Rainfall rate to WU

[Praveen Chandrasekaran]

Hi,

I am discussing with Tim Roche of WU over trello on rainfall rate in WU. Ideally I would have liked if WU reported instantaneous rainfall rate than the accumulated rainfall in last 60 minutes. Here is what Tim Roche replied on trello:

Rainfall rate and daily precip are inputs to the PWS data. if they are sent we use them.

http://wiki.wunderground.com/index.php/PWS_-_Upload_Protocol

I have again replied to him with the below:

The PWS upload protocol only has below:

rainin - [rain inches over the past hour)] -- the accumulated rainfall in the past 60 min

This is not instantaneous rainfall rate. This is interpreted as the rainfall accumulated in past 60 mins and sent by weewx to WU. Some details on same in below thread too:
https://www.wxforum.net/index.php?topic=9155.0

I was just wondering if weewx can be hacked/modified to send instantaenous rainfall rates instead of SQLSUM. If so where should I make the changes? (restful.py)

Maybe others here can also chime in on the trello board so that we can sort out this issue. Reporting rainfall over last hour as rainfall rate doesn't make sense. Particularly in tropical areas where we may get short 5 minutes bursts of rains.

Trello board link:

https://trello.com/c/roVxyTpV/29-submit-bug-reports-june-july-2018

Regards,

Praveen

[Andrew Milner]

Rainfall as a rate is some amount of rain per some defined time period.  OK, we can measure the rain quantity - but what is the time period over which the rain has fallen??  Instantaneous would be a time period of zero so would result in zero!!  So do we use 1 second, 5 seconds, 10 seconds, 1 minute, 5 minutes, 10 minutes, or one hour as the time period??  If you use say 10 seconds then I suppose you need to report every 10 seconds (colossal overheads at WU if every staion reported every 10 seconds).  However, if you report every 10 minutes but have a rainrate over a 10 second period, what do you report to WU as the rainrate for the 10 minute period?  You cannot just upload the 10 second rate as over the 10 minute period it would not be correct!!  So, you are almost forced into the current WU arrangement as possibly being the best compromise situation...…..

My view anyway …….

[Praveen Chandrasekaran]

Davis vantage stations report every 2.5 seconds I believe and the rainfall rate is also calculated so. Atleast for stations reporting in rapidfire mode I believe the same value that gets displayed on the console can be sent to WU also?

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[Andrew Milner]

They may be reporting every 2.5 secs, but I believe the rain rate is only updated every 20 seconds.  To make matters worse, looking at the davis comms protocol it is not clear what they actually output - as rainrate is defined as clicks per hour!  Loop2 packets include 15 minute rainfall, hour rainfall, dialy rainfall - all looks quite complex, and that is just for davis stations!!

Have fun, I'm not commenting further.