Storms come and go — it’s time to assess the unusual

Vibha Sharma in New Delhi

A series of thunderstorms and squalls left behind an unprecedented trail of destruction this month. More than 100 people, mostly in rural areas of Uttar Pradesh and Rajasthan, died in the dust storm whose speed exceeded more than 100 km per hour. Two Taj Mahal minarets are reportedly damaged. People in the north were left squirming with disbelief because such weather events are common in pre-monsoon period. But the Met warning came not only after the destruction but also several gaffes later. 

The meteorologists are baffled by the intensity of the storms so much so that the official forecaster, Indian Meteorological Department, and the Union home ministry misjudged their counter-moves. 

After the extraordinarily violent May-2 event, the Home Ministry issued a red alert for a second storm, which came and left with a whimper, making the agencies concerned a laughing stock.

Meteorologists, both from IMD and private forecaster Skymet say it was almost after a decade that they were witnessing such “startling” events, and also that it is not possible to provide exact prediction about intensity of weather systems having a short lifespan. “Such weather activity is common during this time of the season. But the intensity this year is a startling factor,” said Mahesh Palawat of Skymet.

An IMD official said the central forecaster had given alerts for the violent May 2 and May 13-14 events. The degree of intensity can only be judged about three hours before a storm, depending on the build-up. “We can issue alerts, but the time and intensity are variable factors in natural calamities such as dust storm and thunderstorm,” says the IMD official 

There are many reasons for an expected seasonal event turning into a “starling” eventuality. A confluence of factors has to be looked into. These factors include ‘unusual’ western disturbances (WD) and global warming/climate change. Adding to it are higher-than-normal temperatures and high-humidity in the region in the pre-monsoon summer. The WD is an extra-tropical storm originating in the Mediterranean region, bringing rain to the north-western parts of the country. It is a non-monsoonal precipitation pattern driven by Westerlies, moving from West to East. This year, however, they continued to affect lower latitudes even in May.

This year, when the “untimely” WDs struck, they encountered local factors such as high temperatures and already established troughs extending between far-west in Haryana to the far-east, carrying loads of moisture feed from the Bay of Bengal. The moisture supply and low-pressure troughs are welcome signs in summers, but together with “untimely” WDs and “unusually” high temperatures, they created violent thunderstorms. 

Adding to the cauldron was a vertical extant of clouds as high as 12-14 km. “A higher vertical extant of clouds leads to stronger storms. This year’s extant appeared after a decade. Climate change could be the reason. No study has, however, been done,” says Palawat.

High temperatures in adjoining Pakistan help in establishing a good monsoon. Pressure difference between the Arabian Sea and Pakistan regions is an essential factor for a good monsoon. But the hot region is now getting hotter. 

This year, pre-monsoon peak temperatures in some parts touched 50 degrees C, like last year. This is also said to be one of the reasons for added force of the westerlies, carrying desert dust into India.

Meanwhile, northwest plains and hills are also seeing temperatures higher than normal this year. As deforestation, forest degradation and haphazard urbanisation add to weather anomalies, it remains to be seen if 2018 monsoon season will be “normal” as predicted by the Met office.