---
title: "Madden-Julian Oscillation (MJO): Definition | Model Diplomat"
description: "The Madden-Julian Oscillation is a 30-60 day tropical disturbance that influences rainfall patterns, crucial for understanding the Indian monsoon."
url: "https://modeldiplomat.com/learn/glossary/madden-julian-oscillation"
---

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Model Diplomat Research Team · Last reviewed June 22, 2026

TL;DR

- The Madden-Julian Oscillation is an eastward-moving disturbance of cloud, rainfall, winds, and pressure that traverses the tropics over a 30-to-60-day cycle.
- How does the MJO affect the Indian monsoon?
- How is the MJO different from El Niño and the Indian Ocean Dipole?
- How do forecasters track the current MJO phase?
- Why does the MJO matter for sub-seasonal forecasting?

[Civil Service & Diplomatic Exams](https://modeldiplomat.com/learn/civil-services/glossary)Updated June 22, 2026

The Madden-Julian Oscillation is an eastward-moving disturbance of cloud, rainfall, winds, and pressure that traverses the tropics over a 30-to-60-day cycle.

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In the 2019 Indian monsoon season, the India Meteorological Department attributed the delayed onset and unusually wet September partly to the timing of Madden-Julian Oscillation phases over the Indian Ocean.

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