01/07/2026
How Surfline’s Forecast Model Actually Works 🌊🛰️ Lead Forecaster Kevin Wallis breaks it down.
Ever wondered where Surfline’s swell forecast comes from? Here’s a simple breakdown.
Surfline’s LOTUS forecast model (often called a virtual buoy) separates the ocean into individual swell trains.
Each swell is traced back to its generation region—usually a storm or wind field that created it.
Because a single storm produces waves travelling in a similar direction but with different periods, the model groups all the energy from that same storm together.
It then calculates the significant wave height (the average height of the highest one-third of waves) and combines it with the dominant swell direction and period. That’s what becomes the primary swell shown in your local forecast.
Want to dive deeper? Check out the Swell Spectrograph in the Surfline app. It provides a visual breakdown of every swell contributing to the forecast.
You can also compare the forecast with data from nearby physical buoys listed at the bottom of the forecast page.
It won’t be a perfect apples-to-apples comparison, but it’s usually very close.
Comparing forecast data with real buoy observations helps you understand whether the model is running slightly high, slightly low, or right on the money.
The more you understand how the forecast is built, the better you’ll become at knowing when and where to surf. 🌊🤙 Surfline Surfline Australia Surfline New Zealand Surfline Europe
