During the Monsoon season, there are periods when the Monsoon trough shifts closer to the foothills of Himalayas, which leads to sharp decrease in rainfall over most parts of the country.
However, rainfall increase along the foothills of Himalayas, Northeast India and parts of the Southern Peninsula (Rayalseema and Tamil Nadu). Such a synoptic situation is known as the ‘break’ Monsoon period.
What are the striking features of the ‘break’ Monsoon period?
• Normally the Monsoon trough runs from Sri Ganganagar in Rajasthan to Kolkata. During break Monsoon, the trough shifts closer to the foothills of Himalayas or sometimes not visible at all.
• Middle of August is most prone to ‘breaks’ and that too longer breaks. Consequently, Northeast and parts of South India receive good showers while rest of the country remains mainly dry.
• Rainfall ceases over most parts of India. Heavy Monsoon showers are witnessed over/near the foothills Himalayas, but not over the entire length simultaneously.
• The Himalayan region to the east of 85°E receives heavy Monsoon showers. Accordingly, Sub Himalayan West Bengal, Sikkim, Assam and Arunachal Pradesh are more susceptible to heavier rainfall. Bihar, Jharkhand and West Bengal also receive above normal rainfall during this period.
• In the Peninsular India, Rayalseema and Tamil Nadu receives good thundershowers.
• The northern plains witness a drop in humidity levels, the surface winds start blowing from the northwest direction and rainfall reduces considerably.
• The Monsoon trough normally slopes southward with height because there is a drop in temperature. As Monsoon in India takes a break, the trough does not show any southward slope.
• The pressure gradient at surface levels over the Peninsular India weakens, while it becomes more over the Gangetic plains. Normally, the reverse happens during the four month-long Monsoon season.
Image credit- deccan chronicle