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appendix : wave
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Willard Bascom :
Estimating Breaking Wave Height
INTRODUCTION
Measuring the height of a breaking wave (a moving object
constantly changing shape) has been a consistent discussion topic
amongst surfers.
In Surf
and
Sea (1965), John Kelly Jr. proposed two
ways of measuring waves - "you can over estimate or you can
under estimate."
Most importantly, a basic scientific
method was detailed by Willard Basom in his seminal
work on wave research, Waves
and
Beaches (1964).
DEFINITION
Breaking wave height is measured on the
face, from sea level to the waves maximum crest.
The face is measured because:
1. the action of the face causes
erosive action to the sea floor and the beachfront.
2. the action of the face
impedes a surfers' progress out through the surf.
3. the face is the slope on
which a surfer rides.
Measurement taken
from the shore allows:
1. fixed
reference
points.
2. confirmation by a second
party.
3. measurement of a maximum
range
4. size and period are measured
from the beach before entering the water, a significant safety
feature.
THE BASCOM METHOD
"Simply
stand on the beach face at such a level that the top
of the breaker is exactly in line between your eye and
the horizon. Then, as shown in Figure 56 (below),
the vertical distance between eye and backrush curl
(which is about the same as the average sea surface) is
equal to the height of the breaker."
BASCOM'S DIAGRAM
FIG. 56. When the observer's
eye is aligned with the top of the breaker and the horizon,
the vertical distance between
the eye and the backrush is equal to the height of the
breaker.
Bascom : Waves and
Beaches (1964) page 173
EXPANATORY NOTES
1. The Peak of the Wave (kulana
nalu)
a. As a swell approaches the
shore, friction with the bottom causes the wave to become
progressively taller, reaching maximum height just before
breaking.
In most situations the largest waves
break furthest from the beach.
This illustrated by....
FIG. 53. The breaking of
a wave :
1. Swell peaks up on entering
very shallow water.
2. At depth equal to 1.3 times
the wave height, it breaks.
3. Wave re-forms and breaks
again.
4. Water moves beachward as
wave of translation.
5. Finally rushes up the beach.
Bascom : Waves and
Beaches (1964) page 160
b. Most surfing waves, after
breaking, maintain a peak profile with the maximum height in the
crest.
Outside of the crest, the shoulder is in deeper water and is
smaller.
Inside, or behind, the crest the broken wave is whitewater (nulu
muku), transformed to a wave of translation, and is also
smaller.
Note that, for simplicity, the diagram above does not include
the respective wave troughs
.c.
A surfer may not always ride in a position at the waves maximum
size.
In the photograph below, the wave is largest for the red
shorted surfer, smaller for yellow
and smallest for blue surfer
Australian National Travel
Association, from Klein: Surfing (1965)
pages 176 and 177.
Coloured board shorts added.
2. The Back Rush Curl
The back-rush curl or back-rush wave is
the small wave that finally breaks before the wash rushes up the
beach.
This gives an estimate of the current
sea level, as distinct from the extent of the wash which has a
great variation.
3. The Horizon
In normal visibility the horizon is
approximately 19 miles, a huge distance relative to the wave
height.
4. The Trough
The trough of a breaking wave is not
the same as that of a deep water wave.
Apparently, as a wave approaches
shallow water the trough
assumes different characteristics, the oscillating wave rising above the
average sea level, see Bascom's Diagram Figure
53 above.
The trough of an individual breaker is
the sum of many complex factors and variation from one wave to the
next may be extreme.
There is some argument as to whether
surfers actually ride the trough of a breaker, see alt.surfing
Post #4 and
others, below.
Bascom's method simply ignores the
variation for individual troughs.
5. Some Surfing Exceptions
a. In point surf,
the reflection of wave energy back from its point of original
contact may cause the wave to peak at maximum height some time
after first breaking.
In some extreme swell conditions at
point surf, the further the surfer rides, the wave gets larger and
the maximum peak should be
measured.
b. In some unusual situations
waves inside the surf zone may combine to produce a lager wave
than those breaking outside, in common surfing terminology, a double-up (huai)
These exceptions should be compensated
for in the following discussion.
SOME PRACTICAL
APPLICATIONS
1. Simple observations
When standing at the waters edge:
- if a set wave is observed to be below
the horizon, for the observer it is under head high.
- if a set wave obscures the horizon,
for the observer it is over head high.
- the further the observer has to move
back and up the beach to align the horizon and the crest, the
larger the waves.
2. Familiarity
Regular use of Bascom's method at
familiar locations means that size estimation becomes learnt.
3. Unknown surfing breaks
The application of Bascom's method is
particularly useful at unfamiliar locations.
4. Photography
Note that surfing photographs are
rarely shot square to the wave face.
If shot from above, the size will be
under estimated, and if shot
from below, as in water shots, the size will be over estimated.
5. Other Wave Variables
All waves of the same height are not
the same.
Each varies in shape, velocity and
power.
a. Wave shape is principally
determined by bottom shape and local wind conditions.
b. Wave velocity, that is the
speed that the wave travels directly towards the beach, is a
product of the strength and duration of the formation winds.
Waves travel between approximately 20
and 40 knots in deep water, slowing
down as they enter shallower water.
Although waves with a faster velocity
are obviously 'faster'; since surfers ideally slide across the
face and not directly to the beach, wave velocity may not be as
crucial as curl speed, or the rate of peel.
c. Wave power, also a product of
the strength and duration of the formation winds, can be estimated
by calculating the period, the time between the arrival of waves
of a set.
For a given height, the longer the wave
period, the more the power of the originating winds and the waves.
AN HISTORICAL
PERSPECTIVE
1. Ancient Polynesia
Although ancient Hawaiian surfers had
many words descriptive of surfing conditions, it does not appear
that they used an empirical form of measurement.
2. The 1900s
Obviously hard to substantiate from
historical records, but all indications are that Duke Kahanamoku
and Tom Blake measured their wave size from the face.
In Duke
kahanamoku's World of Surfing, (1968), Duke recalls surfing at Waikiki in 1930:
The
Bluebirds facing me were easily thirty-plus waves....(page
75, my emphasis)
Tom
Blake's Hawaiian Surfboard (1935)
details the various breaks at Waikiki on pages 62 to 65, indicating their suitable wave sizes.
