How Wind Works
Wind is simply air moving from areas of high atmospheric pressure to areas of low pressure. The greater the difference in pressure, the stronger the wind. This fundamental principle drives everything from gentle sea breezes to powerful hurricanes. Understanding wind patterns helps you predict weather changes and make better outdoor plans.
Global Wind Patterns
The Jet Stream
The jet stream is a narrow band of strong winds flowing from west to east at altitudes of 30,000 to 40,000 feet. It acts as the boundary between cold polar air and warm tropical air. The polar jet stream is the most significant for US weather, typically flowing between 30N and 60N latitude.
When the jet stream dips southward, it pulls cold arctic air into the US, creating cold snaps and winter storms. When it pushes northward, warm air floods in, bringing heat waves. The jet stream also steers storm systems, which is why weather generally moves from west to east across the country.
Jet stream patterns can become "stuck" in certain configurations, leading to prolonged weather events like heat waves, droughts, or extended rainy periods. These persistent patterns, called blocking patterns, have become more common and are an active area of climate research.
Trade Winds
Trade winds are persistent easterly winds that blow in the tropics, between the equator and about 30 degrees latitude. In the Northern Hemisphere, they blow from the northeast; in the Southern Hemisphere, from the southeast. Trade winds drive tropical weather patterns and are crucial for the development and movement of hurricanes.
Hurricanes form and travel westward carried by the trade winds. As they move north, they eventually encounter the westerlies and curve back toward the east. This is why hurricane tracks often follow a parabolic path from the tropics toward the mid-latitudes.
Westerlies
The prevailing westerlies blow from west to east in the mid-latitudes (30-60 degrees). These are the dominant winds affecting the continental United States and Europe. The westerlies carry weather systems and storm fronts from the Pacific across the continent.
Local Wind Effects
Sea and Land Breezes
During the day, land heats up faster than water, creating a temperature difference that drives cool air from the ocean toward land — the sea breeze. At night, the process reverses as land cools faster than water, creating a land breeze that blows from shore out to sea. Sea breezes can moderate coastal temperatures by 10-20 degrees compared to inland areas.
Mountain and Valley Winds
During the day, mountain slopes heat up, causing air to rise along the slopes — an upslope or valley breeze. At night, cooling causes air to sink into valleys — a downslope or mountain breeze. These thermal winds can be quite strong in deep valleys and affect local weather significantly.
Chinook and Foehn Winds
When air is forced over a mountain range, it loses moisture on the windward side and warms as it descends on the leeward side. This can cause dramatic temperature increases. In Denver, Chinook winds can raise temperatures from below zero to 50F in a matter of hours. Similar winds in the Alps are called foehn winds.
Santa Ana Winds
The Santa Ana winds are hot, dry winds that blow from the interior deserts toward the coast of Southern California. These winds can raise temperatures dramatically, lower humidity to single digits, and create extreme wildfire danger. They typically occur from October through March.
Wind and Weather Forecasting
Understanding wind patterns can help you anticipate weather changes. Shifting winds often indicate an approaching front. Increasing winds may signal an approaching storm. On WeatherStream360, you can visualize real-time wind patterns on the interactive map, seeing both speed and direction animated across the globe.
Wind Speed Scales
The Beaufort Scale classifies wind from calm (0-1 mph) to hurricane force (74+ mph). The Enhanced Fujita Scale rates tornado intensity from EF0 (65-85 mph) to EF5 (200+ mph). The Saffir-Simpson Scale rates hurricanes from Category 1 (74-95 mph) to Category 5 (157+ mph). Understanding these scales helps you interpret weather forecasts and warnings.