Don’t blame El Nino, local conditions keeping rains at bay

As the month of June passes with a rainfall deficiency of around 40 per cent, a developing El Nino in the far-off Equatorial and East Pacific is increasingly being blamed as the culprit.

But this cannot be farther from the truth. If the monsoon has failed to deliver so far, it is because it has failed to get its basics right locally, according to Akhilesh Gupta, expert meteorologist and scientist.

Bay not switched on One is the refusal of the Bay of Bengal to ‘switch itself on’ and put out at least one low-pressure area in a week. Typically, a ‘low’ moves inland from the Bay in a west-northwest direction and meanders across the vast plains of Central and North-West with loads of moisture. The moisture, in turn, precipitates as rain. The slower the pace at which the ‘low’ moves, the greater its ability to keep the moisture supply lines on. This ensures enhanced precipitation over time and space.

But the Bay works to its own internal dynamics. There have been times when it has chosen to shut itself out for weeks on end during a monsoon, El Nino or not.

“So it is futile to fault the Pacific for what has been happening, or did not happen in the Bay thus far during the monsoon.”

No interaction The other major failure of the monsoon is its inability to interact with periodic western disturbances coming in from across the border. El Nino has hardly anything to do here either, Gupta says. Monsoon rain for North-West India is crucially dependent on east-to-west movement of ‘lows’ and west-to-east movement of the western disturbances.

Western disturbances have been moving in, but they have not obliged the monsoon with the typical ‘dip’ over North-West.

It is the dip that helps a disturbance to interact with monsoon lows. The disturbances have largely taken a much northward path cutting through Jammu and Kashmir and out of the country. The dip would take the disturbance southward over Rajasthan, Haryana, Delhi, Uttar Pradesh and Bihar.

Uttar Pradesh front Gupta said the monsoon can get most of things right if it manages to push into Uttar Pradesh in time. The rest North-West is covered through interaction with normal western disturbances.

“But so long as you don’t cover Uttar Pradesh, you have a problem. Which is what obtains even as June is about to end.”

Lastly, Gupta said the failure of land to heat up during April and May prevented the North-to-South pressure/temperature gradient from developing.

“What is monsoon? It is a massive sea breeze blowing in from the sea (relatively high-pressure area) to an area of low pressure formed over land due to intense heating.”

Unless the gradient develops to scale, this flow will be affected, Gupta said. “Extended winter and summer showers in North India interfered not only with the heating of the land but also the gradient.”

COMMENT NOW