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Longest Dry Run curiosity

Posted: Thu 26 Jul 2018 4:58 pm
by patchpeek
My Cumulus "Longest Dry Period" ended at 31 days, when we had 0.6mm on the 21st July. However whilst listening to a BBC weather man on Radio 4 talk about some areas experiencing 45+ days continuious days of no rain, he said that rain less than 1mm does not officially count! I was very suprised. Did i hear that right ? I would be on 46 days if the brief shower was excluded....

This seems to suggest,if true, that the Cumulus Software defintion of "Dry Run" or the default "RainDayThreshold" might not be quite right perhaps.

This is not a complaint and I don't have an issue; it works as I expect and want. Perhaps you are aware or not, either way, I just thought I would throw this up here out of curiosity.

Best Wishes.

pp

Re: Longest Dry Run curiosity

Posted: Thu 26 Jul 2018 6:09 pm
by steve
I'm pretty sure that the Cumulus default of 0.2mm corresponds to the official definition of a dry day as defined by the Met Office and/or the WMO, or at least it did at the time I wrote the code. See this page, for example: https://www.metoffice.gov.uk/climatecha ... daily.html

Perhaps the definition has changed. But 1mm is quite a lot of rain, I don't think I would regard that as a dry day myself.

Re: Longest Dry Run curiosity

Posted: Thu 26 Jul 2018 7:08 pm
by dazza1223
note just me then have the same thing min say 12 off may last time we hade rain but it saying Days Since Last Dry Day 44 Days but it ment to be over 60 days now

Re: Longest Dry Run curiosity

Posted: Thu 26 Jul 2018 7:12 pm
by steve
dazza1223 wrote:note just me then have the same thing min say 12 off may last time we hade rain but it saying Days Since Last Dry Day 44 Days but it ment to be over 60 days now
This is nothing whatsoever to do with that.

Re: Longest Dry Run curiosity

Posted: Thu 26 Jul 2018 7:18 pm
by RayProudfoot
steve wrote:But 1mm is quite a lot of rain, I don't think I would regard that as a dry day myself.
I agree. That's 0.04" in old money. I set the trigger at 0.01" as I can get quite a few days with dew recorded.

Re: Longest Dry Run curiosity

Posted: Thu 26 Jul 2018 7:18 pm
by dazza1223
o sorry my bad i just re read it sorry steve