IMD starts issuing heat index on an experimental basis. Details here

In addition to giving the day’s minimum and maximum temperatures, the heat index, mainly for the plains, will give people “a sense of what the temperature actually feels like”.

During a media workshop on Weather and climate, IMD Director General Mrutyunjay Mohapatra said, “We are utilising the temperature and humidity data at 2:30 pm for the heat index and the forecasts as the maximum temperature occurs at that time.” 

Currently, the weather office uses a formula of the National Oceanic and Atmospheric Administration (NOAA) to calculate the heat index. However, the heat index is yet to be validated for Indian conditions and uses the comfort levels of weather experienced by Americans in their regions.

Further explaining, M Ravichandran, Secretary, Ministry of Earth Sciences said, “We have to work with the health ministry to validate the observations for Indian cities. For example, in India, 40 degrees Celsius temperature and 20 per cent relative humidity could be okay, but the same is intolerable for a person residing in the US.”

The heat index issued by the IMD on Friday carried a disclaimer stating “not validated for India”, making it clear that it was an experimental forecast to educate people about the implications of heat on them. Ravichandran said the index will be issued to make such data more accessible to the public for precautionary measures.

The heat index will be issued for the entire country every day in weather bulletins. The weather office declares a heatwave when the maximum temperature crosses 40 degrees Celsius and is 4.5 degrees above normal for the day. A severe heatwave is declared when the temperature is above 40 degrees Celsius and 6.5 degrees above normal.

Speaking of current temperatures, As per IMD, the national capital on Saturday recorded a minimum temperature of 22.2 degrees Celsius, two notches below normal. The weathermen have predicted generally cloudy sky with very light rain and thundershowers accompanied with gusty winds for Saturday. The maximum temperature is likely to settle around 34 degrees Celsius, it said. The relative humidity was recorded at 48 per cent at 8.30 am.

IMD’s weather forecast for May

On heatwave conditions in the month of May, IMD has predicted parts of eastern India, including Bihar, Jharkhand and Odisha, to face above-normal temperatures in May with a likelihood of heat wave conditions on some days.

However, parts of northwest and west-central India may experience warmer nights and below-normal temperatures during the day, the India Meteorological Department said in the monthly outlook for temperature and rainfall for May.

It said that normal to above-normal rainfall is expected in the northwest and west central parts of the country in May, including in Punjab, Haryana, Rajasthan and parts of western Uttar Pradesh. Large swathes of the northeastern region, Kerala, Andhra Pradesh and south Karnataka, are expected to witness below-normal rains, it added.

According to the weather office, the average rainfall in May is likely to be 91-109 percent of the Long Period Average of 61.4 mm.

“Above-normal heat wave days are expected over most parts of Bihar, Jharkhand, Odisha, Gangetic West Bengal, east Uttar Pradesh, coastal Andhra Pradesh and some parts of North Chhattisgarh, east Madhya Pradesh, Telangana and coastal Gujarat during May,” IMD Director General Mrutyunjay Mohapatra said here.

He said the neutral El Nino prevalent over the equatorial Pacific region is expected to continue through May with a majority of weather models indicating the region beginning to warm up during the monsoon season.

El Nino, or warming of the equatorial Pacific Ocean, is said to have an impact on monsoon rains in India. However, other factors such as the sea surface temperatures in the Indian Ocean (known as the Indian Ocean Dipole) are also known to influence the weather.

Mohapatra said the neutral IOD conditions prevailing over the Indian Ocean are likely to turn positive during the upcoming season. He said positive Indian Ocean Dipole conditions are known to favour the Indian monsoon and help temper the impact of El Nino.

Earlier this month, the IMD forecast a normal monsoon season with 96 per cent rainfall of the Long Period Average of 87 cm rainfall. The weather office is expected to update its forecast towards the end of May

(With inputs from PTI)