2021-08-04, 12:44 PM
(2021-08-04, 08:20 AM)DAW89446 Wrote: I thought this an interesting statistic, as quoted from the Sierra Wave News (Bishop):
The hiker is thought to have set off on Sunday or Monday in 118 degrees Fahrenheit heat with
up to 91 percent humidity due to scattered showers. To give readers some idea of how “hot”
that combination of extreme hot temperature and very high humidity “feels,” according to the
National Weather Service Heat Index Calculator, it is the equivalent to the body feeling the
temperature of 320˚F (160.4˚C).
This is a classic example of garbage in/garbage out calculation and reporting, however.
118F with 91% humidity is essentially an impossible weather phenomenon as it results in a dew point of 115F while the highest ever recorded dew point on the surface of the earth was 95F in Saudi Arabia. The reporter has combined the maximum temperature of the day along with the maximum relative humidity of the day which did not occur simultaneously. Relative humidity is *strongly* dependent on temperature for a fixed amount of water vapor in the air. If you pick relative humidity from a cool part of the day and combine it with the air temperature from a hot part of the day you get nonsense.
Next the reporter went and threw the garbage numbers into a calculator that simply extrapolates heat index values beyond where the model even makes any physical sense. The heat index model is meaningless in these non-physical regimes which is why if you look at NWS tables of heat index they don't even report numbers beyond certain combinations of temperature and humidity.