Breaking news: El Niño causing a swell time

Photograph by NOAA National Weather Service National Hurricane Center

Hurricanes Kilo, Ignacio and Jimena surround Hawaii
Photograph by NOAA National Weather Service National Hurricane Center

Spot the archipelago surrounded by three category 4 hurricanes last August. Right in the middle you can find the not-so-idyllic-after-all, Hawaiian Islands. I was stuck on the Big Island at the time, and instead of discovering tropical wonders, I found myself discussing with my neighbours whether or not to stock up on groceries – just in case. Whilst the extreme weather ruined the sunny bounty beaches I had envisioned, a few others could not have been more ecstatic. The surfer community, with nerves of steel, were preparing for the enormous waves to come. It has been suggested that the extreme weather is a result of the current powerful El Niño. While most news coverage on El Niño focuses on the negative effects, here I’d rather like to take the opportunity to look at how it creates paradise for the daredevil surfers, and plays a role in creating incredible waves like this:

Taylor Knox riding a 16-metre wave in 1998.
Video by Encyclopedia of Surfing, CC-video from Vimeo

The video above is American surfer Taylor Knox, riding a 16 metre wave in 1998. That year, El Niño’s condition was one of the most intense on record. Surf events across the Pacific featured some of the largest waves ever ridden. Let’s have a look at the mechanisms that drive these killer waves during El Niño events.

First things first, what is El Niño again? In a nutshell, the term El Niño is used for the climate pattern describing large-scale periodic warming of sea surface temperatures in the central and eastern Pacific Ocean. The shift in warm water that occurs leads to a change in where water evaporates into the atmosphere. This, consequently, alters the flow of the jet stream track. During an El Niño phase, the jet stream typically becomes stronger, and takes a more southerly path across the Pacific. As a result, more storms are brought over to the area of Hawaii, as well as the southern part of the United States. Which brings us to the last part of the equation:

storm → swell → surf → rockon

Apart from more storms due to a shift in the jet stream, hurricanes are also more likely to develop and strengthen during El Niño because of reduced vertical wind shear. Vertical wind shear refers to the change in wind speed and direction with height. Strong changes in wind direction between altitudes can destabilise and weaken a hurricane, and have the potential to prevent it from forming in the first place. Contrarily, reduced vertical wind shear thus means that hurricanes have more chance to develop and strengthen.

So what about the current El Niño? Sea surface temperatures in November 2015 broke records set during the 1997/1998 event, reaching 3 degrees Celsius above usual temperatures. The present El Niño is still increasing in strength, and might very well develop to be the most powerful El Niño to date. Last year, a record number of tropical storms occurred, including an exceptionally large number of type 4 and type 5 hurricanes. The most powerful hurricane, hurricane Patricia, hit Mexico at the end of October blasting at 200 mph, producing 8 metre waves. Hurricanes in the central Pacific have resulted in significant swells along the windward-sided shores of Hawaii, and there has been an above-average tropical surf activity across the Pacific.

Though El Niño is expected to prevail all the way through to spring 2016, the hurricane season in the central and eastern Pacific Ocean has already come to an end. It will therefore become increasingly difficult to catch one of those El Niño-driven mega waves. For those that want to experience real-life jet stream shift, reduced vertical wind shear, or simply want to see breathtaking surf, I’d recommend booking that ticket to the Pacific ASAP. If you’re lucky you might even run into Taylor Knox himself.

References and further reading

Impacts of El Niño and La Niña on the hurricane season
How ENSO leads to a cascade of global impacts
Weather Impacts of ENSO
Hurricane Patricia, More Pacific Storms, and 4 Other Signs of El Niño
Big Wave Diaries: El Niño, 20 Years in the Making

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