Nazare Blast: Wind Dictates Play

Ben Freeston

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Updated 1965d ago

18ft of swell and 15 seconds period for Friday at Nazare. That's got to be a record right? Not quite. This isn't Hawaii, sitting well south of a typical storm track, in fact Nazare sits almost two degrees of latitude north of Mavericks. The story here is similar to its distant Californian cousin: Giant days in winter are guaranteed, what's less likely is dodging the storm winds as they arrive.

With 30 years of hourly archives it's easy for us to bring context to a swell. For this one, despite the numbers looking more than interesting, the story for raw swell size really isn't that impressive. Nazare records show 333 days of swell hitting or exceeding tomorrow's peak over 30 years. That's 11 days a year on average if you can't do the maths. More than enough to make this almost 'business as usual' for a typical winter. Plug in light or offshore winds and those numbers change considerably - the risk of landfall for storms of this size is high and has been a particular theme of the last couple of years.

Despite hints in the forecast that tomorrow might play ball there's still plenty of risk in the numbers. The problem is, the storm creating the swell will sweep down the coast bringing onshore winds as it passes early on Friday morning. The tiniest shift in timings and path, even at this stage, can substantially effect the outcome but these winds are expected to last beyond first light. The good news is we've seen on recent swells that it doesn't take much offshore to clean things up, at least for towable conditions. But there is an increasing risk this will happen, if it does at all, into the afternoon or even the evening, which could turn a potentially legendary day into another one of a large handful of huge but unsurfable days each year.

Forecast Tip: As a very rough guide, the relationship between swell size and period is a useful one to understand how close a storm is likely to come to the coast and how high the risk of disruptive winds might be. Here, the fact that 18ft of swell is larger than the period is a clue this is an impact situation. Think 10ft @ 20 seconds in Hawaii on a distant, groomed groundswell on the other end of the spectrum.

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