---
title: "Subtropical Westerly Jet Stream: UPSC Guide | Model Diplomat"
description: "The subtropical westerly jet stream is a crucial air current that influences seasonal weather patterns and the Indian monsoon, important for UPSC candidates."
url: "https://modeldiplomat.com/learn/glossary/subtropical-westerly-jet"
---

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Model Diplomat Research Team · Last reviewed June 22, 2026

TL;DR

- The subtropical westerly jet stream is a fast, high-altitude west-to-east air current centred around 30 degrees latitude that governs seasonal weather and the Indian monsoon.
- How does the subtropical westerly jet trigger the Indian monsoon?
- What is the difference between the subtropical and polar jet streams?
- Why does the subtropical jet split into two branches over India in winter?
- How is the subtropical westerly jet different from the tropical easterly jet?

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

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The India Meteorological Department in 2019 attributed the week-long delay in the southwest monsoon's onset over Kerala partly to the slow northward retreat of the subtropical westerly jet from the Indian plains.

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