A photograph between pages 32 and 33, the
famous Kalahuewehe Surf at Waikikii , identifies one wave as
about 30 ft.
All Blake's details correspond to what
would be expected from measuring the wave face.
3. The 1940s
Often the reported quality and heights
of yesterday's waves are exaggerated, a recurring theme exemplified by the common
comment, "You should have been here yesterday!"
Bob Simmons (?) proposed the 2 + 2
Rule, that is:
For
any reported wave size, divide by 2 and add 2 feet.
(My emphasis and I can't find the
reference for this, probably LEGENDARYSURFERS.com)
5. The 1950s
Big wave surfing was boosted with the
development of fibreglassed boards with fins.
Increased interest in wave height saw
Buzzy Trent propose a subjective method - Increments of Fear
6. The 1960s
In Hawaii large wave surfing
accelerates as the focus shifts from Mahaka to Sunset and Waimea on the North Shore -
Jonathan Hoag (alt.surfing Post #40, 1996) contacted several surfers
of the period with impeccable
big wave riding credentials, and
reported the following comments.
George Downing: If you're talking about height use the
"dictionary's definition" of height, "vertical",
i.e.vertical height of the face before it breaks, despite the
fact that there is some addition of height because a wave sucks
out some of the water in the trough.
Ricky Grigg: measure by the
book (oceanography) - the height of the face, trough to crest.
Peter Cole : never has adjusted
his scale downward.
7. The 1970s
In Hawaii, wave size was diminished, essentially cutting the wave face height in
half, largely to intimidate
overseas visitors.
8. Wave Buoys, 1980s
Modern meteorological forecasting
incorporates deep water wave monitoring buoys that provide swell
readings, ostensibly as a support to shipping and as for
protection of land exposed to wave damage.
As deep water wave buoy readings
approximate estimations by the Hawaiian method (that is, from the
back), these readings are often used as 'scientific'
justification.
9. The 1990's
With a resurgence in surf media
attention on big wave riding and the development of tow-in surfing
that put a premium on large wave performance, some surfers around
the world adopted the Hawaiian Method - that wave height
be measured from the back.
Apart from the obvious technical
inaccuracies, this favoured under-estimation as a badge of
bravado.
10. Tow-Ins, 2000
The use of mechanical powered craft to
assist riders to catch waves pushed big wave surfng to new
extremes.
This adrenaline powered approach
resulted in all rational estimations of wave size being ignored.
The mainstream surf media simply
skirted the issue, publishing a series of increasingly
larger ridden waves reported as "bigger than the last ones".
The extent of confusion on the subject
is illustrated in Matt
Warshaw's Mavericks
-
The Story of Big Wave Surfing (2000).
ALTERNATIVE METHODS
1. The "Hawaiian Method"
The "Hawaiian method" proposes that
wave size be measured from the back.
It usually results in an estimation
less than half that of a face measurement.
Coming into use during the 1960's, the
'Hawaiian method apparently was adopted as pyhscological
intimidation of inexperienced visitors, see histoical notes above.
This "method" was reinforced by the
inceased use of wave buoys, whose measuements often equated the
"Hawaiian method".
See below.
It gained some popular use in the
1990's with a resurgence in media attention on big wave riding and
the development of tow-in surfing that put a premium on
performance extremes.
Objections
1. The wave face is the slope
on which a surfer rides and what impedes a surfers' progress out
through the surf.
2. No fixed
reference points.
3. Difficult to confirm by a
second party.
4. Diffifcult to measure a
maximum range - if a wave has a face of 1 foot, how big is
it from the back?
5. Questionable historical
precedent, see above.
6. Favours under-estimation as
a badge of bravado.
2. Wave Buoys
Modern metorlogical forcasting
incorporates deep water wave monitoring buoys that provide swell
readings, ostensibly as a support to shipping as for protection
of land exposed to wave damage.
Objectons
1. Since these measure deep
water waves only, the heights are conservative compared to wave
heights attained before breaking.
2. The more rapid the change
in bottom contour, the greater the difference between swell
height and breaker height.
A given swell height recorded by wave
buoys will produce different size breakers on different bottoms.
3. Wave buoys measure the
oscillating wave, that is crest to trough. A breaker, by
definition, is a collapsing oscillating wave.
4. Apparently (more research
required), breakers rise above the average sea level, see
Bascom's Diagram Figure 53 above.
5. Surfers generally ride the
face of a breaker, crest (muku) to base (honua),
not the trough.
3. The Surfer on the Wave
a. Wave size is calculated by
comparison with the height of the rider by an observer.
Objections
1. Observer must be square to
the wave face
- if they are above, size will be
under estimated.
- if they are below, size will be
over estimated.
2. Surfer's size and stance
vary.
3. Difficult estimating with
prone craft.
4. Becomes inaccurrate at
larger wave sizes.
b. Wave size is calculated by
comparison with the height of the rider by the rider.
Objections
1. Observer is in the least
objective location, and possibly more focused on the factors of
steepness and speed..
2. Surfer's size and stance
vary.
3. Difficult estimating with
prone craft.
4. Becomes extremely
inaccurrate at larger wave sizes.
4. Scale?
a. Feet - Metres - Fathoms -
Cubits?
The traditional surfing measurement
scale has been Imperial (feet), for both waves and surfboards.
With metric standardisation in the
scientific community, wave heights from meteorological sevices
are in metres.
If the measurement is reasonably
accurrate, the scale is unimportant - it can be readily
converted to a familiar one.
For example : 1 metre = approximately
3.25 feet
b. Head-high
A measurement based on rider height,
see Objections 3a. and 3b. above.
REFERENCES
Bascom, Willard: Waves
and Beaches
Anchor Books, New York 1964.
Bascom,
Willard: The Crest of the Wave - Adventures in Oceanography
Harper and Rowe Publishers, New York
1988.
Dixon, Peter L.: Men and Waves : A Treasury
of Surfing
Coward - McCann,
Inc. New York 1966.
