Check out this short article on South Florida's Refraction Swell. 

http://www.atlanticsurflife.com/026_refeaction.php

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" Water is an embracing medium" Jacques Cousteau

Some fun wave porn in that article, but I don't think refraction swells involve swell 'bouncing' off of the bahamas. But that's all the fun in the mystery.

 

Is that Delray going off? There was a pretty fun swell this recent winter there...

"This is how it works to my knowledge when a cold front pushes into Florida and the winds pick up out of the North West a swell will generate rolling towards the Bahamas and sliding down the coastline. The wind needs to blow heavy offshore for a long period of time, right? Yes, offshore winds can create waves! This is when the Gulf stream starts bouncing and the horizon looks like a group of elephants dancing on the horizon. The swell generated from the North West winds will either bounce off the Bahamas or bounce off the Gulf stream sending perfect swell to the South East Coast of Florida."


COMPLETE and utter BS!!

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"Most people would die sooner than think; in fact, they do." - Bertrand Russell


"Morality is doing what is right, regardless of what you are told. Religion is doing what you are told, regardless of what is right.


If I do not answer you .... nothing personal, I just have you on ignore.

Finally some feed back from the Forum! Tell us how it works LBLarry? Please I've never witness it...

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" Water is an embracing medium" Jacques Cousteau

A perfect set-up for "refraction action" is NW(320deg.) wind blowing at 25knots gusting to 30 for at least 12hr period. But ive seen perfect chest high refraction with only 15 knots wind for about 8-10 hrs. like he stated u can be in delray and it can be head plus and boca is only waist high funkness. Dont know the science behind it but the deep shelf and gulf stream gotta be major factors!! cought some great refractos in some hard bottm beachs in lake worth this winter

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Creme de la Creme
Stoke to all and to all a good night

The very notion that a NW wind could create enough swell in a 5 - 20 mile fetch (distance to the gulf stream depending on location) and bounce back to shore ... or go 90+ miles and bounce back 90+ off the Bahamas is a ridiculous urban surfing myth.

It is simply swell angle created by mid / north Atlantic low pressure systems and timing of the NW wind created by the frontal system associated with these lows. While it is somewhat true that the Gulf Steam will help steer these swells into some breaks and not others ... the biggest factor(s) are again the swell angle (in degrees) and if or not a particular breaks near shore & off shore topography picks up and funnels the swell to that break.

Refraction can and is a factor in a surfing break. Such as offshore trenches funneling swell or the biggest and easiest example is a point break. Where the swell is in fact refracting around the point and breaking down the line. However .... refracting back to shore .... no.

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"Most people would die sooner than think; in fact, they do." - Bertrand Russell


"Morality is doing what is right, regardless of what you are told. Religion is doing what you are told, regardless of what is right.


If I do not answer you .... nothing personal, I just have you on ignore.

Oh man I love when peeps bring this up cause I know exactly why it happens.  Its a problem of wave dynamics and is easily explained.  First of all whoever named this thing, "refraction swell", knew how it worked.  The key word is refraction, NOT reflection, which is how about half the people try explaining this thing (swell bouncing off bahamas or gulf stream or whatever).  This is not how it works.  Its simply the same type of physical wave processes happening that happen at many pointbreaks (e.g., rincon, CA) but on the regional scale (south florida).  WPB is the furthest point east south of cape hatteras.  This means you can have a nw wind as far north as  off the coast of cape hatteras pointed directly at WPB.  Think about it, thats plenty of fetch.  Once the swell hits WPB or just north of it, the swell will turn with the coastline pulling the waves into the WPB area and breaks to the south.  The gulf stream merely provides deep water close to shore so little energy is lost to friction as waves bend and come onshore.  

I agree with K7. Palm Beach is like 45 miles East of Cape Canaveral. with those strong NW winds and the canaveral buoys bouncing 10 feet, where do you think that swell is headed? Deep water off of Palm beach with proximaty of gulf stream, and local land mass swell bendage (refraction), then you have surf. The hit-n-miss is tide dependent and swell angle and duration. It still is a semi-mystery however. Nature and weather will always be.

