IMD predictions and reality in India

In India, where rain-fed farming dominates the agriculture sector and farmers sow seeds based on the IMD forecast, the institution's capacity to accurately forecast weather in a small geographical area needs to improve drastically and the weathermen should be held accountable for causing stress to farmers and people at large by providing an incorrect forecast.

Hyderabad: The Government of India established the India Meteorological Department (IMD) in 1875, bringing all meteorological work in the country under a central authority. The IMD introduced SSLRF (Second Stage Long-Range Forecast) in 2003, after the failure of FSLRF (First Stage Long-Range Forecast) to predict the massive drought of 2002. Out of the 24 years since 1995, FSLRF over-predicted rainfall in 13 years and under-predicted it in 11 years.

What information does IMD provide?

The India Meteorological Department's southwest monsoon forecasts provide critical information to at least 700 million people in India who depend, directly or indirectly, on agriculture for a livelihood.

The weather department issues five kinds of forecasts. Nowcast is for less than 24 hours. The short-range forecast is for up to three days. The medium-range is from three to 10 days. The extended-range is for 10-30 days. The long-range is on a seasonal scale (e.g. monsoons).

These forecasts are used for various enterprises, such as agriculture, transport and water management. The forecasts are generated with the help of weather models. Over the years, the meteorological department has moved from crude to a mix of crude and advanced models to predict the weather.

How does IMD predict the weather?

IMD issues operational long-range forecast for the rainfall during South-West Monsoon Season (June- September). These forecasts are issued in two stages. For this purpose, IMD uses the seasonal forecasting model (SFM) developed at the Experimental Climate Prediction Center (ECPC), Scripps Institute of Oceanography.

As much information as possible is gathered about the current weather and the state of the atmosphere. The observations, such as temperature, pressure, humidity and wind speed, are collected from across the globe and then fed into powerful supercomputers.

The five categories probability forecasts for the Seasonal (June to September) rainfall over the country as a whole based on the SEFS forecast are given below, which suggests the maximum probability for monsoon seasonal rainfall to be normal (96-104% of LPA).

IMD predictions go wrong with Monsoon forecasts

Data from the previous 16 years shows that IMD's first monsoon forecast was mostly at a large variance from actual rainfall values. From 7.94% between 1995 and 2006 to 5.95% between 2007 and 2018. Even so, over the last 11 years, the actual rainfall matched the forecast only half the time.

For Instance

• Since 1988, in the last 23 years, the IMD has been able to successfully predict the monsoon only nine times – a success rate of just 40 per cent.
• In 2007, IMD had forecast "below normal" rainfall of 93% of the long-period average (LPA), but the rainfall India received was "above normal" at 106%.
• In 2009, IMD again predicted below normal rainfall of 93% of the LPA, but the actual rainfall was only 78%, which belongs to the "deficient" or drought category.
• In 2014, the India Meteorological Department faced criticism for its outdated prediction system after Uttarakhand experienced unexpected, heavy rainfall and cloudburst.
• In 2016, IMD predicted "excess" rainfall, which in actuality turned out to be average.
• In 2018, IMD was off the mark, having predicted 97% of LPA when the country received rainfall that was 91% of the LPA, the average for 50 years. In 2018, for the first time, India received rainfall of less than 80% of LPA.
• On February 11, 2018, a hailstorm had affected several villages in central Maharashtra and Vidarbha, destroying standing crops in Marathwada and Vidarbha worth Rs 313 crore across an area of over 300,000 hectares.
• While the weather forecast issued by the IMD on February 9 did mention that "thunderstorm accompanied with hailstorm very likely at isolated places" over Marathwada, the prediction was for February 12. It failed to make any such prediction for February 10 and 11.
• On March 4, 2018, IMD forecast thunderstorms and hailstorms at "isolated places" of North Madhya Maharashtra and Vidarbha on March 7 and 8. However, the bulletin issued at 1 PM was removed all the warnings of hailstorms and thunderstorms in Maharashtra.
• The weather body's string of missed monsoon forecasts began on June 11, 2021. IMD announced that the arrival of monsoon in Delhi, along with other parts of northwest India, had advanced by at least 12 days. Instead of its usual arrival date of June 27-28, monsoon showers would hit by June 15, the department said.
• The India Meteorological Department (IMD) had on June 17 predicted that "moderate rainfall and thunderstorms" will sweep through the Delhi city on the weekend as the monsoon hits the Capital, more than 10 days ahead of its usual onset date. But, as it turned out, residents spent the weekend sweating, with no rain anywhere in the city. The IMD's predictions, short- and long-term, have missed the mark on several occasions in 2021
• May 2021, Southwest monsoon seasonal (June to September) rainfall over the country as a whole is most likely to be normal (96 to 104 % of Long Period Average (LPA).

Why are weather forecasts sometimes wrong?

A tricky job: Predicting the monsoons in India is a notoriously difficult task. Since India falls in the tropical region, the changes in the weather conditions are more frequent than anywhere else in the world. With changing weather predictions, the parameters also frequently change, thereby affecting the forecast.

Impacts of inaccurate weather forecasts:

IMD bulletins are changing their forecast too fast for the farmers to respond. The farmers rely on IMD forecasts, even though they are not always accurate, but these sudden changes in advisories make it difficult for poor farmers to adapt to those changes. Moreover, their advisories and very generic, lacking district-level specifications, which do not help farmers in their preparedness.

The farmers need more accurate weather forecasts, and the meteorological department needs to be made accountable for making inaccurate forecasts. No one fixes responsibility to the IMD every time it goes wrong. It gradually erodes people's faith in the institution.

In India, where rain-fed farming dominates the agriculture sector and farmers sow seeds based on the IMD forecast, the institution's capacity to accurately forecast weather in a small geographical area needs to improve drastically and the weathermen should be held accountable for causing stress to farmers and people at large by providing an incorrect forecast.

The impact of monsoon on GDP is not that great as the share of agriculture in the GDP has fallen, but a bad monsoon has an inflationary impact. The wrong prediction of monsoon leads to volatility in the market and also increases hoarding.

The share of agriculture in the Gross Domestic Product (GDP) has fallen from 25 per cent in 1990-2000 to 15.7 per cent over the years. Still, in 2000-09, 60 per cent of the population relied on agriculture, and therefore on the monsoons, for a living. This also means that monsoon predictions play a huge role in what crops to sow and when.