Part II: The Science, pages 71 to 90, reprints
the text and diagrams from Bascom's Waves and Beaches
(1964).
Dixon, Peter L.:
The Complete Book of Surfing
Longmans, Green
and Co Ltd., London, 1965, Chapter
4.
Kahanamoku, Duke With Brennan, Joe:
Duke Kahanamoku’s World of Surfing
Angus and
Robertson Publishers Sydney , Australia 1968
Blake, Tom: Hawaiian Surfriders 1935
Mountain and Sea
Publishing, Box 126 Redondo Beach California 90277 1983
Reprint of Hawaiian
Surfboard, Paradise of the Pacific Press, Honolulu, Hawaii
1935
Kuhns, Grant: On Surfing
Charles E. Tuttle
Company. Rutland, Vermont and Tokyo, Japan 1963, Chapter 7.
Klein, H. Arthur: Surfing
J.B.Lippincott
Company, Philadelphia and New York 1965 Chapter H
Kelly, John M: Surf and
Sea
A.S. Barnes and
Co.Inc., New York 1965, Chapter
8.
Farrelly, Midget:
This Surfing Life
Rigby Limited,
James Place, Adelaide 1965, Chapter 4.
Cook, Joseph J.
and Romeika, William J. : Better Surfing for Boys
Kaye and Ward
Ltd., London, 1968, pages 20 - 23
Young, Nat: Nat
Young’s Book of Surfing
A.H. & A.W.
Reed Pty. Ltd., Sydney. 1979, Chapter
8.
Abbott, Rick and
Baker, Mike (Illustations): Start Surfing
Stanely Paul and
Co., London, 1980 , Chapter 4 .
Orbelian, George:
Essential Surfing
Orbelian Arts,
San Francisco,1982, pages 66 - 68
Atkins, Alan (ed)
: The Basics of Surfing
The Australian
Surfriders Association, Victoria, Chapters 1.1 and 1.2
Lowdon, Brian J.
and Lowdon, Margaret (eds.): Competitive Surfing - A
Dedicated Approach
Mouvement
Publications, Victoria, 1988, Chapter
5 Surfing Big Waves (Peter Cole) and Chapter 14
Dynamics of Competitive Beaches (Flynn, Stanford and
Baker).
Finney, Ben and
Houston, James D.: Surfing – A History of the Ancient
Hawaiian Sport
Pomegranate
Books, California, 1996, Appendix A Hawaiian Surfing
Terms, pages 94 - 96
alt.surfing
Dicussion
Board : How do you measure wave size?
http://area51.upsu.plym.ac.uk/~ric/alt.surfing/wavesize.txt
An edited and
annotated copy of this dicussion is included in the Appendix A, below.
Warshaw, Matt: Mavericks – The
Story of Big Wave Surfing
Chronicle Books,
San Francisco, 2000
Bryant, Edward:Tsumami
-
The Underrated Hazard
Cambridge
University Press, United Kingdom, 2001 Chapter 2.
Greg Small (Associated Press): Isle
converts
to global wave measures
Honolulu Star Bulletin Online
Edition Sunday, June 24, 2001
http://starbulletin.com/2001/06/24/news/story10.html
MY RESEARCH
1. After
many years discussing wave size, I came to agree with John
Kelly Jr. who proposed two ways of measuring waves - you can
over estimate or you can under estimate...
John
Kelly on Measuring Wave Heights
Of all the controversies that
surround the surfing community, none burns brighter than the
question, "How big are the waves?" Belligerents divide into
two camps, the underestimators and the overestimators; few
just plain estimators venture into the no man's land between.
Pride, fear, subterfuge, unwarranted honesty, status seeking,
rationalization, poor eyesight, revenge, negligent homicide
and ignorance keep the fires of battle perennially stoked.
At the root of the difficulty are
the awe of the inexperienced and the lack of reciprocal
sympathy by the experienced. Add to this chronic condition,
the differences in perspective between the beach-sitter who
measures distant waves by the space between his thumb and
forefinger, the rider who adds height and speed, and the
unlucky gremlin, carried over the falls on his first try in
big surf, who squares the distance from his eye level to the
trough.
from Kelly :Surf and Sea, 1965. page 222.
2. Kelly
supported his scepticism of scientic calculation by noting that
the scientsts were not out in the surf....
John
Kelly's Objection to Scientific Wave Height
Calculation
Oceanographers
say
the height of a wave is the vertical distance from its crest
to the bottom of the trough. A fine academic definition, but
how many oceanographers are seen out in the surf actually
measuring waves? It's a touchy subject, even for scientists.
from Kelly : Surf and Sea, 1965. page 223.
3. I first encountered Willard Bascom's
method in his autobiography, The Crest of the Wave - Adventures in
Oceanography.
I was not only impressed with the
simplicity of the method, but his dynamic account of surf
surveying circa 1945. These calculations were required
because the scientist was out in large surf, note Kelly's
objection above.
Willard Bascom
: Figure 57 : Surf Surveying , circa 1945
FIG. 57. Surveying in the
surf.
Dukw is overtaken by a breaker
as it moves landward along a course marked by range poles.
Man in Dukw heaves lead and
calls "mark" into radio followed by measured depth.
Transit man on beach reads
angle; an assistant seated by the radio receiver records
both depth and distance.
from Bascom : Waves
and
Beaches, page 40.
Plate 1 : Dukw
surfboarding on twelve foot plunging breaker during a beach
survey (University of California).
from Bascom : Waves
and
Beaches, Plate 1 facing page 68.
4. I
also noted that the method was originally devised in 1945, yet as
far as I knew had never appeared in the mass of surfing literature
produced since then.
I uploaded
Bascom's method to surfresearch.com.au in May 2002.
Text
uploaded to surfresearch.com.au May 2002.
We learned a simple way for a
person on the beach to measure the height of the big breakers,
even though they are far offshore.
Just stand at a level on the
beach where your eyes are exactly aligned with both the high
point of the breaker and the distant horizon; then the
height of the wave is the vertical distance between your
eyes and the backrush.
We would often do that before
risking a run through the surf, but rarely did we do it long
enough to get the highest breakers, because wave heights vary
so much.
We found that about every 3
minutes there would be a series of three higher-than-average
waves.