WPB is located at 75degrees W, Hatteras is located at 80degrees W. At 57 miles per degree (at 35 degrees N), Hatteras is apox 280 miles EAST of WPB Now explain to me how a NW wind can blow from Hatteras directly down to WPB??? Take out a damn map and draw yourself some NW lines on it!!




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"Most people would die sooner than think; in fact, they do." - Bertrand Russell


"Morality is doing what is right, regardless of what you are told. Religion is doing what you are told, regardless of what is right.


If I do not answer you .... nothing personal, I just have you on ignore.

Edited: 05/07/2011 at 02:46 AM by LBLarry

PB refraction is from swell bouncing off da Bahamas?
lol

1st... more swell there...
PB sits a lil further out and catches more of the passing northerly swell than Cocoa Beach does.

2nd ... bottom contour makes a dif...
Bottom is super deep there and drops off even deeper just past the break there than most anywhere else in Florida. That's what causes some bending of the northerly swell there.

Bounce the Bahamas bounce theory

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... positioning and selection

No refraction.

Wind blows from one direction, the swel then constantly bends to the rigfht.

Coriolis effect.
http://en.wikipedia.org/wiki/Coriolis_effect

Always hit or miss down there and I kind of understand the dynamics BUT I don't understand why Miami gets so hollow and perfect. Sure a hurricane swell has the power but a north swell on a beach break? Deeper offshore down there?

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Need more water time. Plenty of time left to make $$

Yes, mostly Coriolis effect. Then, , , , we can start talking about the "refraction" off of the Gulf Stream and the swells interaction with the coastline when it starts to "feel" the bottom.

And, again, , , , the "elephants on the horizon" is not a "large swell heading south". Some swell, yes, but it is mostly just "chop"; that we see "magnified" by the atmospheric bending of light from over the horizon. Otherwise, called a mirage.

CHECK THIS OUT!: Great Lakes Mirage

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Dora Hates You

Yes excuse me LBLarry a nw could blow at WPB as far north as charleston, sc (where it would be due north), not hatteras.  But think about it, if a front is pushing off the sc/ga border and if its angled right it could have already pushed off hatteras and winds could already be ne up there aimed at wpb (if not oh well there's still hundreds of miles of fetch along the florida coastline that the swell travels parallel to and builds along).  Corilos can only help but its effects are always small for any problem (i.e., it's gonna take more than coriolis to bring the nw swell onshore in south fl).  For the inconsistency at breaks it just how the bathymetry funnels the swell onshore and where the energy goes or doesn't.  South fl has alot of hard bottoms and not just close to shore either so this would make sense why it's more hit or miss than in central and north fl).

This is always a hot heated topic for some reason.  I guess because there's no real study that came up with an well defined answer and people like to debate their ideas. I'm sure there are people who don't think the providence channel swell happens eather, but yet...delray 10', everywhere else, flat.

It's probably a number of different processes going on.  The fact the gulf stream is opposing the swell (flowing north) and bulges a bit higher than the water around it,  The proximity of the bahamas, The way Florida bends back west and PBC sticks out, refractoin, reflection....again, ALL of these things probably play a role which is why it is hard to predict. 

It doesn't always happen either....We had a time this winter where the NW wind was howling for 24hrs, and nothing happened.  I've seen it with a straight west wind too....if it blows hard enough.  Mother natures little secret I guess.  Who knows.  All I do know is that 8 out of 10 times it DOES happen, so something is going on there.

As a meteorologist and south Florida surf forecaster, I can tell you that sometimes when we get this swell, THERE ARE NO WINDS OR FETCH POINTED AT US, BEFORE, DURING, AND AFTER THE COLD FRONT. Not out in the atlantic, not in the northeast, nowhere.  So it is NOT as simple as winds blowing our way as some suggested.  I can go back and get the charts, there just isn't any fetch at all.

It is curious that there is a delay of 12-18hrs though.  Maybe it needs the seas in a mature state in order for the magic to happen.

