asthut Posted June 13, 2012 Share Posted June 13, 2012 Does anyone have a formula to calculate heat index based on temperature and dew point. I have a large excel file where I am trying to convert to heat index from these two variables. Any help would be appreciated! Link to comment Share on other sites More sharing options...
Ed Lizard Posted June 13, 2012 Share Posted June 13, 2012 Maybe this? http://www.srh.noaa.gov/epz/?n=wxcalc_virtualtemperature Link to comment Share on other sites More sharing options...
Billabong Posted June 13, 2012 Share Posted June 13, 2012 Does anyone have a formula to calculate heat index based on temperature and dew point. I have a large excel file where I am trying to convert to heat index from these two variables. Any help would be appreciated! Things get complicated when getting down to the formula for heat index. You can use this excel equation which is a good approximation... =ROUND(16.923+((1.85212*(10^-1))*A1)+(5.37941*B1)- ((1.00254*(10^-1))*A1*B1)+ (9.41695*(10^-3)*(A1^2))+(7.28898*(10^-3)*(B1^2))+ (3.45372*(10^-4)*(A1^2)*B1)- (8.14971*(10^-4)*A1*(B1^2))+(1.02102*(10^-5)*(A1^2)* (B1^2))-(3.8646*(10^-5)*(A1^3))+ (2.91583*(10^-5)*(B1^3))+(1.42721*(10^-6)*(A1^3)*B1)+ (1.97483*(10^-7)*A1*(B1^3))- (2.18429*(10^-8)*(A1^3)*(B1^2))+(8.43296*(10^-10)* (A1^2)*(B1^3))-(4.81975* (10^-11)*(A1^3)*(B1^3)),0) A1 would be temperature (°F) and B1 would be relative humidity (in percent). Link to comment Share on other sites More sharing options...
kylemacr Posted June 13, 2012 Share Posted June 13, 2012 The formula for heat index is on the wikipedia page: http://en.wikipedia.org/wiki/Heat_index . The formula on there requires relative humidity in percent ®. You can approximate it from T and Td using the approximation for relative humidity shown here: http://www.ajdesigner.com/phphumidity/dewpoint_equation_relative_humidity.php . Since relative humidity is really a ratio of vapor pressures and not temperatures, it's only an approximation but it should get the job done! Good luck! Link to comment Share on other sites More sharing options...
lakeeffectkid383 Posted June 13, 2012 Share Posted June 13, 2012 This might help... Left side chart? http://www.hpc.ncep.noaa.gov/html/heatindex.shtml Link to comment Share on other sites More sharing options...
asthut Posted June 14, 2012 Author Share Posted June 14, 2012 Thanks for the replies. I was hoping I could get straight from temperature and dew point to heat index. However, to do this in a larger scale, it looks like I will have to compute the RH first and then the heat index. One extra step, but it will get the job done! Link to comment Share on other sites More sharing options...
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