But sometimes, because the three
highest in one group were not the same height as those in the
next group, we got into trouble. (My emphasis)
Bascom, Willard : The Crest of
the Wave - Adventures in Oceanography
Harper and Rowe Publishers, New York
1988. Page 7
5.
Because there was no accompanying diagram I prepared my own,
also uploaded in May 2002.
Image
uploaded to surfresearch.com.au May 2002- Very poor diagram by Geoff Cater, May
2002
This image supplemented, August 2002,
see 10.below.
6. I
subsequently procured a copy of Willard Bascom's Waves and
Beaches, the text and diagrams providing the foundation
for this article. Concurrently
(and coincdentally) I also accessed Peter Dixon's excellent
anthology, Men and Waves : A Treasury of Surfing, 1966,
that reprints Chapter VII : The Surf of Willard
Bascom"s Waves and Beaches in Part II : The
Science, Pages 71 to 90.
7. In July
2002, searching through google.com I found several
discussion boards on the topic of measuring wave height, one of
which
http://area51.upsu.plym.ac.uk/~ric/alt.surfing/wavesize.txt
contained a spirited and informative discussion.
Some of these
contributions are quoted in the notes above, an edited and
annotated copy of the complete correspondence is included
in Appendix A.
One contributor
offered Willard Bascom's method, but their posting was totally
ignored by the following contributors.
alt.surfing Post #8
szborges@dale.ucdavis.edu (Will Borgeson) Date: 22
May 1996
In case anyone is interested,
here's Willy Bascom's technique for measuring wave height from
shore:
"Simply stand on the beach at
such a level that the tops of the breakers are exactly in line
with your eye and the horizon. The vertical distance between
your eye and the 'backrush curl' (upper edge of water on
the beach) is equal to the height of the breaker."
Quoted from Bascom : Waves and
Beaches, 1964.
The text in bold added by Will
Borgeson to explain the difficult concept of "backrush curl".
So, if you're 6'tall and there's
about 12' of height between the top of your head and thewater
line, you're looking at 12' faces. This technique can be
useful if there's no one out, the surf looks pretty big, but
is way out there and hard to judge.
Will
NOTE : Apparently no-one was
interested, this method was subsequently ignored by all
further postings.
8. google.com also turned up an article
featured at the Honolulu
Star
Bulletin Online Edition Sunday, June 24, 2001 by Greg
Small
(Associated Press) entitled Isle
converts to global wave measures : Wave heights taken
from the front go against the traditional method of measure that
reports The wave reporting system changed in April , when the
weather service finally convinced observers to report the
full-face value of waves. The text of this article is
included in Appendix B, below.
9. Initial
research readily identified the discrepancy between measuring
deep water waves and measuring breakers, however an
understanding of breaking waves mechanics rquires further
research. Bascom's Figure 15 illustrates some of the
internal forces.
Willard Bascom
: FIG. 15 Breaking wave forces
FIG. 15. The movement of
a wave as it breaks in a wave channel (from motion picture
analysis)
from Bascom : Waves
and
Beaches, page 40.
10.Supplementary
Image,
August 2002.
Goodvibes Surf Check circa
1973, after Bascom/Edwards.
Digital manipulation by
surfresearch.com.au, 2002.
11. After
copying and editing the alt.surfing discussion and
further research, this page was uploaded to surfresearch.com.au
in August 2002.
APPENDIX
Copyright Note : The pages below are
reproduced here because of the lack of an archival tradition by
online media and changes in location fail to guarantee future
access. Anyone who wishes their contributions removed, please
conact the editor.
Appendix A
: Edited
Postings
from Newsgroups : alt.surfing
http://area51.upsu.plym.ac.uk/~ric/alt.surfing/wavesize.txt
Subject : How do you JUDGE WAVE
SIZE?
Editing, highlighting in bold and
additional
text in italics, by Geoff Cater, July 2002.
Post #1 jona@aloha.net (jona
) Date: Sat, 11 May 1996
I hear lots of different methods of
judging wave size.
I'm going to take a survey - check the
one you believe is correct; one answer only.
(We all know what is supposed to be the
correct way, right?)
Method
1. face of the wave just
before it breaks
2. some portion of the
face of the wave before it breaks
3. open ocean deep water
swell size
4. back of the wave
Scale
consensus (I heard others say it was
___ feet)
conservative (in Hawaii this would be
____ feet)
local standards (in our locality it
would be ___ feet)
double (or whatever) overhead
Post #2 mesa2@ix.netcom.com
(Rick Ciaccio) Date: 11 May 1996
Around here (?) the general
consensus is:
4 foot swell reported meansoverhead
surf;
6 foot swell means double overhead;
6 foot S (Simpson Scale?) Wedge
swell means triple overhead+ :-)
We judge 'em from trough to lip with
a surfer on it, we always refer towave size by face.
We always refer to Wedge wave size by
"Simpson Scale" -
Fred (Simpson?)'s (of Viper
Fins) own interpetation which has become the standard,
much like the illogical Hawiian way
of calling them.
Generally, we reduce it to "good",
"fun", "pounding", or "slamming",
that pretty much says go out.
When posting in alt.surfing I call
them in face size from trough to lip
as they pitch (honest).
Rick
Post #3 Ric@diltd.demon.co.uk (Ric
Harwood) Date: Sun, 12 May 1996
Interesting question as there are
surfers from all parts of the world here.
some portion of the face of the wave
before it breaks
Top 2/3 as seen from the beach.
This eliminates the run out in front
of the face as it is not steep enough to derive any power off,
but still looks like "height" from
the front.
Ric
<irl://thereis.nothing.that.agood/days/surfing/can't/cure.exe>
PGP: 0766ABE5 | Homepage
http://area51.upsu.plym.ac.uk/~ric/
Post #4
tbmaddux@alumnae.caltech.edu (Timothy B. Maddux)
Date: 14 May 1996
In direct comment on Post #3 ...
What about when you're surfing those
gnarly suckout reefs
where the aforementioned "run out" is
actually a steep
concaving below-sea-level nightmare?
Poses the question : To measure or
not to measure the trough?
