If lucky, Kerala may get rains from July second week

On Tuesday, Kerala could be clearly seen from space. The latest INSAT images show Kerala as a narrow lush-green bitter-gourd shaped strip on the southwestern tip of India. No view of Kerala could have been more disheartening.

Had it been a normal southwest monsoon, it should not have been possible to get such a clear view of Kerala from space. The view should ideally have been blocked by white cotton-like swirls that suggest clouds. Today, there is a profusion of thick cotton-like swirls over the entire stretch of Central India, from Gujarat in the West to West Bengal and Odisha in the East.

From above, the white puffy cloud formation over Central India looks like ice-cream over the dry inverted cone of South India.

Of course, some weak white patches had formed over the green bitter-gourd in the afternoon. But they were evidently not good enough for rains. The highest rainfall was recorded in Ottappalam in Palakkad, and that too a weak 6 cms. Already, the monsoon deficit is 48 per cent.

Waiting for chain service

It looks like the southwest monsoon has betrayed Kerala. “It is still early to say so. There will be rains but only a week later,” a top Meteorological Department official said. According to him, monsoon could be active over Kerala in the second week of July.

The monsoon cloud moves like a chain service. “Now the cloud band has propagated northwards and that is why there is strong rains in places like Surat and Mumbai,” said Manoj, a weather researcher in CUSAT, Kochi. “Once the formation dies out there, it will start once again from the southwest. Then, Kerala will hopefully get rains,” Manoj said.

This meteorological chain service of the clouds is called periodic oscillation. One oscillation, which is the movement of the monsoon cloud band from the southwest to the northeast, could last for 10 to 20 days. Once the oscillation dies down in the north and gets back to starting point, the monsoon trough or the off shore formation along the western coast will once again strengthen and cause the southwesterly winds to blow through Kerala.

“There is still a depression over the Bay of Bengal. (It is such a depression that pulls winds from the India Ocean towards the face of the Western Ghats and precipitates rainfall in Kerala.) This formation is unable to pull winds from the Indian Ocean and Arabian Sea because it is weaker than the atmospheric formation that has pulled the winds northwards,” the IMD official said. “The depression over the Bay of Bengal will hopefully come into play soon,” he added.

However, a couple of abnormalities of this year's monsoon has weathermen seriously worried. One, thunder and lightning have been frequently reported from various parts of the state this June. The southwest monsoon is largely free of lightning, unlike the northeast season.

Abnormal signs

This, weathermen say, is indicative of the intermittent nature of this year's monsoon. “Monsoon is not continuous this time, and that is why the frequent reporting of lightnings. The rains are highly localised. And nowhere in the state has it rained for more than half an hour at a stretch,” Manoj said.

Two, the wind has considerably slowed down. Usually, the wind speed during a monsoon touches 40-60 km per hour. IMD figures show that this time the speed has not crossed 30 km per hour. “This means that the rate of transfer of moisture from the Indian Ocean and Arabian Sea has fallen. Lower the speed, weaker the transfer of moisture,” the IMD official said.

It is the difference in pressure that causes wind movement from sea to land. Land heats up fast and when warm air rises cold air from the sea rushes in to take its place. “Now the sea too is warming up, affecting the speed of the winds,” Manoj said.

There are more ominous signs. The northeast monsoon towards the fag end of 2018 was deficient by 23 per cent. The summer showers during March-April and May were deficient by an alarming 55 per cent. And then, all of this leading up to a June deficiency of 35 per cent.