Why in News?

The southwest monsoon covered the entire country by June 29, nine days earlier than its usual date of July 8. This is only the tenth time since 1960 that the monsoon achieved nationwide coverage in June.

What’s in Today’s Article?

• Early Onset in Kerala Set the Pace
• Key Drivers of the Monsoon’s Rapid Advance
• Conclusion

Early Onset in Kerala Set the Pace

• The monsoon arrived in Kerala on May 24, eight days earlier than usual, driven by an active Madden-Julian Oscillation (MJO) phase in mid-May.
• This early onset laid the foundation for the monsoon’s rapid progress.
• Monsoon Progress: Mostly Ahead of Schedule
  • South, East, and Northeast India saw early arrival.
  • Northwest India was near normal.
  • Central India witnessed slight delays.

Key Drivers of the Monsoon’s Rapid Advance

• The southwest monsoon covered the entire country by June 29, nine days ahead of its normal schedule of July 8.
• This marks only the tenth instance since 1960 that nationwide monsoon coverage occurred in June.
• Low Pressure Systems
  • India experienced five low-pressure systems in June.
  • These act as moisture magnets, drawing in rain-bearing winds and accelerating monsoon movement inland.
• Active Madden-Julian Oscillation (MJO)
  • MJO is a moving system of clouds, rainfall, winds, and pressure near the equator that travels eastward.
  • When active near India, it enhances monsoon by increasing cloud cover and moisture, leading to stronger rainfall.
  • An active MJO phase significantly boosts monsoon onset and progression.
  • June continued to see an active MJO, enhancing cloud formation and pushing rainfall northwards, aiding monsoon spread.
• Favourable Monsoon Trough Position
  • The monsoon trough is an elongated low-pressure area extending from northwest India to the Bay of Bengal.
  • It plays a key role in determining rainfall distribution during the monsoon.
  • A favourable monsoon trough position, especially when it shifts south of its normal, helps draw in moisture-laden winds from the oceans, intensifying rainfall over central and northern India.
  • Its position influences the strength, spread, and duration of monsoon rains.
  • The monsoon trough remained south of its normal position, facilitating increased moisture inflow and early rainfall across regions.
• Neutral ENSO (El Niño-Southern Oscillation) Condition
  • ENSO is a climate pattern involving temperature fluctuations in the central and eastern tropical Pacific Ocean, with three phases: El Niño, La Niña, and Neutral.
  • A neutral ENSO phase means sea surface temperatures are close to average.
  • This phase neither suppresses nor excessively enhances rainfall, allowing the Indian monsoon to progress normally, supporting stable and widespread rainfall patterns.
  • ENSO was in a neutral phase, supporting normal monsoon rainfall.
• Neutral IOD (Indian Ocean Dipole) Conditions
  • An is a climate phenomenon marked by differences in sea surface temperatures between the western and eastern Indian Ocean.
  • It has positive, negative, and neutral phases.
  • A neutral IOD phase means there is little to no temperature difference between the two regions, resulting in minimal influence on the Indian monsoon.
  • This allows monsoon rainfall to be primarily driven by other favorable factors like MJO and ENSO.
  • This year, IOD also remained neutral, having minimal impact—neither enhancing nor suppressing rains.

Conclusion

This year’s monsoon has been marked by early onset, rapid progression, sudden pauses, and localised weather disasters. With much of the season still ahead, it remains uncertain whether the pattern will stabilise or intensify further.