Notwithstanding the unabated optimism of the India Meteorological Department (IMD) about normal monsoon this year, the progress of the south-west monsoon has been sluggish and patchy.
Not only is the total rainfall 11 per cent below normal but the advance of the monsoon towards the central and northern parts of the country is also behind schedule by a week to 10 days.
The deficiency so far is as high as 18 per cent in central India, where the monsoon arrived nearly a week behind schedule, and 22 per cent in the north-east, where it had set in almost on time before turning weak.
The south has had good monsoon rainfall, reckoned at 16 per cent above normal. Though the rainfall in the north-west is only 6 per cent below average, rainfall in this region is due to western disturbances and other factors unrelated to the monsoon, which is yet to arrive here.
| PROGRESS SO FAR Rainfall in different regions (% Departure from normal) | ||
| Region | Till June 17 | Till June 24 |
| North-west | 25 | -6 |
| Central India | -3 | -18 |
| South peninsula | 22 | 16 |
| North-east | -22 | -22 |
| All-India | -3 | -11 |
| Source: India Meteorological Department | ||
The distribution of rainfall is also uneven during the first three weeks of the 16-week monsoon season (June to September). The north-eastern region has witnessed a lull in the monsoon rainfall for about a week between June 10 and June 18. In the southern peninsula, though the monsoon arrived a day in advance on May 31, the rains intensified only after June 10. Central India had good rainfall between June 14 and 18, before the monsoon went weak.
The slightly early arrival of the monsoon in the Andaman Sea on May 17 (three days ahead of schedule) and in the Kerala coast on May 31 (one day in advance) was attributed by IMD to the formation of cyclone ‘Laila’ over the Bay of Bengal. It hastened the advance of the monsoon.
The post-onset hiatus of the monsoon, on the other hand, is being blamed on the cyclone storm ‘Phet’ over the Arabian Sea. This had delayed the advance of the monsoon to the west coast by a week, IMD sources point out.
Currently, the northern limit of the monsoon passes through Rajkot, Ahmedabad and Indore in the west-central region and through Daltonganj, Gaya, Muzzafarpur and Raxaul in the north-eastern region.
On the up side, IMD expects monsoon activity to pick up and cover some of the time lag as well. It foresees it to reach some parts of Uttar Pradesh, Uttarakhand and the western Himalayan region by the end of this month. The remaining parts of the north-west India, including Delhi, may be covered by the first week of July.
IMD’s confidence is reflected also in the updated long-range monsoon forecast issued on June 25. It projects the total rainfall to be 102 per cent of the long period average of 89 cms during the whole season. This forecast has the model error of ±4 per cent. Its first monsoon forecast issued on April 23 had put the likely rainfall at 98 per cent with the model error of ±5 per cent.
The updated forecast pitches rainfall in the north-west at 102 per cent, north-east at 103 per cent, central India at 99 per cent and south peninsula at 102 per cent. These figures are subject to a possible error of ±8 per cent.
Rainfall in the agriculturally crucial month of July has been predicted to be 98 per cent of the normal and in August about 101 per cent of normal. The model error in this case is ±9 per cent.
According to weather office sources, the upwards revision of the monsoon rainfall forecast is based on some positive developments which bode well for the monsoon. For one, the dreaded El Nino (warming up of the Pacific Ocean that generally subdues the monsoon), which had peaked in December, has dissipated.
In fact, it has given way to the emergence of La Nina (opposite of El Nino) which invariably has a salubrious influence on the monsoon. “There is very high probability (about 60 per cent) for the La Nina conditions to develop during the monsoon season which favours stronger than normal monsoon,” the IMD sources maintain.
Besides, the Madden-Julian Oscillation (MJO), which generally forebodes anomalous rainfall patterns, is anticipated to enter a better phase by moving away from the Indian Ocean in about a week. This is deemed good for the monsoon.
Moreover, the low-pressure area now hovering over the north-west Bay of Bengal may move north-westwards, resulting in enhanced rainfall in the east and central India in the next few days.
As a result, IMD today warned about heavy to very heavy rainfall in West Bengal, Sikkim, Arunachal Pradesh, Assam, Meghalaya, Nagaland, Manipur, Mizoram and Tripura in the next two days.
