Reading Swell Charts

Buoy charts show wave conditions over time, helping you identify trends, predict arrivals, and plan your surf sessions. Here's how to read them effectively.

Understanding Time Series Charts

Most buoy platforms (including BuoyBoy) display data as time series charts showing measurements over hours or days.

• X-axis: Time (hours or days)
• Y-axis: Measurement value (wave height, period, etc.)
• Trend lines: Show how conditions are changing

Reading Wave Height Charts

The wave height chart is typically your starting point:

Rising trend: Swell is building - conditions improving Peak plateau: Swell is maxing out - prime time window Falling trend: Swell is dropping - conditions declining Flat line: No swell activity

Pro tip: Look for the "sweet spot" where height peaks and period is longest.

Interpreting Period Charts

The period chart reveals swell quality:

• Indicates groundswell from distant storms
• Usually associated with powerful, well-organized waves
• Best surf conditions

• Wind swell or local storm activity
• Choppier, less organized waves
• May still be surfable but lower quality

• Multiple swells in the water
• Can create complex wave patterns
• Check direction to understand which swell dominates

Direction Charts

Direction charts help you understand:

Consistent direction: Clean, organized swell from one source Changing direction: Swell is shifting or multiple swells present Matching your break: Compare to your spot's optimal swell window

Example: If your break works best on 270-300° (west to northwest) and the chart shows waves steady at 285°, you're in the sweet spot.

Multi-Day Analysis

Looking at 3-5 day charts helps you:

1. Identify swell events: Distinct peaks in height and period 2. Predict timing: See when swells arrive and depart 3. Plan sessions: Target the peak of favorable swells 4. Compare buoys: Offshore buoys show swells before nearshore

Common Patterns

• Period increases first (swell is approaching)
• Height builds gradually
• Both peak together
• Period stays elevated as height drops

• Choppy, erratic height changes
• Periods stay low (6-9 seconds)
• Often correlates with local wind events

• Multiple period peaks visible
• Height shows combined energy from different swells
• Check spectral data to separate components (advanced)

Using Multiple Metrics Together

The best forecasting combines all three measurements:

• Height: 4-6ft (rising or steady)
• Period: 13-16 seconds (elevated)
• Direction: 280° (favorable for your break)

• Height: 2ft (falling)
• Period: 7 seconds (wind swell)
• Direction: 190° (blocked by headland)

Real-World Tips

1. Check multiple buoys: Offshore buoys predict, nearshore buoys confirm 2. Watch the trend: A rising 3ft swell may become 6ft in hours 3. Consider local factors: Bathymetry, reefs, and coastline shape affect how swells break 4. Combine with wind forecast: Offshore winds clean up the surf surface

With practice, you'll quickly spot good conditions and plan sessions with confidence.