SwellWatch forecaster Nathan Cool has been making sense of weather charts and storm maps for 20 years. What started as a free service for friends, turned into a free service for surfers everywhere, with Cool’s Sunday, Tuesday and Thursday updates as consistent as clockwork.

With Hawaii already pumping, and Southern California getting its first big rain event of the winter this week, we started wondering: what sort of weather and waves should we expect on the west coast and Hawaii this winter?

Nobody better to ask than Cool. While most use Netflix or a good book to wind down before bed, Cool stares at global swell models on his computer, tracking purple blobs around the world. “I never take a day off,” Cool laughs. “I’ve watched every storm that’s brought swell to California and Hawaii since 1999.”

OK, let’s have a look inside your crystal ball: what should we expect, both surf and weather wise, for California this winter?

It’s interesting, because surf and weather are almost going to be two different things. Usually, like for an El Niño year, we know what the surf is going to be like, and we know what the weather is going to be like, and both are usually off the charts. And if we talk about La Niña, it’s usually drier weather, and we get less surf.

Right now we’re in a neutral state, though it’s trending a little bit positive on El Niño. So it’s not like we’ve got any real bad news, but it’s just not one of those winters where we expect anything super epic as far as surf goes. But we should still get plenty of good northwest ground swells, because there’s nothing to stop that, like during a La Niña winter. The one thing that happens though, because we’re in a neutral Niño, is that it can actually get a lot wetter than it is during an El Niño. That’s because the jet stream slows down a little bit, and we get more atmospheric rivers. The great flood of California in the 1800’s was during a neutral Niño period.

That’s interesting. I think a lot of surfers in California just assume that if it’s raining a lot during the winter it must be El Niño, and to automatically expect those massive storms and swells.

Exactly. But the two aren’t mutually exclusive. To summarize, it’ll likely be a wetter winter for rain—potentially even wetter than the last El Niño. And as far as the surf goes, we might actually see better quality of surf as well. El Niño tends to bring big swells in at a lower latitude, so we get more westerly swell, but they can also come ashore, and so you’re always hoping the swell outruns the rain and wind. But in this case, those storms should stay further north, because the jet stream isn’t as low during these neutral Niño periods. We might not see super epic surf, but we should still see good size ground swells and overall better conditions.

And what about Hawaii? They’ve been getting a conveyor belt of swell since October. Might that continue?

That’s probably gonna continue. Those storms come out of the western Pacific that hit Hawaii. Once they pass the Aleutians they have a better chance of sending us something sizeable. This winter, there’s nothing stopping that conveyor belt, like you said. When we get into La Niña we’ve got that massive high pressure up in the North Pacific and it’s touch and go on whether or not those storms can develop. During a neutral Niño those northern latitude storms hit Hawaii really hard. Hawaii is poised for more of these northwest ground swells, and they don’t get hit by the atmospheric rivers as much, so there shouldn’t be many bigger rain events. In some ways, Hawaii’s winter will be almost indistinguishable from a regular El Niño as far as surf goes. It might not have those bonkers XXL Jaws type swells, but there’s nothing stopping storm development aimed at the islands.

Good news for the Pipe Masters!

Definitely. Right now, it’s looking like the pattern we’re in should last through spring, so we should see plenty more epic swells in Hawaii.

How about the east coast? Does a neutral Niño affect the Atlantic storm development?

They’re hardly affected, really. El Niño versus La Niña does have an affect on the Atlantic hurricane season regarding swell for the east coast, but that’s over now. However, it does play a part in big surf moving east and hitting Europe, because that’s from the North Atlantic Oscillation, or the NAO, which is the sister of the Pacific Decadal Oscillation, the PDO.

For those unfamiliar, the PDO is these years long cycles. Same with the NAO. And they can trend a certain way for 2 years, 5 years, and even up to 15 years. One thing that’s been keeping us kinda in an El Niño state in the Pacific is we’ve been in a positive phase of the PDO. Remember when we were in La Niña not that long ago? We were in a negative phase of the PDO then, and that helped influence La Niña.

Conversely for the Atlantic, the NOA is in a negative state, so it’s just not as favorable for those really big swells like we saw in Europe in 2016, when the NAO was positive.

How predictive are the cycles, and do you have a general idea of what the next few years might bring?

Things are definitely changing. Whether you want to link it to climate change, or just say the climate is changing, we haven’t seen these prolonged periods of neutral Niño historically. They happen very rarely, and we’ve kinda been lingering in it since the last big El Niño winter a few years back. So, it’s kinda hard to tell. But if we were to go by the decades-long cycles, the positive PDO tells us we’re not going back into La Niña anytime soon, and we may even lean more El Niño over the next few years.