When swell patterns shift
Distinguish general seasonal climatology from live buoy telemetry when planning your sessions.
Wave period and compass angle dictate where to drive
Two forecasts reading "3 to 4 feet" can produce entirely different surf sessions depending on the dominant wave period (measured in seconds between crests) and the true compass angle of arrival. Short-period windswell (7 to 10 seconds) travels near the surface, bends poorly around headlands, and favors open beach breaks with peaky sandbars.
Long-period groundswell (15 to 20+ seconds) extends deep toward the continental shelf. As these deep-water orbital waves feel underwater canyons or headland points at depths of 50 to 80 feet, they bend (refract) toward shallow water, wrapping cleanly into sheltered bays while closing out straight, featureless beaches.
Seasonal comparison matrix
Use this quarterly reference table to anticipate dominant swell sources, typical morning wind patterns, and which coastal geometries perform most reliably.
| Season Window | Primary Swell Engine | Typical Compass & Period | Diurnal Wind Pattern | Most Suitable Break Types |
|---|---|---|---|---|
| Autumn Transition (Sep – Nov) |
Early Gulf of Alaska lows overlapping late Southern Hemisphere pulses | 280°–305° WNW (12–16s) & 190°–210° SSW (14–17s) | Light offshore land breezes at dawn; delayed afternoon thermal onset | Combo beach breaks, dual-exposure cobble points, and shallow reefs |
| Peak Winter (Dec – Feb) |
Deep North Pacific & North Atlantic extratropical storms | 270°–310° W/WNW (15–20s) | Variable frontal winds; clean offshore mornings between storm troughs | South-facing points, headland coves, and deep-channel reefs |
| Spring Upwelling (Mar – May) |
Subtropical high-pressure ridges & fading mid-latitude lows | 290°–320° NW (8–13s) with early 195° SSW forerunners | Fresh NW coastal gales by 11:00 AM; cold upwelling water temperatures | Northern wind-shadowed hooks, kelp-protected reefs, early dawn beach breaks |
| Summer South Window (Jun – Aug) |
Tasman Sea & South Pacific winter storms + Baja tropical systems | 175°–215° S/SSW (15–21s) & 160° SSE (11–14s) | Mild marine layer dawn patrol; gentle SW/W sea breeze by midday | South-facing cobblestone points, jetty wedges, and summer sandbars |
Island shadowing & headland refraction
Offshore islands and prominent capes act as natural gates. Knowing your break's open window prevents skunked drives.
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Channel Islands Blockage (Southern CA)
San Miguel, Santa Rosa, and San Clemente Islands cast sharp shadows across Santa Barbara, Ventura, and Orange County. A 295° WNW swell may light up San Diego while leaving North Orange County waist-high.
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Point Conception & Headland Wrap
Only swells with periods of 14 seconds or longer possess enough deep-water reach to wrap 60+ degrees around major headlands into sheltered south-facing bights.
External verification references
Always cross-check seasonal expectations against current marine telemetry before departing. These links are external references, not live readings hosted here.
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National Weather Service Marine Forecasts
External reference: Coastal waters synopses, small craft advisories, and nearshore wind timing predictions.
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Surfline / Historic Buoy Archives
External reference: Directional spectra plots separating primary groundswell trains from secondary windswell clutter.