Assam, Meghalaya, Sikkim to see heavy monsoon rain, Delhi to be cloudy on Tuesday
The IMD has warned of extremely heavy rain of more than 20 cm over Assam, Meghalaya and Sub-Himalayan West Bengal and Sikkim on August 4, driven by five interacting weather systems. Here is what the science says, and whether Delhi and the northern plains will turn wet too.
India's heaviest rain on Tuesday, August 4, will not fall on its big cities. It will pour over the hills of the northeast.
Over Meghalaya and the foothills of Sikkim, the clouds are about to do something the India Meteorological Department (IMD) marks in its heaviest ink. They are forecast to drop more than 20 cm of rain in a single day.
The IMD calls this extremely heavy rainfall, the top rung of its rainfall ladder, meaning anything above 204.4 mm (20.44 cm) in 24 hours.
On August 4, it is likely at isolated spots over Assam, Meghalaya, and Sub-Himalayan West Bengal and Sikkim.
WHY WILL IT RAIN SO HEAVILY ON TUESDAY, AUGUST 4?
Blame a traffic jam of weather systems. Five of them are crowding the map.
The first is the monsoon trough, a long belt of low air pressure stretching across northern India. Picture a valley in the air. Winds slide in from either side, collide, and have nowhere to go but up, and rising damp air is simply rain waiting to happen.
Around it sit three cyclonic circulations, over northeast Rajasthan, over Sub-Himalayan West Bengal, and over northeast Assam. A cyclonic circulation is a slow spin of winds around a low-pressure centre that keeps lifting moist air off the land.
There is one more reason: the hills, not the plains, take the worst of it. When this soggy air is shoved against the steep slopes of the eastern Himalayas, it has only one way to travel, upward. As it climbs, it cools, and cool air cannot hold as much water, so the moisture wrings out as rain. Scientists call this orographic lift.
WHAT IS A WESTERN DISTURBANCE?
The fifth system is the newcomer. A western disturbance is a rain-bearing storm born far away over the Mediterranean Sea, which rides high-altitude winds eastward until it bumps into the Himalayas. On August 4, the system sits over the Jammu region.
It lives high in the troposphere, the lowest layer of the atmosphere and the thin skin where all our weather happens. When a western disturbance meets the monsoon, the rain over the northern hills tends to grow heavier.
WILL IT RAIN IN DELHI ON AUGUST 4?
Yes, gently. The IMD expects a generally cloudy sky, light rain through the morning, and another spell at night.
The maximum temperature should settle between 31 and 33 degrees Celsius and the minimum between 23 and 25, both below normal. A grey, damp, easy Tuesday.
WHERE IS THE FLOOD RISK HIGHEST?
In the hills. The IMD has placed Sub-Himalayan West Bengal and Sikkim under a moderate to high flash flood risk, the sharpest on its map, covering Darjeeling, Jalpaiguri, Cooch Behar and the Sikkim districts.
Arunachal Pradesh, Assam, Meghalaya and Uttarakhand carry a lower risk.
The Andaman and Nicobar Islands, meanwhile, face a thundersquall, a sudden and violent burst of wind gusting up to 70 kmph.
The monsoon, in short, is wide awake. For once, it is the mountains, not the metros, that will bear the brunt.
India's heaviest rain on Tuesday, August 4, will not fall on its big cities. It will pour over the hills of the northeast.
Over Meghalaya and the foothills of Sikkim, the clouds are about to do something the India Meteorological Department (IMD) marks in its heaviest ink. They are forecast to drop more than 20 cm of rain in a single day.
The IMD calls this extremely heavy rainfall, the top rung of its rainfall ladder, meaning anything above 204.4 mm (20.44 cm) in 24 hours.
On August 4, it is likely at isolated spots over Assam, Meghalaya, and Sub-Himalayan West Bengal and Sikkim.
WHY WILL IT RAIN SO HEAVILY ON TUESDAY, AUGUST 4?
Blame a traffic jam of weather systems. Five of them are crowding the map.
The first is the monsoon trough, a long belt of low air pressure stretching across northern India. Picture a valley in the air. Winds slide in from either side, collide, and have nowhere to go but up, and rising damp air is simply rain waiting to happen.
Around it sit three cyclonic circulations, over northeast Rajasthan, over Sub-Himalayan West Bengal, and over northeast Assam. A cyclonic circulation is a slow spin of winds around a low-pressure centre that keeps lifting moist air off the land.
