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Adam Wright
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(Saturday) 1.5.13

Why did that North Pacific storm, that was supposed to have swell hitting around New Year’s, crap out?

Pete Asked: What happened to that North Pacific storm that was supposed to have swell hitting around New Year’s? It crapped out, obviously, but why?

Adam Wright – Solspot Forecaster:

Hey there Pete!

No kidding about that swell crapping out…definitely not the way we would have liked to start 2013…it is nice that the following storms managed to kick out the fun size swells we are seeing right now (Jan 3-5).

Here is the weather-nerd post storm breakdown:

Basically there weren’t one or two simple things that caused that swell to bust…if it had been something simple all of the forecasters would have caught it and adjusted for it.

The funny thing is that when I look back at the data that we got from the actual remote-sensing tools, (buoys, satellites, ship reports, things like that), the storm’s output makes sense…it actually produced about what it should have based on its position, intensity, and track…it just happens that what the storm was doing and what the “weather and wave-models” said it was supposed to do were two different things. I would say that this wasn’t really a case of the swell going bust, but a failure in the computer models and the lack of fresh data for the human forecasters to adjust to it.

Check out the long-range updates I had posted prior to the swell…you could see that I was pumped up by the storm’s forecast (like we all were) last week. (Oh and we keep all of the old forecasts accessible on our site, in case you want to check out our accuracy or find out what sort of swell mix made your spot fire.)

http://solspot.com/content/southern-california-long-range-surf-forecast/adam-wright/steady-swell-on-the-way-for-the-weekend-and-a-crazy-looking-storm-starting-to-spin-up-in-the-long-range-charts

Here is a chart from that forecast…you can see how the swell model was cranking up the volume.

But then I started to get a bad feeling about things on Monday as the initial bits of data were coming through…not enough to downsize the swell to more realistic levels but at least shaving some of the hype off…

http://solspot.com/content/southern-california-long-range-surf-forecast/adam-wright/starting-off-2013-rightwith-offshore-winds-and-building-wnw-swell

Check out how different the model image was from the 60-hour forecast to basically the analysis chart (the 00-06 hour forecast charts.)

The craziest part is that wavewatchIII (NOAA’s wave model that every forecast site uses as the core engine for their models) continued to overcall the swell by nearly 30-40% even as it was arriving…granted their number one goal is to keep people/property/commerce safe from bad weather, so overcalling something isn’t a horrible thing for them…sure they like to be accurate, but most importantly they want to make sure that people don’t get hurt. It was this glitch, or failure if you will, of the model that had everyone so worked up…having the holidays in the mix probably didn’t help either.

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When you get to the storm itself…the computer wave models expected that storm to build up 45-50 knots of wind as it moved into position NNW of Hawaii, which it actually did manage to do. It was this part of the storm that produced the long-period swell that we had filling in late on Monday evening and through early Tuesday.

The kicker was that, according to the swell models, the storm was supposed to maintain those speeds and track across the mid-latitudes toward Socal before breaking off and heading through the Pacific NW. In reality the storm dropped the core winds to about 30-35 knots as it moved into position NNE of Hawaii and started to change shape. What was happening is that it basically ran into the strengthening ridge of high pressure in the NE Pacific (the ridge that was beginning to set up the cleaner wind/weather conditions for California.) The sudden lack of fetch length and the rapid decrease in intensity gutted the storms ability to produce swell…so all of the medium-period energy that would have been the meat and potatoes of the “big swell” the models were calling for were not pushed out before the storm crumpled.

In the simplest of terms the storm flared up, got off a hip-shot of long-period NW energy and then collapsed without the follow-through. The long period energy hit the buoys at the right time, leading us on with the idea that the rest of the swell was following behind it. But in reality with the storm falling apart there was no following swell, the rest of the energy failed to show, which is why it sucked for us surfers so much more.

The one last thing that played a role in my own forecasting is that the California Buoy, (#46059 that is “supposed” to be located about 500 miles offshore of San Francisco), tore loose before the summer of 2012 and hasn’t been put back in service yet. If that buoy had been in place it would have given us human forecasters at least a 12-24 hour heads up that the swell wasn’t going to show…not sure if that would have been enough time to diffuse the hype/rumor machine that was already in full swing…but not having it there didn’t do us any favors.

Like I said…it was a bit of complicated mess, hopefully this makes some sense.

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