Hurricane Katia Gets Shelved

Stu Nettle
Swellnet Analysis

The Quiksilver Pro New York is currently two days into its waiting period without a single wave being ridden. The organisers have called laydays knowing that Hurricane Katia, which is currently moving north-west between Bermuda and the Caribbean, will provide surf in the coming days.

For an Australian site, such as Swellnet, forecasting the surf from Katia has proven to be more difficult than we first imagined. The problem has been that although a hurricane is essentially the same thing as a cyclone (or a typhoon in the north-west Pacific) each has unique patterns of behaviour owing to local conditions.

For instance, the paths of hurricanes off the east coast off the US closely follow the Gulf Stream. They move very slowly and predictably, especially compared to our notoriously unpredictable cyclones.

Another concern, and this one greatly effects wave height, is the size of the continental shelf on the US east coast. The shelf off Long Beach, New York, extends about 200 kilometres offshore. To compare, the continental shelf on Australia's east coast only extends between 20 and 50 kilometres.

The continental shelf reduces wave height by causing waves to 'feel' the ocean floor earlier and lose their energy. The further out it extends the more wave energy – and hence, more size – is lost.

Hurricane Katia is currently a Category 4 system with maximum sustained wind speeds of around 116 knots. Now, if a category 4 cyclone were tracking slowly and perfectly – as Katia is - toward Australia's East Coast we would see a very large and dangerous swell in the 10-15ft range. It would be the type of swell where only Noosa, Kirra and the Pass at Byron Bay would be rideable.

Yet, as mentioned above, Long Island has a large continental shelf and the swell generated by Katia will lose a lot of its energy before it hits the coast. Because of this we only expect the swell at the contest site to be approximately half the size it would be if Katia formed off our East Coast.

Another factor to consider is that as soon as Katia moves out of the Long Island swell window the surf will drop very rapidly. 24 hours after Katia passes the surf at Long Island will lose at least half the size from its peak. The organisers will have to give serious consideration to this point, choosing their days carefully, if they are to avoid running the finals in small waves.

//STU NETTLE & CRAIG BROKENSHA

Comments

poncholarpez's picture
poncholarpez's picture
poncholarpez commented Tuesday, 6 Sep 2011 at 8:44am

in the second pic, is that another low forming where this one started?

www.sunshinecoastsurfimagery.com or facebook:sunshinecoastsurfimagery

memlasurf's picture
memlasurf's picture
memlasurf commented Tuesday, 6 Sep 2011 at 8:53am

How does the New York shelf compare with Bass Strait? I am from the Mornington Peninsula and we regularly get 8 foot plus surf and have a shelf. The west coast (Victoria that is) is even worst off as it has to bend around to get in there.

Craig's picture
Craig's picture
Craig commented Tuesday, 6 Sep 2011 at 9:15am

@poncholarpez Yes, there's a secondary hurricane expected to form after Katia, but the competition will be over before Long Island receives any surf from this system.

@memlasurf There's quite a difference in the bathymetry between Bass Strait and the ocean floor off New York.

Both (Long Island and Mornington Peninsula) see the 200m depth contour being situated around 200km's from the coast, but off New York, the slope comes up much quicker and shallower, while in Bass Strait a 70m deep channel makes it's way all the way to be only 25km off the coast before becoming shallower.

Here's some approximate numbers.
Water depth 25km offshore Long Island: 24m
Water depth 25km offshore Mornington Peninsula: 74m

Water depth 50km offshore Long Island: 37m
Water depth 50km offshore Mornington Peninsula: 75m

Water depth 75km offshore Long Island: 45m
Water depth 75km offshore Mornington Peninsula: 78m

So you can see that any swell pushing into Bass Strait wouldn't loose as much energy over the same distance compared to if it was moving towards Long Island due to the water staying deeper in Bass Strait while approaching the coast.

sunbay76's picture
sunbay76's picture
sunbay76 commented Tuesday, 6 Sep 2011 at 10:54am

Great answer craig. That article had me wondering how the waves in South Oz pack so much power as the shelf extends a long way out there. It is however about 80 - 100m deep not far off shore. Cheers.

donweather's picture
donweather's picture
donweather commented Wednesday, 7 Sep 2011 at 2:47am

Based on some discussions on another forum recently, I was under the impression that swell models took into account the water depth when predicting swell heights? If so, wouldn't the swell models then predict what swell heights would be hitting the shoreline?

Craig's picture
Craig's picture
Craig commented Wednesday, 7 Sep 2011 at 2:56am

Yes they do, and that's why you'll find that a representation of the swell approaching Long Island drops dramatically in height once it moves into a 50-100km radius out from the coast.

thermalben's picture
thermalben's picture
thermalben commented Thursday, 8 Sep 2011 at 9:45pm

Jeez, what an ordinary round of surf from a Hurricane swell!

lolo's picture
lolo's picture
lolo commented Friday, 9 Sep 2011 at 1:18am

Is that as good as its going to get?

