Hmmm... Not entirely sure. I can't seem to figure out the rain units the station is using, although the actual pattern seems correct. OregonScientific cloud service seems a lot more stable these days and makes it easier to try and correlate the data.
So I decided to go with rra and just use the difference between each reading like you suggested. This seems to produce the correct graph based on the actual amount of rainfall, but on the wrong scale. (I'm using metric btw.).
I figured may be the station is reporting the rain in inches looking at the delta values produced (they're fractional with 2 decimal places). So I simply converted to mm before giving it to weewx as 'rain'.
Yesterday and last night we had some serious rain so I attach the graph from weewx and what the OregonScientific cloud server recorded for my station.
Here are the values extracted from Oregon:
All data are in 5 minute block.,,,,
utc,date,time,rainrate (mm/h),rainfall (mm)
On the graph you can see weewx recorded about 170mm between 16:00 and 17:00. The weekly stats page says the highest is 527.3 mm/hr at 16:53:43 (Wednesday) which is way off.
OregonScientific only shows total rain on its graph, but from extracted data above, the peak is 27.8mm/h with 25.4mm total for that period.
I have the original raw values for those times, but they're not of much help to me to figure out the difference in readings.
I'm pretty sure I need to stop converting the output from the station and leave as is.