Key Takeaways
- Wind causes the waves you surf; tides and tsunamis are waves too, from gravity and earthquakes. Wind speed, duration, and fetch set the size.
- Storm wind creates chaotic waves that sort by period over distance. Long-period energy crosses ocean basins; short-period energy dissipates through friction.
- Track distant storms to anticipate quality swell. North Pacific sends NW swells in winter; South Pacific sends SW swells in summer.
The Short Answer
Most ocean waves are caused by wind, including every wave you surf. NOAA lists two other causes: the gravitational pull of the Moon and Sun makes tides, which are extremely long waves, and earthquakes, landslides, or volcanic eruptions can set off tsunamis. Neither is surf.
Wind transfers energy to the ocean surface through friction. Three factors determine wave size: wind speed, wind duration (how long it blows), and fetch (the uninterrupted distance wind blows over open water). Stronger wind + longer duration + greater fetch = bigger waves. Once formed, waves organize into swells that travel thousands of miles across ocean basins — a North Pacific storm can send swell to Hawaii in 2-3 days and California in 4-5 days. NOAA's WaveWatch III models this entire process globally every 6 hours.
The Short Answer
Check it live
This guide is the why. The live page has today's swell, wind and tide.
Live regional forecasts →From Storm to Swell: The Formation Process
Inside a storm at sea, wind creates chaotic, short-period waves in all directions — called a "wind sea." As this energy radiates outward from the storm center, it undergoes dispersion: longer-period waves travel faster than shorter ones. Over hundreds or thousands of miles, the chaos sorts itself into organized bands of energy grouped by period — this is a swell.
Short-period energy (5-8 seconds) dissipates fastest through friction with the ocean surface. Long-period energy (12-20 seconds) loses very little and can cross entire ocean basins. A major Southern Ocean storm near Antarctica generates waves that arrive at California, Hawaii, and Japan as clean 16-18 second ground swell 7-10 days later. The fetch in the Southern Ocean is enormous — wind can blow uninterrupted for thousands of miles — which is why it produces the world's most powerful swells.
Storm wind creates chaotic waves that sort by period over distance. Long-period energy crosses ocean basins; short-period energy dissipates through friction.
What This Means for Your Session
Understanding wave formation helps you read forecasts: when you see a 16-second swell at 4 feet on Quiver, you know a powerful distant storm generated it days ago. That energy will be clean, organized, and powerful at your break. A 7-second swell at 4 feet means local wind right now — chaotic and weaker. Track storm systems on weather maps to anticipate swells 3-7 days out. Follow the North Pacific storm track in winter (produces NW swells for California) and South Pacific / Southern Ocean systems in summer (produces S-SW swells). Quiver's 7-day forecast shows these incoming swells so you can plan sessions around the best energy.