There is one more reason: the hills, not the plains, take the worst of it. When this soggy air is shoved against the steep slopes of the eastern Himalayas, it has only one way to travel, upward. As it climbs, it cools, and cool air cannot hold as much water, so the moisture wrings out as rain. Scientists call this orographic lift.
WHAT IS A WESTERN DISTURBANCE?
The fifth system is the newcomer. A western disturbance is a rain-bearing storm born far away over the Mediterranean Sea, which rides high-altitude winds eastward until it bumps into the Himalayas. On August 4, the system sits over the Jammu region.
It lives high in the troposphere, the lowest layer of the atmosphere and the thin skin where all our weather happens. When a western disturbance meets the monsoon, the rain over the northern hills tends to grow heavier.
WILL IT RAIN IN DELHI ON AUGUST 4?
Yes, gently. The IMD expects a generally cloudy sky, light rain through the morning, and another spell at night.
The maximum temperature should settle between 31 and 33 degrees Celsius and the minimum between 23 and 25, both below normal. A grey, damp, easy Tuesday.
WHERE IS THE FLOOD RISK HIGHEST?
In the hills. The IMD has placed Sub-Himalayan West Bengal and Sikkim under a moderate to high flash flood risk, the sharpest on its map, covering Darjeeling, Jalpaiguri, Cooch Behar and the Sikkim districts.
Arunachal Pradesh, Assam, Meghalaya and Uttarakhand carry a lower risk.
The Andaman and Nicobar Islands, meanwhile, face a thundersquall, a sudden and violent burst of wind gusting up to 70 kmph.
The monsoon, in short, is wide awake. For once, it is the mountains, not the metros, that will bear the brunt.
India's heaviest rain on Tuesday, August 4, will not fall on its big cities. It will pour over the hills of the northeast.
Over Meghalaya and the foothills of Sikkim, the clouds are about to do something the India Meteorological Department (IMD) marks in its heaviest ink. They are forecast to drop more than 20 cm of rain in a single day.
The IMD calls this extremely heavy rainfall, the top rung of its rainfall ladder, meaning anything above 204.4 mm (20.44 cm) in 24 hours.
On August 4, it is likely at isolated spots over Assam, Meghalaya, and Sub-Himalayan West Bengal and Sikkim.
WHY WILL IT RAIN SO HEAVILY ON TUESDAY, AUGUST 4?
Blame a traffic jam of weather systems. Five of them are crowding the map.
The first is the monsoon trough, a long belt of low air pressure stretching across northern India. Picture a valley in the air. Winds slide in from either side, collide, and have nowhere to go but up, and rising damp air is simply rain waiting to happen.
Around it sit three cyclonic circulations, over northeast Rajasthan, over Sub-Himalayan West Bengal, and over northeast Assam. A cyclonic circulation is a slow spin of winds around a low-pressure centre that keeps lifting moist air off the land.
There is one more reason: the hills, not the plains, take the worst of it. When this soggy air is shoved against the steep slopes of the eastern Himalayas, it has only one way to travel, upward. As it climbs, it cools, and cool air cannot hold as much water, so the moisture wrings out as rain. Scientists call this orographic lift.
WHAT IS A WESTERN DISTURBANCE?
The fifth system is the newcomer. A western disturbance is a rain-bearing storm born far away over the Mediterranean Sea, which rides high-altitude winds eastward until it bumps into the Himalayas. On August 4, the system sits over the Jammu region.
It lives high in the troposphere, the lowest layer of the atmosphere and the thin skin where all our weather happens. When a western disturbance meets the monsoon, the rain over the northern hills tends to grow heavier.
WILL IT RAIN IN DELHI ON AUGUST 4?
Yes, gently. The IMD expects a generally cloudy sky, light rain through the morning, and another spell at night.
The maximum temperature should settle between 31 and 33 degrees Celsius and the minimum between 23 and 25, both below normal. A grey, damp, easy Tuesday.
WHERE IS THE FLOOD RISK HIGHEST?
In the hills. The IMD has placed Sub-Himalayan West Bengal and Sikkim under a moderate to high flash flood risk, the sharpest on its map, covering Darjeeling, Jalpaiguri, Cooch Behar and the Sikkim districts.
Arunachal Pradesh, Assam, Meghalaya and Uttarakhand carry a lower risk.
The Andaman and Nicobar Islands, meanwhile, face a thundersquall, a sudden and violent burst of wind gusting up to 70 kmph.
The monsoon, in short, is wide awake. For once, it is the mountains, not the metros, that will bear the brunt.
