The India Meteorological Department (IMD) on Friday began issuing an experimental heat index for different parts of the country that takes into account air temperature and relative humidity.
In addition to indicating the minimum and maximum temperatures of the day, the heat index, especially for the plains, gives people “a sense of what the temperature really looks like.”
“We use the temperature and humidity data at 2.30 pm for the heat index and predictions of how the maximum temperature will occur at that time,” IMD Director General Mrutyunjay Mohapatra said at the Media Workshop on Weather and Climate here.
Currently, the weather station uses the National Oceanic and Atmospheric Administration (NOAA) formula to calculate the heat index. However, the heat index has yet to be validated for Indian conditions and uses the weather comfort levels experienced by Americans in their regions.
Temperature of 40 degrees Celsius and 20 percent relative humidity
“We need to work with the health ministry to confirm the sightings for Indian cities. For example, in India, a temperature of 40 degrees Celsius and 20 percent relative humidity might be fine, but the same is intolerable for a person living in the US,” said M. Ravichandran, Secretary, Department of Earth Sciences.
The heat index released by the IMD on Friday carried the disclaimer “not verified for India”, making it clear that it was an experimental forecast to educate people about the effects of heat on them.
Ravichandran said the index would be released to make such data more accessible to the public for precautionary measures. The temperature index will be issued for the whole country every day in weather bulletins. The Met Office declares a heat wave when the maximum temperature exceeds 40 degrees Celsius and is 4.5 degrees above normal for the day. A severe heat wave is declared when the temperature is above 40 degrees Celsius and 6.5 degrees above normal.
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