El Niño, the pattern of above average Pacific sea temperatures understood to influence much of the planet's climate, is back and looks set to stay a while. Some predictions suggest a winter in which we might see a stronger effect than felt for years, a mixed blessing for surfers in the Pacific and potentially bad news for surfers on the US Eastern Seaboard.
The Latest Forecast
Forecasting El Niño is something of a dark art. We're interested in the heat below the surface and how the ocean winds might drive this towards the surface, but those winds are also dependent on the ocean temperature as a driving force. This feedback loop amplifies the chaos inherent in the system. Currently sea surface temperatures in the central Pacific region are about 1 degree above the average long term value.
However forecast models have been increasingly confident in these increasing and the Australian Bureau of Meteorology is among those firmly pinning its flag to the mast, suggesting that even the average modelled outcome should see us with an event amongst the largest in the 35 years since records began. However forecast models have been increasingly confident in a strong event and the Australian Bureau of Meteorology is among those firmly pinning its flag to the mast, suggesting that even the average modelled outcome should see us with an event amongst the largest in the 35 years since records began. In fact it had to tweak its website because the predicted numbers have pushed off the usual scale on the graphs. In the Northern Hemisphere Axel Timmermann of the University of Hawaii in Honolulu spoke with the New Scientist: "We have this enormous heat in the subsurface that is propagating eastward and it's just about to come to the surface. I looked at the current situation and I thought, oh my dear." Arguably agencies with a responsibility for severe weather alerts are hedging their own liabilities in predicting this kind of event early given the damage it can do: a broader spread of models falls in below the BoM's average outlook and last year saw a call that didn't really materialise. However a bet on anything other than a strong event would be the longer odds proposition at this stage from our reading of the data.
Of all the longer term climate cycles that affect our weather the warming and cooling of the sea in the central Pacific, that we call El Niño and La Niña respectively, is one of the better understood. More importantly we can tie together the science and specific studies of wave climate all the way forward to our practical experience as surfers and surf forecasters. In this respect it's one of the most tantalising glimpses beyond the 16 day deterministic modelling we're able to offer. The effects are different for surfers in different locations:
For surfers in the Pacific El Niño can be a positive development - depending on their appetite for larger waves. El Niño conditions typically result in a stronger and more developed Jetstream and a more southerly track. This is the engine that drives the development of North Pacific storms and the resulting swells that pound the winter shores of Hawaii and West Coast US and send long period ground swells down into Central and South America. There are pros and cons to an El Nino winter - these same storms tend to follow a more southerly track towards California: Westerly swell reaching less exposed coast is an upside with onshore winds and bad weather the bad news. For the average surfer there'll be winners and losers - for the big wave contingent there should be some sense of excitement given the outlook and recent and ongoing developments at the boundaries of big wave paddle surfing.
Given the proven link between El Niño and the North Pacific wave climate it's no surprise that we can tie strong El Niño events to specific swells and giant surf. In the last 20 years we've experienced two significant El Niños and the winter of 1997/98 was, scientists believe, the strongest in more than 50 years. The chart below gives a great idea of the power of that enhanced Jetstream to spit out significant storms. The first in the sequence is not only huge, but it's proximity to Hawaii is even more unusual. This swell saw Ken Bradshaw ride what was, at the time, the biggest wave ever surfed at Outer Log Cabins in Hawaii. The nearest wave buoy at the time registered 27ft @ 20 seconds.
We can also be confident in is the increased likelihood of Pacific Hurricanes. Warmer local waters and decreased winds increase convection, the fuelling process for warm-core storms. Whilst these storms can come too close to the coast (or run uselessly out to sea) to offer meaningful surf their frequency should increase.
Here the news is mixed. El Niño conditions give rise to wind shear - different wind speeds at different heights. These winds act to pull apart the rotating vertical column of warm air central to the development of a tropical storm. The Met Office latest guidance suggests a below average season with five hurricanes which will have an impact on late summer and Autumn surf. However the repositioned Pacific Jet Stream tends to increase the number of Nor'easters, extra-tropical winter cyclones forming on the US East Coast and also push the peak strength of these later into the winter. These storms are a source of decent winter conditions on the US East Coast but also a feed of more southerly swell to south facing spots in Europe. Overall, all other factors being equal, expect less swell in autumn and possibly early winter and more in late winter.
Of course the link between this climate cycle and the intricacies of the weather on a day to day basis is statistical. El Niño winters aren't the sole preserve of giant swell and while The Eddie may have last run in an El Niño winter there have been plenty of standout big wave moments in the La Niña years in-between. Nonetheless the current outlook does raise the interesting possibilities of conditions that'll allow for boundaries to be pushed yet further in giant surf this winter.