Tim Maddux --
tbmaddux@engineering.ucsb.edu
Santa Barbara Surfing --
http://www.engineering.ucsb.edu/~tbmaddux/
Post #5 Ric@diltd.demon.co.uk (Ric
Harwood) Date: Thu, 16 May 1996
Reply to Post #4...
I wouldn't know, [as I'm suffering from
a sucking reef defiency {:^( ] - humour
How would you measure these?
Ric
<irl://thereis.nothing.that.agood/days/surfing/can't/cure.exe>
PGP: 0766ABE5 | Homepage
http://area51.upsu.plym.ac.uk/~ric/
Post #6 OceanRider
<oceanrider@prtcl.com> Date: Sat, 18 May 1996
Humour...
Hey I've got a great idea!!!
All of you sit on the beach and figure
out how big the waves are, while I go surfing!
My favorite surfer is the one sitting
on the beach anyway!
Happy figuring, Glenn
Post #7
tbmaddux@alumnae.caltech.edu (Timothy B. Maddux) Date: 19
May 1996
In reply to Post #5, the question
about measuring the trough (a concaving below-sea-level
nightmare), humorous...
1. From the beach at a
safe distance away, or
2. by having a friend
photograph me as I get pitched over the falls,
then using my outstretched 6' frame to
accurately measure the wave heights.
3.The amount of my body
sticking straight up out of the water upon impact
into the sand or reef could also be
easily used to determine the depth of
water at breaking as well.
Tim Maddux --
tbmaddux@engineering.ucsb.edu
Santa Barbara Surfing --
http://www.engineering.ucsb.edu/~tbmaddux/
Post #8
szborges@dale.ucdavis.edu (Will Borgeson) Date: 22
May 1996
In case anyone is interested, here's
Willy Bascom's technique for measuring wave height from shore:
"Simply stand on the beach at such a
level that the tops of the breakers are exactly in line with
your eye and the horizon. The vertical distance between your eye
and the 'backrush curl' (upper edge of water on the beach)
is equal to the height of the breaker."
Quoted from Bascom : Waves and
Beaches, 1964.
The bold added by Will Borgeson to
explain the difficult concept of "backrush curl".
So, if you're 6'tall and there's
about 12' of height between the top of your head and thewater
line, you're looking at 12' faces. This technique can be useful
if there's no one out, the surf looks pretty big, but is way out
there and hard to judge.
Will
NOTE : Apparently no-one was
interested, this method was subsequently ignored by all
further postings.
Post #9 mundaka@acca.nmsu.edu
(mundaka) Date: 13 May 1996
Double or whatever overhead. (Kinda
hard to judge feet anyway.)
---No hay pedo!---
Post #10 "N. Briggs" <briggsn>
Date: 16 May 1996 02:17:08 GMT
Seems to me that if you estimate the
wave size in proper feet (the ones used on land) then half if,
you're getting close.
Post #11 jritchie@iafrica.com Date:
Tue, 14 May 1996 21:36:51 -0700
Here in Cape Town we also have these
arguments.
Lank (?) of my friends judge
from the front, but where I come from (Victoria Bay) it was judged
at the back.
I'm so used to
6 feet being way overhead (
1 foot being knee-height,
2 feet being waist to chest height,
3 feet being chest to head height,
4 feet justover head height,
5 feet being overhead)
that when my friends tell me a size,
it's completely different (usually smaller) than what I
imagined...
Craig
Post #12
graham@big-g.win-uk.net (Graham Harrop) Date: Wed, 15 May 1996
I'd say(2) "some portion of the face of
the wave before it breaks"
and like Ric (Post #3 ) and
Craig (Post #11), it's about 2/3rds of the shoulder.
To me, a 4 foot wave is a 6' face. Set
waves (say best of six), not the average.
Predicting waves is my job and I'm
amazed at the lack of consensus on wave heights.
If we used Hawaiian scales here in
the UK it'd be inches, not feet.
And then there's the French who use
something called "metres".
As long as we're consistent, we'll
understand each other.
Maybe it'd be better to say
"shoulder-hopping", "head high", "overhead" or "double
overhead". - The head-high scale
Good thread, Graham
Big G.
graham@big-g.win-uk.net
Post #13 Ric@diltd.demon.co.uk (Ric
Harwood) Date: Thu, 16 May 1996
20:27:07 GMT
In direct reply to Post #12, an
objection to using a Head-high scale...
I'm liking this more and more.
But then I chat to my knee board friend
and we have to convert in and out of feet again 'cos he keeps
talking about these shoulder high "overhead" waves!
Ric
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Post #14 graham@big-g.win-uk.net
(Graham Harrop) Date: Fri, 17 May 1996 12:19:38 GMT
Direct reponse to post #13...
Oooh, you bitch, Mail bomb on the way,
Graham.
Assumption : Graham is 'the
knee board friend' in Post #13
Post #15 Ric@diltd.demon.co.uk (Ric
Harwood) Date: Tue, 21 May 1996
Direct reponse to post #14...
Not at all. *he's* the lucky one who
hets to surf overheads all the time!
Ric
<irl://thereis.nothing.that.agood/days/surfing/can't/cure.exe>
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Post #15 salmonm@batis.bis.und.ac.za
(MR Salmon) Date: 23 May 1996 08:53:03 GMT
Direct reponse to Post #12 and Post
#13 on the Head-high scale...
Who really gives a shit?
The only people who you should be able
to relate to are your friends
- as long as you say a 6 foot wave and
they know hwat you're talking about, then you're fine.
Judging wave size is never gonna be
consistent world-wide, so who cares?
MATT
From: njtravis@cse.lbl.gov (Nancy
Jean Travis) Date: 23 May 1996
Reponse to Post #15 ...
Now I like calling them small.
If I say it was 3 foot, my friends
understand it was pretty hot.
I remember a Billabong Pro at the Lane
when Munga (Barry) took a barrell as big as the cliff and
the announcer called it 12.
F#$k, I thought, its 25 easy.
I remember it intimidated me horribly.
On another day at Sewers which I would
have called 15 foot, Moth was screaming its a perfect 5!
I couldnt even get out the back that
day.
Now I just cut the face in half and
subtract a foot.
