The Hindu Business Line : Monsoon may enter weak phase

All weather models are now unanimous in their assessment that the monsoon would go into a weak phase from June 8 with no scope for revival seen for at least next four to five days.

It's all over for the onset pulse bar, according to meteorologists. The next pulse could be around June 19 when the monsoon-friendly Madden-Julian Oscillation (MJO) wave is due next to stroll into the Indian Ocean region.

A periodic westerly wave travelling into the east, the MJO helps stimulate the moisture-laden Inter Tropical Convergence Zone (ITCZ) and drive rain into the mainland. Meanwhile, predictions made by the eight-member ensemble T-80 model for extended rainfall (monthly) run by the National Centre for Medium Range Weather Forecasting (NCMRWF) suggest that the country is heading for an overall rainfall deficit for the month of June.

Revealing this to Business Line, Dr Akhilesh Gupta of the NCMRWF said the forecast has been made on the basis of persisting and predicted sea surface temperature data made available by the Space Applications Centre (SAC), Ahmedabad.

The upper air cyclonic circulation over North Bay of Bengal is slowly descending to lower levels to become a low-pressure area but models suggest that it could die a premature death. It is already generating rain over parts of the east, and would have lost quite a bit of moisture by the time it slides fully down.

Model solutions

The resulting wet session has already covered parts of Orissa, Jharkhand, Chhattisgarh and West Bengal. The `low' is likely to get sheared off by prevailing westerlies over a period of the next 48 hours.

That will switch off the last active system influencing weather over the mainland, shutting out monsoon over the entire country, Dr Gupta said.

According to Mr Jim Andrews of AccuWeather, model solutions show persistent, if weak, upper trough having an axis over Afghanistan and western Pakistan for at least a week to come.

"This is not to say that rains are going to leave the subcontinent, but there is certainly going to be a backing off; breaks in rain will be more and longer along the west coast whereas, daily hit-or-miss showers and thunderstorms will hold sway over the southeastern one-half to two-thirds."

Farmers in the peninsular interior where the onset pulse was not able to penetrate had refrained from sowing. But those who did where the monsoon was declared as having arrived only to back off later, could witness withering away of the seeds, says Dr Gupta.

Up north, the untimely wet session ushered in parts of Bihar and East Uttar Pradesh by a prevailing western disturbance may have also raised a false alarm for farmers. Normal date of monsoon onset in these parts is around June 11 or 12, and the current spell has a clear pre-monsoon weather pattern about it.

Bajra crop

A similar situation obtains in Rajasthan where farmers take the first rain of the season, monsoon or not, as signal to sow Bajra. They do it in the belief that the next spell of rain would come within the next 15 days latest, a period which the newly sown Bajra crop is known to take in its stride.

But the fact is that the farmers could be way off the mark, since there's no way of knowing when monsoon rains would reach the northwest of the country. Any prediction on this could be made only after the system has covered the east in its entirety, unveiling the seasonal trough along the northwest-southeast corridor.

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