The Anatomy of a Swell
Giant waves are not really that rare. All that is required is a sufficiently powerful ocean storm. And since oceans cover about 2/3 of the earth’s surface a number of such storms are bound to develop each year. Giant waves that are not just a formless mass of avalanching whitewater however, are exceptionally rare. In order for the waves to reach monstrous proportions while still maintaining surfable shape, a strong storm is only the first component in a series of crucial steps that must be meant.
Location is a key factor in this complex process. Giant waves that do not travel far enough away from their stormy origins will remain contorted by chaotic conditions Contours of the ocean floor become critical when a giant wave approaches the coast, as they control what the ultimate size and shape of the wave will be before it reaches shore. Finally it is the local wind at the wave’s destination that determines wave quality. A giant wave can be groomed to perfection by favorable flow or ripped to ruins by the wrong winds.
This anatomy of a swell details the step by step, storm by storm process that give rise to not just a giant rideable wave, but the giant rideable wave.
Local bathymetry can often be an overlooked feature when the average surfer is trying to grasp on a large swell. But in most cases when and where large epic surf goes down the ocean floor is where the magic happens. This is especially true when looking at the stretch of beach just north of Nazare, Portugal, given the fact that it is just basically just a sand bottom beach break with no underwater reef or point to focus the swell. Normally without some type of underwater dynamics, many swells,( especially the larger ones) would be hopelessly closed out.
The Nazare Canyon is the longest submarine canyon in Europe. It dissects the Iberian margin in an east – west direction, ranging from 50 meters deep at the continental shelf just offshore to roughly 5000 meters deep at the Iberian abyssal plain. Because Nazare is a sand bottom beach break, it requires a drastic, rapid change in ocean depth to help amplify swells in order to create such large, powerful surf. This is all possible due to the canyon just offshore. But the special thing about this canyon is that the headboard is less than a mile offshore. What this does is not only focus extra swell (especially the longer period) into the region, but it also allows swells to greatly increase in size very close to the coast.
Swells will refract from deep water towards the shallow water. Here is an example of a WNW – 300 degree swell with a longer swell period of 16 seconds. The swell will feel the offshore bathymetry of the ocean floor and wrap better into the coast. Various shallow spots offshore will also twist the swell direction in many areas a, creating crossed up peaky waves at some spots. We can also see why the deep water Nazare Canyon produces very large waves with the merging of extra swell energy out of deep water.
Because it is a beach break, these various shallow points offshore play a major factor in creating better-shaped waves with crossed up peaks instead of huge closeouts. This can also make for a very challenging and very dangerous proposition, especially when the waves get big.
Section 3: Storm/Fetch size
The perfect storm test/analysis is a unique one, given the fact that it wasn’t one specific storm that created this swell and record wave. There were actually three separate storms that had a hand in making this historic event possible. This scenario makes the storm/fetch size a combination of a series of low pressure systems over several days time. Therefore, by the time the third (and strongest of all) storm moved across the Atlantic, the two previous systems had created a very agitated sea state. What this does is allowed for an exceptionally large amount of energy to be transferred into the ocean, resulting in larger wave heights and stronger, more consistent surf.
The first two storm centers were part of a large complex low moved across the North Atlantic . At its peak, the fetch it developed stretched across 1,250 nautical miles of ocean with 30-40 foot seas. The third and final storm was an intense low that was the icing on the cake as it moved across the Atlantic. It also happened to be the largest and strongest in the series and covered even more area than the first two storms combined. At this storm’s peak, it stretched out over 1,320 nautical miles roughly half the width of the United States.
In terms of storm movement, there are two main areas of focus when determining if a storm has big wave potential.
- Fetch duration– The slower a storm moves the more energy can be transferred into the ocean.
- Storm track If the storm moves towards the particular area of interest it contributes to the overall wind speeds and has better potential for wave growth.
All three of these storms were classic mid latitude traveling cyclones. Individually their duration was nothing spectacular they each had a life cycle of around two to three days and moved rather quickly across the ocean. However the storms followed each other in rapid succession, which allowed them to be evaluated as one unit and determined there was a fetch of 30—40 foot seas and 35-to- 45 knot+ winds that lasted a full six days.
Each storm in this sequence took a favorable track through the Atlantic from west to east and, with the majority of strong winds in each system from the WNW; they created a very large sea state moving towards the Portuguese coast. The first two storms moved northward, and they eventually made landfall in the UK. The third final storm marched straight towards Portugal and eventually slammed into the country by midday . Thankfully that was after the record-breaking wave was already in the bag.
FETCH WIND SPEEDS: Wind speeds are extremely vital factor in significant swell events, as the stronger the winds, the larger the resulting surf (generally speaking). While this storm did not have the strongest winds possible, what it did have was a vast area of strong gale-to storm-force (47-63 mph) winds aimed directly at, and moving directly towards the Portuguese coast.
All three storms has very impressive wind speeds throughout the duration, consistently registering 35 to 45 plus knots. However, both the first and third storms whipped up a good chunk of 50-60 plus knot winds over a 23 to 24 hour period. The kicker was that these winds were also coming from the W to WNW and aimed directly at Portugal.
The third a d final storm originated from a large northeastern that formed early on. Along a cold front to the southeast. This storm hammered U.S eastern coast.
Another reason this storm had such a strong portion of intense winds as it moved into the Atlantic was a large plume of tropical moisture that was piled up in the Caribbean before the storm exited the east coast. The combination and collision of the cold air already within the storm and moist/tropical air being pulled up from the south really allowed this system to amplify and deepen.
The strong storm systems that produce these significant swell events are a mess of howling winds and large seas. The three storms that whipped up these swells were no different, with the final storm moving into the Portuguese coast with onshore winds and tattered conditions. Finding large surf in Europe was not the hard part, but catching the right spot at the right time for favorable conditions required timing, research, luck and major commitment—not to mention a flexible schedule and some cash. So, on the day of a giant wave, the Portugal coast was in between fronts with mainly clear skies and winds were light offshore from a southerly direction, ahead of the approaching cold front offshore. The local weather on that epic day was ideal. Conditions were the cherry on top for this event.
Simply put it was the very large, deep Nazare Canyon that really made the swell this large and the record-breaking wave even possible. Yes, the storm was very impressive and the conditions lined up just right for clean, huge surf but without the special features of this huge canyon, waves in excess 100 feet would not have been possible.
When waves measuring 100 feet plus are ridden and actually documented with video, it’s hard not to give this swell an A+ rating. However there were a couple of factors within this storm that did not leave a little room for improvement. The depth, size and location of the Nazare Canyon present the possibilities for even larger surf, given a stronger, larger storm.
See you at the beach!
- Garrett Mcnamara’s 100 foot wave at Nazare, Portugal (scsurfbutler.com)
- Fearless Surfer Conquers Epic 100-Foot Wave (wired.com)
- 100 Feet Tall Wave Largest Ever Surfed (ritholtz.com)