So let me see if I have got this right.freddie wrote: ↑Sat 28 Mar 2020 8:20 pmIt's the same for days of hail and gale too. Fog is similar to snow depth, in that it is the existence of fog (visibility less than 1000m) at 0900 GMT that makes a "fog day". Snow depth and fog day are measured at an instant in time (i.e. 0900 UTC) whereas all the other elements are measured over a period of time.
In fact, for temperatures it is complicated too. The definition of maximum temperature is that it is attributed to the date on which your meteorological day begins - which sounds reasonable. For minimum temperature, however, it is attributed to the date on which your meteorological day ends. So Cumulus doesn't have it strictly correct. For example - my weather station (via Cumulus) reported at 0900 this morning that the maximum temperature was 13.1, and the minimum temperature was -1.2. Following the definitive rules, the maximum temperature is attributed to the 27th March, but the minimum is attributed to the 28th March. But in the Cumulus "dayfile" they will both be attributed to the 27th. As maximum temperature typically occurs mid afternoon and minimum temperature around sunrise, then you can see why this strange-sounding rule originated.
No, rain days are 0900 to 0900 (UTC). The date the rainfall total is attributed to is the date at the start of the meteorological day - this Cumulus does get correct.
Let assume we are recording at 9am UTC on day 2, what has happened in last 24 hours (since 9am UTC on day 1).
* we record a snow day, or hail day, if there was any snow, hail, (respectively), prior to last midnight
* we record a gale day if there was any wind greater than 47 mph (21 m per second, 41 knots), prior to last midnight
* we record snow depth as at that instant in time (9am UTC on day 2)
* we record fog (visibility less than 1000m) as at that instant in time (9am UTC on day 2)
* we record Maximum temperature, max/min humidity, max wind gust, windrun, min/max pressure, etc. and attribute to day 1
* we record minimum temperature and attribute that to day 2, but nothing else is attributed to day 2?
My script (written for Cumulus 1) for transferring all these weather derivatives to my daily_summary database table actually has 2 rows (day 0 and day 1) of the dayfile.txt log file in PHP variables at same time, so it is easy for me to store correct values to day 1 in the database table as I have access to last 48 hours. I didn't design it for this, the read ahead was so I know when the last day is reached before I process it, and allow time for Cumulus to complete all its rollover actions as by experience I found it initiates the external batch in advance of writing backup files and other file actions.