Also, look at this picture below.  Don't think that waves can bend around at 45 degrees and go the other way?? 

Now look at the next picture and imagine grand bahama on the right and florida on the left....and the same little opening pinches off and refracts the waves.

 

 

 

Now, again...I don't  think this is the only thing going on, it's probably a number of things...

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WPTV NewsChannel5/Fox 29
Meteorologist/Surf Forecaster
Environmental Reporter
Palm Beach County, Florida

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Nicely done, jw. That should put it to bed.

 

Pretty much: sustained NW winds for 24 hours... go take a look.

Unfortunately, there hasn't been much action in SoFlo (Refraction or otherwise) since January anyway. November and December came through nicely and then summer started first week of January. Worst I've seen it in many years. I really need to move. Even if it's just 45 minutes norte.

 

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Bringing out the science! 

I don't understand why, with the angle of South Florida ...say Jupiter and southward, Sofla isn't like the Superbank all winter (swell pending).  It always seemed to me like north swells come down and spots in south florida are stand completely perpendicular to the swell, they should break no matter what.  Obviously, this isn't the case at all.  We can see a 4-6 ft north swell going crazy in the gulf stream a few miles away and on the shore...well, weak 1 footers running parallel to the beach...not like a point break, tapering down until is runs parallel and either fizzles or closes out.

So, I don't understand why South Florida onward doesn't look like this pic of Lake Worth all winter?

http://ww.surfline.com/travel/surfmaps/us/florida_south/images/dugan_lakeworthpie.jpg

I don't know much swell size matters either because I've surfed some 1 ft waves at Rincon and C-Street in Cali where I've gotten several cutbacks in before it dies.  The swell that day in cali was only 1 -3 ft northwest.

So, again, I don't get it.  I go to bed, hoping for some waves in sofla, the forecast calls for 4-6 ft.  I wake up, check every spot from boynton beach to jupiter inlet and settle, heartbroken, to somewhere in riveria beach.  But I can see the 4-6 surf going crazy out there...just not getting into shore. 

Assuming refraction or reflection exists (which I'm very inclined to believe it does)...why doesn't it work on a "sure-thing" day instead of skunking the whole florida coast? 

what a great topic...being a fla local native whatever -in the 30 yrs of surfing da sunshine state let the refractyo mystery go on and on ,jus think a smaller version of this is why boardwalk can be sideshore overhead bombs rippin' down the beach and cb pier is chest high clean ,its the bend the cape hook ??? i mean sometimes you can waste a full tank of gas and a day with nadasurf  or get perfect surf with a handfull of crew or surf with the whole damm state at one break . regardless searching the swell round the state is dope stuff weather its providence channel  hurricane swell down delray when everyelse is flat sic north swell down sobe big brevard lines wpb mega lines cold jax pier even gettin wavepool waves in the gulf (n some times sic sic hurricane and front waves)inda gulf, were stoked...so no matter how it works jus be on it and you got it all figured out-

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hittn'ripz-n-rippn'hitz

jwieland demonstrated the concept nicely.  mathematically it is reffered to as the Huygens-Fresnel principle. in the simplest terms, this states that every point along the wavefront generates secondary waves. if we were going to be precise, we should call it a "diffraction" swell. diffraction is a concept related closely to how wavelets propagate through a "window" aka that body of water between florida and the bahamas.

these two links should help expand

wiki: http://en.wikipedia.org/wiki/Huygens%E2%80%93Fresnel_principle

the diffraction animation on bottom: http://physics-animations.com/Physics/English/int_txt.htm

no bouncing

"Refraction is the change in direction of a wave due to a change in its speed. This is most commonly observed when a wave passes from one medium to another at any angle other than 90° or 0°. Refraction of light is the most commonly observed phenomenon, but any type of wave can refract when it interacts with a medium, for example when sound waves pass from one medium into another or when water waves move into water of a different depth."


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"The truth is incontrovertible.
malice may attack it,
ignorance may deride it,
but in the end,
there it is." -Sir Winston Churchill