'Forecast is bound to have inherent errors'

Dr O P Singh, deputy director general of meteorology at Regional Meteorological Centre in Delhi, says it’s not a good idea to predict the weather too many days in advance. People would lose confidence in the department if the predictions don’t come true.

Excerpts from an interview with Avinash Singh Sudan:

Why are the predictions not accurate?

It’s a scientific challenge. We model the atmosphere which is an approximate model. There are six equations that define atmosphere.

These are known as primitive equations which are based on three physical laws — law of conservation of mass, law of conservation of momentum, and law of conservation of energy. They don’t have an exact or analytical solution due to which approximate predictions are obtained.

There is an initial error inherent in the modelling of atmosphere. With passage of time this initial error increases. The forecast is bound to have errors as it is a universal limitation of weather prediction science.

Why does the forecast keep changing for a given day?

The system can predict weather conditions for as many as 10 days from a given day. The next day, it will predict for 10 days ahead. In the process we get two predictions for a day.

For example, on Monday we will forecast for Tuesday and Wednesday. And on Tuesday we will again forecast for Wednesday, Thursday and so on. Therefore, we get two predictions for Wednesday. We take the latest forecast.  

What stops you from giving frequent warnings?

There is always a fear that if we keep giving warnings and they aren’t accurate, people will lose confidence in us. We are sure only two to three days in advance and then we issue a warning.

Therefore, a period of two to three days has become the convention. (But) we provide warnings for five days in advance for specific demands.

How can Regional Meteorological Centre in Delhi increase its efficiency?

A structure needs to be developed in which the roles of different departments like health, electricity and Met need to be interlinked. IMD (Indian Meteorological Department) caters to event and pilgrimages like Amarnath Yatra and provides warnings a week ahead.

So it is nothing new for us. Power consumption totally depends on the temperature and humidity.

Vector-borne disease can be controlled in Delhi if the Met dept gives correct information about rain.

We are ready to give such services but there should be a structure where health, electricity board and Met department should come together.