This really irks people who have an
attachment to reality which is even more amusing.
So yeah, the day I surfed North Point
in Cowaramup it was a lovely six feet, double overhead bombs. B-).
The wave I broke my board on was asolid
3 foot, hahaha.
fang
Post #17 the Sandman
<whammer@whammer.com> Date: Thu, 23 May 1996
Direct reponse to Post #15 and Post
#16
we've alot of kooks round here that
have to plug the actual wave size in a function() ;-) to get the
the wave size that they'll
tell you.
For the life of me I don't understand
it.
I guess my life is complicated enough
not to add another layer to it.
What I see is this; I'm surfing in
double-0 conditions and they're on the beach debating wave height.
Kooks unite and hash out a standard.
When your done, paddle out and let me
know...if ya can
the Sandman
http://www.whammer.com
Odds are, you're probably a kook
Post #18
leepadr@coastalnet.com (Lee Padrick)Date: 17 May 1996
Response to Post #11
I agree for the most part with your
size descriptions.
I'm from North Carolina, stand 6' 3"
tall and usually call a chest-high wave about 3 feet.
I usually amused by shorter guy (or
girls) who call chest-high 5 feet (or larger).
But then again, if you get pitched by
an 8-foot peak, you're gonna fall 8 feet!
Lee Padrick
<leepadr@coastalnet.com>
Post #19 Einstein
<einstein@mars.superlink.net>Date: Wed, 22 May 1996
Resoponse to Post #18
Dude I am 5'10" and learned a three
feet wave is over my head from the inside.
"Imagination is more important than
knowledge!"
Einstein
mailto:einstein@mars.superlink.net
http://mars.superlink.net/einstein
netscape 2.0 or better
http://mars.superlink.net/einstein/einstein.html
others
Post #20 JIMSLADE@msn.com
(James ) Date: 20 May 96
Who cares? If it swells, ride it!
I've been listening to this shit for
years and it doesn't matter how you measure a wave, its how you
surf it!
If your not sure just look at it and
make up a good lie like everyone else!
Post #21
robt2@ix.netcom.com(robert brannan ) Date: 20 May 1996 05:03:18
GMT
All wave size judgement is correct for
your locale, it more reflects the consistency and size range for
your area.
We measure reams of cloth in yards,
height of men in feet, cigarette length in millimeters.
However for waves, we all use feet, but
each geographic locale has a different consistency and size range,
-- thus we change or stretchor shorten
our rulers.
It gives us all a better feel for the
variability of size that exitsts at our own breaks.
I've seen some winter's so consistent
with new 4-6'swells every 3-4 days and bigger, that when I pass a
friend and ask for a report and viceaversa, we would just reply
" It was good, it will be good
tomorrow" or "It was good, it will be smaller tomorrow"
Post #22 gjohnson@dream.season.com
(Reality is a point of view) Date: 20 May 1996
Reponse to Post #21
I've heard a similar suggestion for
call/fax/net surf reports.
Gary Johnson "There's no union called
the AFL-CIA is there?"
gjohnson@season.com <a
href="http://www.efm.org">Walk The Talk</a>
CAMPAIGN '96: Juck 'em if they can't
fake a toke.
Post #23
sponge@news.ohana.com (Neal Miyake) Date: 15 May 1996
In Hawaii, we "measure from the back,"
meaning, we essentially cut the wave face height in half.
The reason (I think) is because of
Californians in the 50s and 60s sandbagging to surprise newcomers
to the islands.
I know it's stupid, but it's the
standard that everyone uses.
Nowadays, if you don't call it like the
locals do, you'll be put down bigtime.
The local media, especially the radio,
perpetuate the underestimating.
So, three feet is head high, six is
double overhead.
Don't even ask what twenty-five is.
When I was working at the Eddie in 89,
I asked the judging panel how big they thought it was.
There was a long silence before someone
(I thinkJack Shipley) said, "Overhead!"
I guess only Ken Bradshaw is allowed to
make the call at Waimea.
Interesting personal observation: a six
foot wave in the Country is bigger than a six foot wave in Town.
sponge
P.S. Right now, Town is one-to-two
feet.
Post #24 surffohio@aol.com
(SurffOhio) Date: 15 May 1996
Response to Post #23
Apparently the reason is due to
scientific fact. See below.
Today my daughter got her Exploring The
Ocean book from World Book.
They had a chapter called Wave Makers.
The following is an excerpt.
"The height of a wave is measured
from its crest to its trough.
The crest is the wave's highest part
or peak.
The trough is the lowest part, the
depression the wave makes in the water's surface."
This is the correcct method of
measuring deep water waves only - and is not applicable to
breakers.
The picture illustrated the trough as
being the depression between two waves, not the face before it
closes out on the beach.
So, with the above data the Hawaiians
and World Book are in full agreement.
I am glad. I don't want to see my 10
year old get confused. :-)
This does bring up a question.
If one is riding 25 ft Waimea is he
dropping down a 50 to 75 foot face?
Or, is the face height used since it
would sound much more significant than a 10 to 12 footer?
If I dropped down a 25 ft face at
Waimea, I would at least feel like I had ridden a 25 ft wave
(after I had gotten done peeing all
over myself).
Sorry Rick C., I guess you've been
getting pounded by 3 footers at thWedge all this time. :-)
I want my damn money back for all
those pics yousold me of the Wedge!!!!
Ok...........just kiddin.
Surff
Post #25 Ric@diltd.demon.co.uk (Ric
Harwood) Date: Thu, 16 May 1996
Response to Post #23 and #24
Sure. If this were sci.geo.ceanography
the waves are described by these characteristics:
L= Wavelength, [peak to peak, trough to
trough...]
C= speed, [don't let's get started on
that one.]
T= period, [time for one L to pass a
point, or time between zero upcrossing periods.]
H=Height [Vertical height between
bottom of trough and top of peak.]
Again, this is the correcct
method of measuring deep water waves only - and is not
applicable to breakers.
a= Amplitude [Displacement from Mean
Sea Level, (H/2) ]
Steepness = [ H/L ]
k= wave number [ 2pi/L]
and a few other more obscure ones.
