Not possible to micro forecast thunderstorms in June, say experts

Delhi has seen a few instances over the last few days where the India Meteorological Department's (IMD) forecasts were way off the mark.

The primary of those being the weather forecast issued on Monday.

On Sunday, the IMD had only forecast a "thundery development" for the city on Monday.

By the time the Met office issued an "orange" alert, a fierce thunderstorm, packing winds of up to 100 kilometres per hour had already hit the capital.

Two people were killed and several injured as the storm uprooted hundreds of trees, disrupting road and air traffic and damaging vehicles and buildings, including the iconic Jama Masjid.

The city witnessed a partly cloudy sky on Wednesday, while the weather department had predicted a "thundery development".

Mahesh Palawat, vice-president (climate change and meteorology), Skymet Weather, said pre-monsoon activity in tropical and sub-tropical regions is a sudden development due to high temperatures and humidity.

"High temperatures and high humidity create thunderclouds that are capable of producing short, intense spells of rain and thunderstorms. These patchy clouds have a short diameter of 25-50 kilometres and they keep on moving. So it is difficult to give a micro forecast in terms of exact location and intensity," Palawat said.

Such events are not associated with a pre-defined or prominent weather system such as a low-pressure area or a depression that could help weather forecasters predict the area of impact with "good probability", he added.

Weather forecasting agencies spot such clouds with the help of doppler radars only when they start building up.

Thunderclouds appear along the trough, which itself keeps on oscillating. It does not remain fixed at a particular place. Even if it moves a latitude up or down, it means a difference of around 94 to 100 kilometres, Palawat said.

There is a greater chance of a sudden development of thunderstorms in May and June due to high temperatures and high humidity. Such developments cannot be predicted a day or two in advance, an IMD official said.