Reading a surf forecast is an essential skill that separates good surfers from great ones. Understanding what makes waves work will help you score the best sessions and avoid frustrating flat days. Here's everything you need to know.
Swell - The Foundation
Swell is the energy that creates waves. Understanding swell is understanding surfing conditions.
Swell Height: Measured in feet or meters, this tells you how big the waves will be. But swell height doesn't equal wave face height - a 3ft swell might produce 4-5ft wave faces depending on other factors.
Swell Period: The time between waves, measured in seconds. This is arguably more important than height.
- 6-8 seconds: Wind swell, weak and mushy
- 10-12 seconds: Medium quality, decent power
- 14+ seconds: Groundswell, powerful and clean
A 4ft swell at 15 seconds will produce better waves than a 6ft swell at 8 seconds.
Swell Direction: Where the swell is coming from. Different breaks need different swell directions. Uluwatu loves SW swells, while Sanur needs SE swells. Know your spot's optimal direction.
Wind - The Make or Break
Wind can make perfect swell look terrible, or clean up messy conditions.
Offshore: Wind blowing from land to sea. Holds waves up, creates clean faces. The holy grail.
Onshore: Wind blowing from sea to land. Destroys wave shape, creates choppy, bumpy conditions.
Cross-shore: Blowing parallel to the beach. Can be surfable depending on direction.
Glass: No wind at all. Dawn patrol conditions. Often the best time to surf.
Wind Speed: Light winds (under 10 knots) are manageable even if not perfectly offshore. Strong winds (20+ knots) will ruin most sessions regardless of direction.
Tides - The Timing
Tides affect every wave differently. Knowing your break's optimal tide is crucial.
Low Tide: Waves break in shallower water. Often more hollow but can be too shallow on some reefs.
High Tide: Waves break in deeper water. Often fuller and easier but can lose shape at some spots.
Mid Tide: Often the sweet spot for many breaks.
Pushing/Dropping: The period as tide changes. Many breaks have a 'pushing' or 'dropping' preference.
Putting It All Together
The perfect forecast looks like:
- Solid swell (4-6ft)
- Long period (12+ seconds)
- Optimal swell direction for your break
- Light offshore or glassy conditions
- Favorable tide
Recommended Forecast Tools
- Surfline: Industry standard, paid subscription
- Magic Seaweed: Free option with good data
- Windy.com: Great for wind visualization
- Tide apps: Many free options available
Pro Tips
- Check forecasts 3-5 days out for trip planning
- Double-check wind forecasts morning of - they change
- Learn your local spots' quirks through experience
- When in doubt, go check it - forecasts aren't perfect
- Dawn and dusk often have the lightest winds
