Killer thunderstorms and thunder squalls spawned by movement of weather-making western disturbances have left a trail of destruction over North India, claiming more than 100 lives from midnight on Wednesday.

Violent atmospheric events are not unusual over North India when heated up land (as in Rajasthan and neighbourhood) is accosted by humid winds from both the Arabian Sea to the South and Bay of Bengal to the far South-East.

Strong updrafts

While winds from the Arabian Sea are triggered by low-pressure waves of western disturbance, easterly winds from the Bay gets deflected by the Himalayas along the foothills into the plains of North-West India.

So, effectively, opposing winds have been rushing into each other over Rajasthan, creating strong and calamitous updrafts (strong vertical motion of winds) translating into dust storms, thunderstorms, thunder squalls, lightning and thundershowers.

This came about as a western disturbance travelled in from the Mediterranean across Central Asia, Iran, Afghanistan and Pakistan, and stationed itself over North Pakistan and adjoining Jammu & Kashmir on Thursday evening.

A successor disturbance is waiting at a perch over Iraq and Syria, and is expected to move in when the prevailing system moves further East from Jammu & Kashmir and across East and North-East India.

System may weaken

Global models have pointed to the existence of a low-pressure area straddling over the Indo-Pakistan border (South-West Rajasthan and adjoining Pakistan) buffeted by strong anti-clockwise flows on Thursday evening.

It could start weakening from Friday, but at the same time bring practically the whole of North, North-West, East and North-East India under the influence of trough of lower pressure.

This could mean that the region could be prone to thunderstorms and thundershowers though not as destructive as those witnessed from Wednesday midnight.

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