How To Forecast The Surf – Lesson Two: Wind

As we mentioned in our first surf forecasting lesson, the most important factor in predicting the surf is knowing when waves will arrive. While wind, weather, and tide conditions influence the quality of surf, they don’t matter much if the waves are flat. Let’s take a quick look at the updated forecast for Tuesday, January 11, 2011, to see how our original swell profile is holding up.

Above is the 50-hour Wavewatch III forecast of tomorrow’s swell, which has evolved from the 102-hour forecast to display two distinct, overlapping components. While our swell profile is consistent with the previous forecast, the presence of two swells in the water could result in jumbled conditions as the second swell fills Tuesday afternoon.

Without the individual swell components provided by the Wavewatch III model, these swell subtleties might simply be written off as “weird” or “funky.” However, knowing that a secondary (or tertiary) swell is in the water provides insight into why the peak is shifting, or certain waves are doubling-up. This level of detail is simply not provided by a general 8-10 foot forecast that leaves you scratching your head.

Lesson Two: Wind

Given a favorable swell profile, the second most important factor in forecasting the surf is wind. Wind conditions can produce beautiful, perfectly groomed lines, or completely tatter and ruin an otherwise epic swell. While some new-school aerialists may claim onshore as the new offshore, we’re not buying it. Who sits in the lineup and wishes the wind was “a bit more onshore?” No one.

There are a number of wind forecasts available online, and many draw their data from the same forecast models. We recommend Wind Guru (which also uses the Wavewatch III model), although you may have your own personal preference. Wind Guru does not provide data for Waimea Bay, so we’ll be referencing their Sunset Beach forecast. Ideally you’ll want to select the location that is nearest your intended surf spot, although an exact match may not be available.

Above is the wind forecast (as of 2:00 a.m. January 10th, 2011 HST) for Tuesday, which reveals light winds slowly clocking East throughout the day. According to this forecast, light onshore conditions will prevail in the morning, improving to side-offshore conditions by evening. Stronger gusts build overnight, with Southerly winds (turning a touch SSW) by Wednesday afternoon.

Based on the current swell profile for Tuesday, which predicts an afternoon peak, it appears as if the winds may clock around in time to produce fair to good conditions by the evening. Given the light a.m. wind speed, the morning session could see fair conditions, although the Northwest wind direction is unfavorable for the North Shore. Also, consistent North-Northwest winds through tonight may produce residual surface chop and accompanying morning sickness, making the Tuesday dawn patrol a bit of a gamble.

The official call for tomorrow: Sketchy winds and an 11-second swell period make the dawn patrol a roll of the dice, but worth a look if you’re already on the North Shore. It’s not worth calling in sick, but the winds are forecast to improve throughout the day, so check the cams at lunch to see if you should wiggle out of work a bit early. Fifteen-second Northwest fills in the afternoon, and could provide funky, combo-swell conditions at select spots.

As the swell begins to arrive tonight, stay tuned to both the Northwest Hawaii (@buoy51101) and Waimea Bay (@buoy51201) buoys for real-time wave observations. We’ll be reviewing these reports in our third surf forecasting lesson.

Additional Resources: Wind Guru