1. Compiled By - Dr. Bheekam Singh
Indian Monsoon
Compiled By - Dr. Bheekam Singh
Part 2

2. Onset of Monsoon
&
Retreat of Monsoon

3. Onset of Monsoon Monsoon in India lasts for 100-120 days
From early June to mid September
Before entering into India monsoon winds encounters with many atmospheric conditions all the way
So these winds are pulsating in nature and not steady
So monsoon arrives with sudden down pour of rainfall continues to several days

4. Burst of Monsoon
This sudden onset of monsoon with heavy rainfall is known as ‘Burst of Monsoon’.

5. Arrives in India on 1st of june Kerala receives firs rainfall

6. South West monsoon reaching India
Divides in two parts at the start of peninsula
1. From Arabian sea side 2. BOB side

7. The Arabian sea branch reaches Mumbai around 10 days later , at Saurashtra and Kachach in mid of June and further to central parts of the country

8. BOB branch reach Assam on 1st week of June and after striking with mountains reflected to Ganga Plain

9. Both Branched merge at North Western Ganga Plain and provide rainfall there
Rainfall in Delhi in last June or precisely on 29th june is the gift of BOB branch

10. In first week of July reaches to Punjab, W
In first week of July reaches to Punjab, W. UP, Haryana nd Eastern Rajasthan

11. By mid July reach to Himachal and further north parts of India

12. Retreating of Monsoon Also known as ‘North east Monsoon’.
High Pressure starts to begin over north India
Wind moves towards south
Starts in early Sep
Retreat is more gradual than onset
Begins in northwestern states of India

13. Starts from north western states in September

14. Reaches north of the peninsula in Mid October
And windrow very fast in south parts of peninsula
Windrows completely in early Dec

15. Islands receives Monsoon rainfall from 1st of April to 1st week of May
Widrawal take place from 1st week of Dec to 1st week of Jan

16. Generally in eastern parts of peninsula
While retreating take moisture from Arabian sea and BOB and provides second round of rainfall called ‘Winter Monsoon’
Generally in eastern parts of peninsula

17. Break in Monsoon
During the south west Monsoon after having rains for several weeks the rain fails to occur for one or more weeks called ‘break in monsoon’.
These dry spells of monsoon are having different names and reasons in different regions:
In northern India fail if the rain bearing storms are not very frequent along the monsoon trough or ITCZ
Over the west coast they are associated with the flow of wind parallel to western ghats

18. Mango Shower
Towards the end of summer there are pre monsoon showers in Kerala and coast of Karnataka
Locally known as Minnesota
Help in ripening of mangoes

19. Blossom Shower
In late march or April there are showers in Kerala and near by areas
These showers helps in blossom of coffee flowers

20. Nor westers
Originate in the form of thunderstorms at Chota Nagpur region and flow towards north east
Provide rainfall in West Bengal and Assam
Their nature can be understand by the local name ‘Kalbaisakhi’ or calamity in the month if Baisakh
Useful for the cultivation of tea, rice and jute
Also called ‘Bardoli Cheerah’ in Assam

21. Western disturbances
“a low pressure area or a trough over surface or the upper-air in the westerly winds regime, north of 20°N, causing changes in pressure, wind pattern and temperature fields. It is accompanied by cloudiness, with or without precipitation.”
WDs originate in the Caspian Sea or the Mediterranean Sea as extra-tropical cyclones.
They gradually travel across the middle-east from Iran, Afghanistan and Pakistan to enter the Indian sub-continent.
Though WDs move across the Indian region throughout the year, they are in their peak during winter months of January and February. Their effect is minimal during the monsoon months in India.

22. over Northwest India including Punjab, Haryana, Uttar Pradesh and Delhi. Their effect sometime extends up to Gangetic plains and Northeast India.
They are also responsible for bringing snowfall in the higher reaches of Jammu & Kashmir, Himachal Pradesh and Uttarakhand.
Important for the development of Rabi Crops specially wheat