Westerlies: Why the U.S. Feels Them More Than Europe

Contrary to a common misconception, the prevailing westerlies—the dominant mid-latitude winds blowing west-to-east—affect the United States more directly and intensely than Europe. Here's why.

Latitude Positioning

• Contiguous U.S.: Entirely within 24°N–49°N—the core westerlies belt (30°–60°N). Every state experiences westerly-driven weather systems.
• Europe: Spans 36°N–71°N. Only southern/central Europe (Mediterranean to Baltic) sits squarely in the westerlies. Scandinavia and Russia extend into the polar easterlies zone, weakening average westerly influence.

Mechanism: Coriolis & Pressure Gradients

Westerlies arise from the Coriolis deflection of air moving poleward from the subtropical highs. Maximum Coriolis effect at mid-latitudes creates the strongest zonal (west-east) flow—directly over the U.S. heartland.

Climate Impacts: United States

• Pacific moisture transport: Westerlies carry maritime air inland, creating the West Coast's wet winters and feeding Sierra/Cascades snowpack.
• Rain shadow deserts: Same winds descending Rockies create Great Basin and Mojave deserts.
• Jet stream coupling: Polar jet stream (westerly core) steers storms, creates severe weather outbreaks, and modulates drought/flood cycles.
• Temperature moderation: Maritime air prevents extreme continental cold in winter (except during polar vortex disruptions).

Climate Impacts: Europe

• Atlantic maritime influence: Westerlies bring mild, moist air—why London (51°N) is warmer than Calgary (51°N).
• North Atlantic Drift synergy: Winds drive the warm current extension, amplifying maritime effect.
• Storm tracks: European windstorms (e.g., 1987 Great Storm, 1999 Lothar) are westerly-driven extratropical cyclones.

Key Difference

The U.S. experiences the full continental expression of westerlies: moisture uptake, orographic lift, rain shadow, and re-intensification downstream. Europe experiences primarily the oceanic approach—moisture-laden but lacking the downstream continental transformation. The Rocky Mountains are the westerlies' great modulator; Europe has no equivalent barrier.