When you look at the face of a wave
from the beach you see H.
However you will usually see a surfer
playing on just the top 2/3 of this H because the bottom 1/3
tends to not be steep enough to surf, even on a steep wave. (Common,
but not always correct)
Perhaps this is rather different on
very abrupt reef edge breaks.
I'd be interested to see a
description from those with more experience of these than I do.
[that must include a lot of
you,because I don't have any yet... {:^( ]
ATB
Ric
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Post #26 mesa2@ix.netcom.com(Rick
Ciaccio) Date: 17 May 1996
Doesn't every clique or group have
their unwritten or unspoken way of communicating?
We use words like "pound" and "slam",
or at the other end of the scale "queenie".
When you include the word "pound" in
your sentence why do you need to measure it?
Rick
Post #27
tbmaddux@alumnae.caltech.edu (Timothy B. Maddux) Date: 17 May
1996
Reponse to Post #24, Measuring deep
water waves = The Hawaiian method...
[ rant mode on ]
Actually, they are not in agreement.
Wave height as the World Book defines
it it is precisely the distance from the top of the crest to the
bottom of the trough.
So, a breaking wave's height would be
the distance from the top of the crest to the bottom of the
trough,
at the exact moment when the wave
*just* begins to break, or when the water particle velocity at the
crest is equal to the wave's phase speed , and the lip just starts
throwing out.
To put it another way, the "height"
of a wave is always defined in the same manner, be it a breaking
wave, shallow water wave, or deep water wave.(not necessarily
correct, shallow water waves of tanslation do not have a
trough.)
If you had a wavewire out in a
Hawaiian break, under monochromatic wave conditions (all the
same height and period), the wire would record exactly the same
difference in water surface elevation from the crest of the wave
to the trough in front as it breaks as the difference from that
breaking elevation to the trough after it passes by, i.e. the
backside.
The only way to get away with
describing a measurement as "from the back" and actually MAKING
such a measurement is by doing so on a very shallow water reef
surrounded by open-ocean depth water.
Each wave crest could approach and
shoal and break while the following trough and crest behind it
were still at their deep water values and essentially
negligible.
Then the distance from trough behind
to breaking crest would approximately be half that of the
breaking wave in front.
Hawaiian reefs, however, shoal up
more gradually than this, as evidenced by many photos in the
mags of lines of black walls to the horizon.
[ rant mode off ]
They're not measuring from the back,
they're just dividing the actual breaking height by 2.
Quoted from Post #24 :
"This does bring up a question. If
one is riding 25 ft Waimea is he dropping down a 50 to 75 foot
face?"
Answer : Roughly 50 feet, yes.
Tim Maddux --
tbmaddux@engineering.ucsb.edu
Santa Barbara Surfing --
http://www.engineering.ucsb.edu/~tbmaddux/
Post #28 dfrick@lava.net (Doug
Frick) Date: Fri, 17 May 1996
Reponse to Post #27, Quotes and
answers...
Quote from Post #24 :
"Hawaiian reefs, however, shoal up more
gradually than this, as evidenced by many photos in the mags of
lines of black walls to the horizon."
Answer :
Another possibility is that those black
walls are essentially open-ocean waves.
Quote from Post #24 :
"They're not measuring from the back,
they're just dividing the actual breaking height by 2."
Answer :
Well, theory aside, I do measure from
the back.
When I see a surfer kick out and the
backside that he's coming down on is twice his height, that's
about a twelve foot wave.
If you watch the next set come in from
the front, the wave is probably four times the surfer's height
from top to his bottom turn;
that's twenty-some feet.
After a few years of guessing wave
heights and getting agreement (or ridicule) from the bruddahs, you
know what the local standards are. (They do vary on different
parts of Oahu.)
I'm not disputing your definition
of (deep water) wave height (at least it's
consistent) or the behavior of monochromatic waves. Theory's good
for wave tanks.
Quote from Post #24 :
"This does bring up a question. If one
is riding 25 ft Waimea is he dropping down a 50 to 75 foot face?
Roughly 50 feet, yes."
Answer :
Agreed.
Doug Frick
dfrick@hcc.hawaii.edu
dfrick@lava.net
Post #29 Ric@diltd.demon.co.uk (Ric
Harwood) Date: Sun, 19 May 1996
Response to post #28
In alt.surfing, dfrick@lava.net (Doug
Frick), Doug Frick wrote:
Quote from Post #28 : "Another
possibility is that those black walls are essentially open-ocean
waves."
Not really AFAIK, the ocean swell
waves [deep water, depth>(L/2) will have a height of a couple
of meters or so and a length of the order of a couple of hundred
meters.
Wave looking steep and dark are
generaly feeling the bottom.
Ric
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Post #30
tbmaddux@alumnae.caltech.edu (Timothy B. Maddux) Date: 19 May
1996
Another response to post #28
Quote from Post #28
"Another possibility is that those
black walls are essentially open-ocean waves."
Reponse :
Open-ocean waves are exemplified by
incredibly low steepness... a 10 ft. 20 s. wave has an open-ocean
wavelength of gT/2pi = 31 m, which means the 3 m of height
difference is spread out over 15 m, not much of a wall.
Quote from Post #28
"Well, theory aside, I do measure from
the back. When I see a surfer kick out and the backside that he's
coming down on is twice his height, that's about a twelve foot
wave."
Reponse :
Ah, but you're not waiting long
enough... if you wait for him to get ALL the way down the back,
which would be in the trough of the approaching wave as it begins
to throw, then the backside and front side would appear about the
same.
Once a wave starts to break, its
carried energy starts to dissipate, which is seen in a reduction
of the wave's height.
So if you watch the backside of the
wave as he floats down it, you'll notice that it's decreasing as
it moves shoreward.
Quote from Post #28
After a few years of guessing wave
heights and getting agreement (or ridicule) from the bruddahs, you
know what the local standards are. (They do vary on different
parts of Oahu.)
Reponse :
As my surf reports show, I just use
face-of-wave estimates based on human proportions (v.s. a 6' tall
person). It's my understanding that this is still o.k. in the
Islands, i.e. a 3' Hawaiian wave or 6' Cali wave are both about
head-high... right?
