Madden-Julian Oscillation

Madden-Julian Oscillation: Recently, Mumbai’s monsoon arrived two weeks early in 2025, causing heavy rain, waterlogging, traffic jams, and train delays, making it the wettest May in over 107 years.

o The Madden-Julian Oscillation has emerged as the key factor behind these unprecedented heavy rains.

• About Madden-Julian Oscillation : An ocean-atmosphere phenomenon that influences global weather patterns, causing significant fluctuations in tropical weather on weekly to monthly timescales.

o Characteristics: Represents a disturbance in clouds, wind, and pressure.

ü Moves eastward at 4-8 meters per second.

ü Completes a global circuit roughly every 30-60 days, sometimes taking up to 90 days.

ü Most prominent over the Indian and Pacific Oceans.

o Effect on Weather: As the MJO moves, it often divides the Earth into two halves:

ü One experiencing the active (enhanced rainfall or convective) phase.

ü The other in the suppressed rainfall phase.

o Impact on Indian Monsoon: The MJO cycle has eight phases.

ü When the MJO is over the Indian Ocean during monsoon season, it enhances rainfall over the Indian subcontinent.

ü If the MJO lingers longer over the Pacific Ocean, it tends to cause poor monsoon rainfall in India.