Thursday, December 06, 2007


Rainy weather continues in Maui.

It rained hard all day yesterday and it looks like more of the same today.
Here's a satellite pics that shows the front. It passed quickly over Kauai (where it's now sunny) and Oahu, but it got stuck over Maui and the Big Island...

As a consequence the wind is still blowing Kona and I might be missing out on some extreme wavesailing at Kanaha... Northwest of the front, in fact, the winds have been blowing strong from the north over an almost stationary fetch for quite a while and that created some huge surf again. The NW reported a reading of 28.5 feet at 15 seconds from the north yesterday. That's the biggest I've ever seen.
The surf won't be clean though. The short distance from the source, will mean that also the energy at lower periods (that usually dissipates when the swell come from the more remote NW storms south of the Kuril islands) will make it to our shores and the breakers will be rough, confused and with dangerous currents.

Anyway, that 28.5 is the Significant wave height and is calculated as the average of the highest one-third of all of the wave heights during the 20-minute sampling period.
Mmm... what does that mean?
Let's have a look at this other chart that shows how the energy is distributed throughout the different periods.

Even though it looks like about 80% of the energy is concentrated around 13-15 seconds, there's also a 20% of it around 10 seconds. And that means two things:
- that 28.5 is not all related to the 15 seconds waves
- it will be confused breakers
Not clear yet?

Let's have a look at this chart from Surfline that shows the real height of the swell at the different periods.

The black thin line shows the reading of the buoy as available on the NOAA page.
The red line is the 15 seconds component. It went over 20 (but not 28.5) in the afternoon of Wednesday and it's still hanging in there at around 20... those waves will be massive on the reefs. The bigger the period the more the amplification factor.
Based exclusively on my experience, these waves can generate 30 footers at Lowers, 40 footers at the outer reef at uppers and at Hookipa, 60-70 footers at Jaws.
But what about the green line? That's the component of the swell at 10 seconds and it's about 10-15 feet!!! Now, that's going to make a huge mess out there with confused breakers, strong currents and rouge waves (when the peaks of a big 15 second wave and a big 10 seconds wave will coincide upon breaking on the reef).

Of course the webcams would help (they're all down today... must be the storm...). And unfortunately also the Waimea buoy seems to have stopped working... it probably took too much pounding! It may be months before they can fix it...
But see how many things you can deduct already?

Right, still nothing compared to all the other variables.
Again, the wind is blowind Kona in Maui and that will clean up the surf a lot on the north shore.
The NW buoy is NW of Kauai and the fetch was oriented north to south that means that that swell can miss Maui to the west big time.
In other words, it's good (and fun) to try to predict the weather, but sometimes you just got to go to the beach... and since it looks like it's temporarely clearing, I may well do that.

First, some colorful windsurfing photos. This is a little sequence on a beautiful wave at Hookipa. Thanks to Kris Mills.

Not radical at all, but rather relaxed... being an old fart, I'm pretty happy about it!
Here's instead how much more aggressively Diony hits the breaking lip to get some air.

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