El Niño: The Winter Outlook

Ben Freeston

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Updated 1557d ago

We’re on the very edge of an extreme El Niño event set to bring potentially outsized winter surf, particularly to the North Pacific. But despite a build-up of unusually warm water in the Pacific a repeat of 1997 / 98 isn't guaranteed. In fact the current state of the ocean is unlike anything we’ve ever seen before.

  • We now have the strongest El Niño event since 1997.
  • El Niño will almost certainly last all winter.
  • We could see an event of the scale of 1997 but it's not guaranteed.
  • As well as a large body of warm water in the Eastern Pacific we have exceptional Central Pacific temperatures.
  • We can very reasonably expect overall larger and more frequent storms on a more southerly track in the North Pacific this winter.

For over 100 years, long before the advent of satellite surface monitoring, sailors and fishermen have been noting the seasonal occurrence and effects of an area of unusually warm water off the coasts of Ecuador and Peru. With the advent of detailed sea surface temperature records we’ve been able to put hard data to the concept, but are still a long way from a complete understanding of the phenomena.

How does El Nino create giant surf?

In large part our climate is driven by the temperature difference between the warm equator and the poles. Warm air rises in the region around the equator and flows towards the poles, where relatively cold local air is sinking. This 'Hadley Cell' somewhat simplifies the circulation, but for our purposes it explains why winter creates larger surf than summer: The equatorial air is, generally, a similar temperature all year round, but as the Northern Hemisphere angles away from the sun in winter the polar region cools and the difference in temperature is increased. With circulation dependent on temperature difference the flow of air increases, magnifying the jet stream wind and the conditions for extra-tropical low pressure systems to develop and create surface winds that drive waves towards our coasts.

El Niño increases this circulation by adding anomalously warm water to a large area of equatorial water in the Pacific. With both cold winter polar conditions and an enhanced equatorial temperatures we see (all things being equal) a stronger, more southerly jet stream and stronger, larger winter storms creating westerly swell for Hawaii and the US West Coast.

We’ve already talked about the Southern Pacific entering an El Niño phase. Scientists quantify the extent and variation by monitoring average temperature variation over several critical regions of ocean. Because our reliable understanding of the whole ocean has only been possible since the advent of satellite monitoring we have only a little over 40 years of continuous records and the more data we gather the more complex the picture becomes. While originally we looked for confirmation of this same pattern of warming in the Eastern Pacific first noted by local fishermen we’ve more recently seen a different pattern, anomalous warming in the central Pacific but cooler water near the coast, named ‘El Nino Modoki’ and this seems just one other possible variant.

For this year we have, at this time, an El Niño looking unlike anything we’ve seen before. With an anomalously large build up in the Central Pacific and a warm water in the Eastern Pacific that is well into the strong El Niño range but not yet comparable to the extreme events of 1997 or 1983. The latest WMO guidance suggests that a likelihood is an event in the top four of those we've seen since our records began, however further weakening in the easterly trade winds could tip us into an extreme event beyond those we've recorded to date.

Warm conditions in the Eastern Pacific combine with exceptional temperatures in the Central Pacific.

Warm conditions in the Eastern Pacific combine with exceptional temperatures in the Central Pacific.

© 2019 - climate.gov

The bottom line is we don’t know exactly what will happen or what it'll mean for surfers. We don’t know at this stage if we’ll see an event similar to 1997 and we also don’t know exactly what effect the current state of ocean temperatures might have on wave climate, because we’ve not recorded it before. What is apparent to anyone glancing at sea surface temperature charts is that each winter has its own signature. We can very much expect a more active NPAC season than last winter given the extra warmth at the equator, in fact while we may not have a classic El Niño it's not immediately clear that the wider band of anomalously warm water won't mean better conditions for the development of large storm systems. Equally while we do have this band of warm El Niño around the equator we also have unusually warm waters much further north which could even act as a damper on our achieving the kinds of swell averages we saw in 1997.

What’s fascinating is the relative insignificance of our data in understanding these phenomena. Surfers are often given to speaking of a swell or run of weather as unusual, even exceptional, but in climate terms our recollections are a blink of the eye. Even with 40 to 50 years of detailed data we’re seeing no more than hints of patterns - that’s nearly a lifetime’s surfing for many of us. While El Niño itself is a cyclical phenomena its development is impacted by other climate cycles, many of which can operate on multi-decadal or longer time frames. And even within the short 40 year window of analysis here anthropogenic global warming will have an effect that'll make comparisons with relatively recent events subject to error. Consider the ground that's shifted in the big wave scene in the last giant El Niño of 1997 / 98: The maturing of the tow scene and the resurgence of paddle surfing as perhaps the dominant movement in the exploration of giant waves. It's humbling to think that all this has occurred in what may be just one short climate cycle and that records are being set in years that, by historic standards, probably didn't offer the biggest or best conditions. This winter should provide opportunities to further explore the limits in the testing grounds of the North Pacific.