the total rainfall.

Rain was between 09.52 and 10.02hrs local.

https://www.wunderground.com/personal-weather-station/dashboard?ID=IORTACA2

Also, a similar issue with my Southsea station. A single event at 06.52hrs but shows on WU as constant rain from 06.54 till 07.59hrs. The only reporting difference is that this station relays via a Meteobridge hub.

https://www.wunderground.com/personal-weather-station/dashboard?ID=IENGLAND451

Has something changed? Any ideas @dsj

I’ve just noticed that this behaviour has been going on for a while, certainly since the 20th September. Seems very odd.

Hi @val . Nothing has changed on our end (although it’s possible Weather Underground changed something on theirs). We report data to Weather Underground every minute with the total accumulation for the day, along with the previous hour’s accumulation. So it’s a rolling one-hour rate value; the total amount of rain collected over the previous hour.

There are other ways to report hourly rate, but that’s what it seems like Weather Underground is displaying for other weather stations. We can’t find any definitive documentation on the value WU expects for “hourly rate”. If you know of any, please let us know!

Surely ‘Hourly Rate’ is the rate per hour, at that moment, not the amount of rain in the past hour?

If you are reporting the ‘total rain in the last hour’ and not the ‘rain rate’, but they expect the ‘rain rate’, that would perfectly explain what is wrong with my WU graphs!

I don’t understand why nobody else has picked up on this though.

If you compare my other Dalyan station
https://www.wunderground.com/personal-weather-station/dashboard?ID=IMUGLADA2

with my WF station
https://www.wunderground.com/personal-weather-station/dashboard?ID=IORTACA2

the issue at 13.30hrs is perfectly obvious.

@dsj This discussion is relevant

http://www.wxforum.net/index.php?topic=31125.0

I would seem that if you want WU to display accurate rain rate information you need to send the ‘rainin’ value as ‘rain rate’ not ‘rain last hour’

If you look on the ‘table’ version of their graphs, I’ll bet the ‘Precipitation Rate’ column is taken verbatim from the ‘ranin’ figure reported.

Thanks for the link! That discussion feels familiar (I think I read it, or something like it, last year) and points out a couple things:

  1. The definition of “rain rate” completely depends on the time reference. The smart weather stations report the amount of rain collected over one minute. This raw value, which is “rain per minute” is not meaningful to most folks, but it’s a valid rate. To make it more meaningful, it can be converted to an “equivalent hourly rate” by multiplying by 60 (how much rain would fall if it rained the same for every minute of an hour). Or it can be summed with the previous 59 one-minute values to provide an “actual hourly rate” (literally how much rain fell over the past hour).

  2. The Weather Underground PWS documentation (before they took it down) defined two values, “rainin” (rain inches over the past hour) and “dailyrainin” (rain inches so far today in local time). That’s what we give them. There is speculation in that thread about how WU converts or displays those values in the graphs, and it’s possible they made a recent change, but from the data we have reviewed today, it looks like they are displaying exactly the values we’re giving them.

4 Likes