Question

The weather of which parts of India are influenced by western cyclonic disturbances?

Answer 1

Hint Western disruptions influence weather conditions during the winter season up to Patna (Bihar) and provide intermittent rainfall that is highly beneficial for standing rabi crops (wheat, barley, mustard, gram, lentil, etc.).

Complete Solution Step by Step
Western Disturbances –
1. In the winter season, the subtropical jet (STJ) is bifurcated into two branches due to the physical blocking of the Himalayas and the Tibetan Plateau.
2. One branch flows south of the Himalayas, while the second branch is situated north of the Tibetan Plateau.
3. The ridge of the jet stream produces anticyclonic conditions (with clockwise air circulation) over North-West India.
4. As a result, winds appear to descend over the north-western part of India, resulting in the creation of atmospheric equilibrium and dry conditions (anticyclonic condition= no rainfall).
But the subtropical jet (STJ) triggers occasional changes in general weather patterns.
5. The SubTropical Jets are pushing a temperate low pressure across the Mediterranean Sea to the east across Afghanistan, Pakistan, etc.
6. These storms are latent frontal cyclones, which pass at an altitude of 2000 meters from the mean sea level.
7. On average, 4 to 6 cyclonic waves enter north-western India every year between October and April.

Weather Associated with Wester Disturbances –
1. The arrival of these disturbances causes precipitation leading to a drastic drop in air temperature over Northwest India.
2. After the western disturbances move on, the weather becomes clear.
3. Western Disturbances also brings strong snowfall to the Himalayas and cold waves to the northern Indian plains.

Note:
1. Western disruptions affect the day-to-day weather of northwest India, especially during the winter season.
2. It is generally associated with cloudy skies, higher night temperatures, unusual rainfall, etc.
Around the Indo-Gangetic plateau, it carries cool waves and sometimes thick fog and cool day weather.