Cumulus Support

Since this is my first full year using Cumulus MX, the last few days are the first that we've reached the 100 degree mark.

What I've noticed today (just started today) is that the heat index reads the same as the air temp when the humidity is less than 40 percent. Even if the computation for heat index indicates that it's higher than the air temperature.

It's tough for me to know if it has done this when the air temp is less than 100, but I intend on rooting back through my data to see if I can find a case of this. Right now, my humidity is hovering right around that 40 percent mark. Once it gets to 40 percent and above, the HIs look correct...but once it's below, it matches the air temperature. I'll try and get a screenshot of this data as well.

EDIT: Looking through my data in MySql it does appear that this happens once the humidity is below 40 percent.

It's intentional. Heat Index is generally regarded as not valid when the RH is below 40%, and MX implements this. I do note, however, that Cumulus 1 does not implement this cutoff. The Wikipedia page on Heat Index mentions the cutoff, but it also mentions this page http://www.iweathernet.com/educational/ ... sion-table which refutes the 40% cutoff value.

If there is an "official" statement somewhere that the 40% cutoff can be ignored, I'll remove it from MX.

Edit: I found this thread regarding the formula used in Cumulus 1 - https://cumulus.hosiene.co.uk/viewtopic.php?f=4&t=3177 - so I guess I could look at doing the same thing in MX.

steve wrote:It's intentional. Heat Index is generally regarded as not valid when the RH is below 40%, and MX implements this. I do note, however, that Cumulus 1 does not implement this cutoff. The Wikipedia page on Heat Index mentions the cutoff, but it also mentions this page http://www.iweathernet.com/educational/ ... sion-table which refutes the 40% cutoff value.

If there is an "official" statement somewhere that the 40% cutoff can be ignored, I'll remove it from MX.

Edit: I found this thread regarding the formula used in Cumulus 1 - https://cumulus.hosiene.co.uk/viewtopic.php?f=4&t=3177 - so I guess I could look at doing the same thing in MX.

I didn't mean for you to have to do extra work Steve as I know how much time this must consume for you. In doing the queries for my specific station, out of about 115,000 records at 5 minute intervals, this affects about 700 records. I wasn't aware of the 40 percent cutoff, however I suspected that might be what it was. I wish Heat Index was more standardized around the world.

Thank you for looking.