First, let me apologize for hijacking this Belchertown thread to get educated on Apparent Temperature.
Second, thanks Gary, your explanation clarifies it for me. It seems I was fixed on a simplistic definition of Apparent Temperature sometimes used in the US which yields the same value as either Wind Chill, Temperature, or Heat Index depending upon the value of "actual temperature". In contrast, the weewx calculation relies on the more sophisticated model developed by Steadman. I actually like that the weewx calculated value is different than what I thought it should be. The simplistic definition doesn't add any new information as you could just look at Wind Chill, Heat Index and Temperature to get the same information the simple definition provides. In addition, I don't actually know what formula Vantage uses to calculate Wind Chill and Heat Index (I'll look it up), which my station hardware calculates and provides. The Steadman model gives a more nuanced value probably closer to what is intended - that is, what the human body perceives the temperature to be. I'll move any further questions I have on this to a separate topic. phil On Sunday, December 9, 2018 at 6:05:08 PM UTC-5, gjr80 wrote: > > As you point out weeWX windchill and heatindex values track outTemp below > certain minimums and above certain maximums respectively. The weeWX > calculated appTemp uses the formulas mentioned in the post you linked and > is quite different to a composite heatindex and windchill (by composite I > mean windchill below 50F and heatindex above 81F). The key difference > (other than the formula) is that appTemp is valid across all temperatures. > appTemp is certainly affected by wind speed (just look at the formula), I > often notice appTemp moving in time (and quite markedly) with wind speed > changes on my realtime gauges. > > I like to think of 'feels like' as being a term that means different > things to different people and without an agreed understanding can be a > source of confusion. It really is just a general term that tries to better > approximate the effect of current weather conditions on the body, it could > be based on a measure of heatindex, windchill, humidex, wet bulb globe > temperature or apparent temperature. For me in Australia I think of > apparent temperature, I expect in Canada humidex may be a more accepted > measurement. > > The use of the term 'apparent temperature' can also be confusing at times; > does it refer to the accepted formula for Apparent Temperature (as you > linked or as used by weeWX) or is it the more literal meaining. For this > reason I prefer to refer to something like the 'weeWX appTemp field' or > 'Apparent Temperature' to make it clear I am referring to the calculated > value. > > Gary > > -- You received this message because you are subscribed to the Google Groups "weewx-user" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
