The typical onset date for the monsoon in Kerala is June 1. However, in 2025, the monsoon arrived on May 23, marking an early onset by 8 days. This was the earliest arrival since 2009, showcasing significant weather changes.
The India Meteorological Department (IMD) employs three crucial criteria to announce the monsoon onset:
The early onset of the monsoon in 2025 was attributed to several factors:
The MJO is a moving system of clouds and winds that circles the equator. Its presence over the Indian Ocean enhances rainfall conditions. For instance, in May 2025, the MJO was active, creating favourable conditions for the monsoon.
The Somali Jet is a significant wind current originating from the west, transporting moisture from the Arabian Sea to India. In May 2025, its activation was crucial in pushing moist air into the Indian mainland, facilitating the early onset of the monsoon.
Convection refers to the upward movement of warm, moist air that leads to cloud and rainfall formation. In 2025, robust convection over the Bay of Bengal and Arabian Sea stimulated cloud development, resulting in an earlier monsoon.
No, the timing of the onset does not guarantee sufficient rainfall throughout the season. Factors such as El Niño and the Indian Ocean Dipole influence total seasonal rainfall. For example, in 2015, although the monsoon arrived on time, it ended with a deficit due to El Niño.
Yes, although it's a rare occurrence. In 2022, both Kerala and the Northeast experienced monsoon onset simultaneously, largely due to coordinated moisture movement.
Q1. What factors affect the monsoon onset in Kerala?
Answer: Several factors influence the monsoon onset in Kerala, including wind patterns, rainfall distribution, and climatic phenomena like the MJO and Somali Jet.
Q2. How does the IMD monitor rainfall for monsoon declaration?
Answer: The IMD monitors rainfall by checking if at least 14 locations in Kerala receive a minimum of 2.5 mm of rain for two consecutive days as a condition for declaring the monsoon onset.
Q3. Why is the Somali Jet important for the monsoon?
Answer: The Somali Jet is crucial as it carries moisture-laden winds from the Arabian Sea towards India, significantly influencing the onset and intensity of the monsoon.
Q4. What is the significance of convection in monsoon patterns?
Answer: Convection is vital for monsoon patterns as it leads to the formation of clouds and precipitation. Strong convection can enhance rainfall, as observed in 2025.
Q5. Can early monsoon onset predict overall rainfall for the season?
Answer: No, early monsoon onset does not guarantee good seasonal rainfall. Other climatic factors also play a significant role in determining total rainfall.
Question 1: What is the typical onset date for the monsoon in Kerala?
A) May 23
B) June 1
C) June 15
D) May 15
Correct Answer: B
Question 2: Which department declares the onset of the monsoon in India?
A) Ministry of Weather
B) India Meteorological Department
C) Weather Forecasting Agency
D) National Weather Service
Correct Answer: B
Question 3: What is a prerequisite for the IMD to declare monsoon onset?
A) 20 mm rainfall
B) Wind from the east
C) Low-pressure system
D) 14 locations receiving 2.5 mm rainfall
Correct Answer: D
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