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- India usually gets thunderstorms accompanied by rainfall, dust and hail in Jan, Feb and March months due to W.D.
- But this year they have continued even in April and May 2020
- According to IMD, there were 354 heavy rainfall events (absolute rainfall above 64.5 mm) across India in March and April.
- IMD Warning maps
Prediction for a Hot summer
- IMD had predicted warmer-than-usual weather for the months of March and April for India.
- It said average maximum temperatures were likely to be warmer-than-usual by 0.5-1°C for April, May and June in its latest seasonal outlook for temperatures on April 1.
- But temperatures were below normal in large parts of the country for March, April and now May.
- Temperatures were lower by 4-7 degrees Celsius (°C), in parts of Uttar Pradesh, Bihar and Jharkhand.
- There were no heat waves recorded in the country through May 13.
Thunderstorm cooling the temperature
- The heavy rain and storms led to cooler-than-normal temperatures across north, central and east India
- The maximum temperatures recorded by IMD were below normal in large parts of north, east, central and southern parts of the country according to the latest data available.
Western disturbances
- The main reason for storms, rainfall and cooler temperatures were western disturbances
- They are very difficult to predict.
- WD is an extratropical storm originating in the Mediterranean region that brings sudden winter rain to the north-western parts of the Indian sub-continent.
- It is a non-monsoonal precipitation pattern driven by the westerlies.
- Extratropical storms are a global phenomenon with moisture usually carried in the upper atmosphere, unlike their tropical counterparts where the moisture is carried in the lower atmosphere.
- In the case of the Indian subcontinent, moisture is sometimes shed as rain when the storm system encounters the Himalayas.
Why are WD more this year?
- Frequent western disturbances could be the result of
Unusually warm temperature over Eurasia
- The warm-cool pattern over the Atlantic Ocean working together to favour these western disturbances during the pre-monsoon
- Atlantic Multi-decadal Oscillation — a natural pattern of warm and cool phases in North Atlantic sea-surface temperatures Isn’t a cooler summer good for us?
- Warming of land surface in the summer, especially in the northern part of the country, is essential for attracting monsoon winds that occur due to temperature contrasts between land and ocean.
- The coming south-west monsoon may, thus, be weakened as a result of a cooler-than-normal north and central India during the pre-monsoon period.
Rising global average temperature
- The global average land and ocean surface temperature for March stood at 1.6 °C, above the 20th century average of 12.7 °C, according to the US National Centers for Environmental Information
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