From all the hype Katia was perfectly positioned to give them some awesome swell. Was that all just BS or did it weaken or head the wrong way?

thermalben's picture
thermalben's picture
thermalben commented Friday, 9 Sep 2011 at 1:23am

The swell's expected to peak overnight (locally) and then ease rapidly during Friday. Looks like the surf was 3-5ft today, so maybe we'll see some stray 5-6ft sets early tomorrow - but otherwise that appears to have been the best of it.

the-roller's picture
the-roller's picture
the-roller commented Friday, 9 Sep 2011 at 1:26am

Hurricanes come not only in all shapes and sizes., but the resultant surf is formed by the effects of particular beachie they strike.

Even though there was no BMXing, or skateboarding, or rock concerts, people came out in droves on the beach and on the world wide web cast for this event which was strictly about surfing NYC....

Into the quarters we have one Yank, three Brazilians, and four Aussies.

Someone is going to pull a check for $300,000 for a weeks worth of surfing.

Yew!

thermalben's picture
thermalben's picture
thermalben commented Friday, 9 Sep 2011 at 9:36pm

Looks like the surf peaked overnight on Thursday (local time); the biggest wave I saw during the event was 5ft. At least the Final Day delivered offshore conditions! Although to be honest I don't know how much more size Long Beach could have handled whilst maintaining quality - 3/4/5ft seemed to be an optimal size for the shape of the wave.

fitzroy-21's picture
fitzroy-21's picture
fitzroy-21 commented Saturday, 10 Sep 2011 at 12:35am

Wow roller,

So incredibly grateful of your constant bombardment of internet wisdom of late. Without it, so many of us would have been rendered clueless.

I particularly have enjoyed your intolerance to other users points of view and the resulting harrassment/bullying. So refreshing.

Cheers

the-roller's picture
the-roller's picture
the-roller commented Saturday, 10 Sep 2011 at 2:52am

Not a problem, fitzy. Now if you'll recall, many nozzles like old rottkamp were constantly calling not only the ASP, but this Quiksilver NYC comp a total failure well before it went off.

Forgive me for pointing out when a douche nozzle dribbles.

blasphemy-rottmouth's picture
blasphemy-rottmouth's picture
blasphemy-rottmouth commented Saturday, 10 Sep 2011 at 3:22am

@Fitzy,

And don't bother using logic... it doesn't work on this... thing you are talking to. I've already warned Stu... it's his problem now.

Good luck guys.

the-roller's picture
the-roller's picture
the-roller commented Saturday, 10 Sep 2011 at 3:53am

Speaking of logic and facts, what was that you were saying about the impending failure of the Quicksilver Pro NYC?...

As both Bob Slater, and Owen Wright, half a million New Yorkers beachside, and those millions of online viewers would all collectively disagree with you right about now, ms. Rottkamp.

Yew!

blasphemy-rottmouth's picture
blasphemy-rottmouth's picture
blasphemy-rottmouth commented Saturday, 10 Sep 2011 at 4:17am

I am not myopic Roller. This contest has issues being the scenes that you cannot imagine. You are, as always, on the wrong side on the debate. Your mind, what's left of it, will be blown very shortly... and it's a big "I told you so."

It's not going to come from my lips.

It will probably be Network News. Where real journalists work.

the-roller's picture
the-roller's picture
the-roller commented Saturday, 10 Sep 2011 at 4:23am

"Being"? heh.... Sure, rottkamp, sure.

Speaking of myopic, get back in your bottle already. You sound drunk again as usual.

"Central Park is more like Central Forest"...

http://vimeo.com/28834591

blasphemy-rottmouth's picture
blasphemy-rottmouth's picture
blasphemy-rottmouth commented Saturday, 10 Sep 2011 at 4:32am

It's amazing what one post, listing the failures of the face of Surf Media, will do to one's email Inbox.

Your love affair of The Industry, should be cherished with every dying moment.

People from outside the establishment have very sharp pins aimed at the bubble you worship. Far sharper than anything I have...

Just saying...

I've only been warning people for about two years now. And Andy Irons legacy is going to leave so much more than surfing to future generations. That's the good news.

the-roller's picture
the-roller's picture
the-roller commented Saturday, 10 Sep 2011 at 6:01am

Ms. rottkamp,

Sure dude, we've seen your type many times before.

Thanks for your "warnings".

Back to your vampires and fairy tales....

Drive thru.

http://www.youtube.com/watch?v=db4HOzxVtHM&feature=mfu_in_order&list=UL

http://www.youtube.com/watch?v=zhYrSF3ubBc&feature=related

the-roller's picture
the-roller's picture
the-roller commented Saturday, 10 Sep 2011 at 6:03am

Ms. rottkamp,

No worship here, mate. Just the facts and opinions..

Fugetaboutit...

Not only will the surf media, but the surf industrial complex, the governing body, as well as competitive participants, all be around long after you and I are done and dusted.

Well long after your drug and alcohol soaked opinions fade from the meaningless commentary sections of any give website.

Get used to this fact, bru.

Yew.