The Muzio Discomfort Index (152)

Miles Muzio, KBAK-TV, Bakersfield, CA

John Hart, NOAA-SPC



Extreme heat each summer is measured by a secondary calculation of temperature and humidity- generally the familiar Heat Index used by the National Weather Service. However, an alternate gauge of human discomfort and the potential threat due to effects of high temperature was created in 1976. The Muzio Discomfort Index (MDI) has only been used regionally. Recently, this method was retooled and expanded to include wind chill risk and is now applicable throughout the year in all climates. Unlike other indices which derive &lsquoequivalent temperatures', the empirical MDI sets zero as an ideal value. Departures, either positive or negative, quantify a retreat from ideal atmospheric conditions for human physiology. Summer extreme heat episode intensity is evaluated by Heat Stress Units, in which exceedance of a threshold value accumulates on an hourly basis over a 24-hour period. Similarly, winter extreme cold events also accumulate- in Wind Chill Units. Emergencies of both hot and cold weather are better defined and appraised.While summer calculations utilize temperature and dew point, winter calculations utilize temperature and wind velocity. Winter MDI values are directly linked to heat flux rates on exposed human skin, as expressed in watts per square meter, and match accepted medical definitions regarding frostbite timing. Outbreaks of high heat and extreme cold in 2017-18 are analyzed. Heat indices and wind chill factors are compared to MDI values for perspective.This talk outlines what may be portrayed as a standardized &ldquoall purpose&rdquo thermal physiology threat index.