Tips to Better Understand Your Local Surf Forecast

There are a lot of surf fore­cast sites out there. Some are free. Some require sub­scrip­tions. Some come with fan­cy col­or-cod­ed charts. They all say pret­ty much the same thing based on the same hand­ful of mod­els. Still, if you are rel­a­tive­ly new to surf­ing and you don’t have a degree in mete­o­rol­o­gy, you might have a dif­fi­cult time under­stand­ing some of the more nuanced aspects of your local surf fore­cast. The fol­low­ing is a sim­ple guide designed to demys­ti­fy this information.

Wave Height
Tips to Better Understand Your Local Surf ForecastWhat should be the most impor­tant and most self-explana­to­ry ele­ment of your surf fore­cast page is actu­al­ly sub­ject to a long run­ning and heat­ed debate in the surf com­mu­ni­ty. How do we mea­sure wave height? The most accu­rate answer to that ques­tion is: how­ev­er we feel like it. Six foot in Hawaii is not the same as six foot in Cal­i­for­nia, which is not the same as six foot in Peru and is cer­tain­ly not the same as six foot in Flori­da. Some sites mea­sure in feet and oth­er sites use body mea­sure­ments (waist high, chest high, etc). 

What it is: Swell peri­od can be defined as the time between waves. Swell peri­od is typ­i­cal­ly mea­sured in sec­onds. So, a swell with a peri­od of 10 sec­onds would mean that, dur­ing sets, waves come every 10 sec­onds and there are ten sec­onds between break­ing waves. The peri­od for ride­able surf is gen­er­al­ly between sev­en and twen­ty-five seconds.

Why it’s impor­tant: Peri­od is just as impor­tant, if not more impor­tant than surf height. Peri­od is the sim­plest way to mea­sure a swell’s ener­gy. Put sim­ply, a swell with a large peri­od will have sig­nif­i­cant­ly more pow­er than a swell with a short­er peri­od. Many big-wave spots need a swell with a peri­od of six­teen sec­onds or more to even break. Alter­na­tive­ly, fea­ture­less beach­breaks with broad con­ti­nen­tal shelves are typ­i­cal­ly bet­ter on short­er peri­od swells and close out on long peri­od swells. The most impor­tant thing to under­stand with swell peri­od is that, at many spots, the peri­od will affect the size of the break­ing wave. This means that a swell read­ing 4ft at 18 sec­onds will be sig­nif­i­cant­ly larg­er than a swell read­ing 4ft at 8 sec­onds. Larg­er peri­ods will also fil­ter into more hard to reach places and rare spots will start to break.

DirectionWhat it is: Surf fore­cast sites often list swell direc­tion in one of two ways: com­pass bear­ings or degrees. In either case, the nota­tion sig­ni­fies the direc­tion from which the swell is com­ing, not the direc­tion it is going.  So, if you see a SSW swell, this means the swell is com­ing from the south-south­west. Like­wise (for the right-cast­ers), a NE swell is com­ing from the NE. Degree nota­tion works the same way, but is a bit more exact. Think of a com­pass as a 360-degree circle. 

Why it’s impor­tant: Depend­ing on your loca­tion, swell direc­tion is either mar­gin­al­ly impor­tant or extreme­ly impor­tant. If you surf a typ­i­cal east coast beach break with a huge swell win­dow, then swell direc­tion won’t have a huge affect. For exam­ple, at an east-fac­ing beach, a north swell will pro­duce more lefts, a south swell will pro­duce more rights, and an east swell will pro­duce either nice a‑frames or close­outs, depend­ing on bot­tom con­tour. How­ev­er, if you are lucky enough to live in an area with an abun­dance of reef­breaks and point­breaks, or you live in an area with off­shore islands, swell direc­tion is extreme­ly impor­tant. Off­shore islands may block or dis­tort incom­ing swells. Reefs and points are gen­er­al­ly fixed struc­tures so the shapes of the break­ing waves are direct­ly relat­ed to a vari­ety of fac­tors, includ­ing and espe­cial­ly swell direction. 

To best illus­trate this, let’s look at some of South­ern California’s most icon­ic waves: Mal­ibu, Rin­con, and Low­er Tres­tles. Here we have two rocky points and one rocky reef. These waves are fixed struc­tures with bot­toms that don’t move around too much. Rin­con is a win­ter wave that only breaks on swells from a Norther­ly or West­er­ly direc­tion. Why? The Chan­nel Islands block south swells from ever reach­ing the point. For many of the same rea­sons, Mal­ibu and Tres­tles are pre­dom­i­nant­ly “sum­mer waves.” Both the Bu and Tres­tles break best on South swells, and due to island shad­ow­ing, they often won’t break at all on a north swell. Mal­ibu is espe­cial­ly inter­est­ing because a seem­ing­ly insignif­i­cant degree shift can alter wave height by sev­er­al feet.  For this rea­son, it’s impor­tant to know which swell direc­tions work beat at dif­fer­ent par­tic­u­lar breaks, oth­er­wise you may see an over­head swell on the chart, pull up to your favorite beach, and find the ocean com­plete­ly flat. 

local-forecast-surfWhat it is: Cer­tain tele­vi­sion pun­dits may not be able to explain why the tide goes in and out, but mod­ern sci­ence has pret­ty much fig­ured it out. The grav­i­ta­tion­al pull of the moon caus­es tidal bulges on (high tides) on align­ing sides (sub­lu­nar and antipo­dal) of the earth and low tides along the equa­to­r­i­al mid­point of these two extremes.  Oth­er fac­tors like the sun and giant land­mass­es com­pli­cate things a bit fur­ther, but the pull of the moon pret­ty much sums it up. Some places have one high tide and one low tide a day (diur­nal) and oth­ers have two highs and two lows a day (semi-diur­nal). Most places fol­low a 24 hour and 50 minute tide cycle.

Why it’s impor­tant: Cer­tain spots are extreme­ly tide sen­si­tive. Some reefs are spec­tac­u­lar at high tide and dead­ly (or com­plete­ly exposed) at low tide. Oth­er reefs may be com­plete­ly under­wa­ter at high tide and only break on the low. If your area is prone to large tide swings, or your spot is espe­cial­ly tide sen­si­tive, you need to fol­low the tide chart to ever real­ly score. Most surf spots also get a small but mea­sur­able bump in surf size on an incom­ing tide.