Heat Index Display

[Sunfish]

My Vue ISS is currently sending the outside temperature to the console as 71 degs F.

However, the Heat Index in the console display, is only 68 degs but the Cumulus software program, which uploads to the web, is the same as the outside temp, 71 degs. Surely, the readings should all be identical?

WU shows the Heat Index figure as 78 degs!

Why the discrepancy between the console, Cumulus and WU, the latter using data from my location?

[steve]

Cumulus doesn't use the heat index from the console, it calculates it itself using the formula described here:

http://www.hpc.ncep.noaa.gov/heat_index ... ation.html

(I actually use the code provided by Steve Hatchett, here - http://www.softwx.com/weather/uwxutils.html)

For temperatures below 80F, heat index isn't calculated, and Cumulus displays the same as ambient temperature. The console clearly doesn't apply this rule (I believe Davis use an adapted heat index formula that ends up being more like an 'apparent temperature', so it can be lower than ambient temperature).

Weather Underground doesn't have heat index as part of its upload protocol, so it is presumably calculating the heat index itself. You would have to ask them what formula they use.

[Sunfish]

How very interesting.

Thanks for the comprehensive explanation.