Tim Maddux --
tbmaddux@engineering.ucsb.edu
Santa Barbara Surfing --
http://www.engineering.ucsb.edu/~tbmaddux/
Post #31
carley@manly.civeng.unsw.edu.au (James Carley) Date: Mon, 20 May
1996
Response to Post #30
Quote from Post #30
"Open-ocean waves are exemplified by
incredibly low steepness... a 10 ft. 20 s. wave has an open-ocean
wavelength of gT/2pi = 31 m, which means the 3 m of height
difference is spread out over 15 m, not much of a wall."
Response :
Sorry to be a smartarse Tim but your
theory is a bit wrong.
Deepwater wavelength should be
L= gT^2/2pi
or L = 1.56 T^2 where T is wave
period
which for your 20 s period wave
gives L = 624 m
or more realistically T = 15 s gives
L = 351 m
Someone else wrote: (Quote from
Post #28)
"After a few years of guessing wave
heights and getting agreement (or ridicule) from the bruddahs,
you know what the local standards are. (They do vary on
different parts of Oahu.)"
Response :
This describes the macho height
system well, it's all about peer group acceptance rather than
science.
Do they call their 9' board a 4'6"?
I'm another who measures waves
scientifically as part of my job.
In real terms this means that a head
high breaking wave is ~6 feet.
When discussing with pseudo machos I
use the HEAD scale or sometimes to confound them (and in my own
reference scale)
I say an X metre face 'cause metric
is the future.
James Carley
Water Research Laboratory
University of New South Wales
Sydney, Australia
James Carley
Sydney, Australia
carley@manly.civeng.unsw.edu.au
Post #31 dfrick@lava.net (Doug
Frick) Date: Mon, 20 May 1996
Reponse to Post #30
The topic of this thread is "How do you
JUDGE WAVE SIZE?"
You judge it scientifically. That's
nice.
But if you come to Hawaii and say you
ride fifty-foot waves, nobody is going to believe you.
Thescientific measure you're using is
nothing more than a method accepted by your 'science' peer group.
I'm not saying there isn't astandard
scientific measure, it just isn't the one used where I surf.
(And I made that disclaimer in my
post.)
My 9'6" is 9'6", as agreed upon by
my peer group of measuring tape owners.
Doug Frick
dfrick@hcc.hawaii.edu
dfrick@lava.net
Post #32
tbmaddux@alumnae.caltech.edu (Timothy B. Maddux) Date: 24 May
1996
Response to post #31
Would they believe me if I called a
double-overhead wave as 6 feet, assuming everyone accepts that the
wave really is double-overhead on the face?
Most people in the area where I surf
use "faces" and "backs" to make the distinction between
full-sizing and half-sizing
the wave heights. There's usually
very wide scatter in the assessment of wave heights, most easily
judged from land and
most adrenaline-elevated when ducking
them.
I have my own bias when making
reports, I won't typically report the larger heights of set
waves unless I either surf
a few myself or get pounded by them
in a noteworthy fashion.
Otherwise it just doesn't count.
Tim Maddux --
tbmaddux@engineering.ucsb.edu
Santa Barbara Surfing --
http://www.engineering.ucsb.edu/~tbmaddux/
Post #33 dfrick@lava.net (Doug
Frick) Date: Mon, 20 May 1996
Response to Post #30
Quote from Post #30
"Open-ocean waves are exemplified by
incredibly low steepness... a 10 ft. 20 s. wave has an open-ocean
wavelength of gT/2pi = 31 m, which means the 3 m of height
difference is spread out over 15 m, not much of a wall."
Response
Yeah, I saw I was wrong on that one
after I went and looked in my ocean textbooks.
On big north swell days at Makaha, you
can watch the sets going by on the horizon, perpendicular to shore
(Makaha faces west), as well as watching the (wrapped) sets coming
straight in.
Quote from Post #28, re-quoted in
Post #30
"Well, theory aside, I do measure from
the back. When I see a surfer kick out and the backside that he's
coming down on is twice his height, that's about a twelve foot
wave."
Quoted response from Post #30
Ah, but you're not waiting long
enough... if you wait for him to get ALL the way down the back,
which would be in the trough of the approaching wave as it begins
to throw, then the backside and front side would appea about the
same.
Response
Yes, that is true. I'm not waiting
twenty or so seconds to make my guesstimate (and believe me, I'll
be about ten feet under the water when that next wave pitches).
But that's my point. I'm not attempting to duplicate the
scientific measure here. The method I use yields an answer
consistent with the local description of wave size, which is what
I'm trying to achieve.
Quoted from Post #30
As my surf reports show, I just use
face-of-wave estimates based on human proportions (v.s. a 6' tall
person). It's my understanding that this is still o.k. in the
Islands, i.e. a 3' Hawaiian wave or 6' Cali wave are both about
head-high... right?
Response
That's usually correct, and if you say
"head-high" (as opposed to 6')people will know what you mean.
I'll stick my neck out here, and
call a wave.
I have a picture of me out
bodysurfing: http://www.lava.net/~dfrick/mz-1.jpg .
Slapping a ruler up on my monitor
yields a face height of about 4 inches.
From my head to my outstretched hand
is about 1/2 inch = 3 feet.
So I'd guess the face height is about
24' (do people actually say "quadruple overhead"?).
From my memory, I'd call this wave
about a 10-footer, on a 12'+ day.
What matters most is that people
know what the other person means, whether backs, faces, heads,
or scientific.
When I quote Hawaii waves, I usually
put (backs) after the height.
When I go to the Washington coast, I
switch to quoting face sizes.
When I look in the databases, I
expect scientific measure.
They all have their place.
Doug Frick
dfrick@hcc.hawaii.edu
dfrick@lava.net
Post #34: ric@diltd.demon.co.uk (Ric
Harwood) Date: Wed, 22 May 1996
Response to Post # 33
Quote from Post #33
"What matters most is that people know
what the other person means, whether backs, faces, heads, or
scientific.
When I quote Hawaii waves, I usually
put (backs) after the height.
When I go to the Washington coast, I
switch to quoting face sizes.
When I look in the databases, I expect
scientific measure. They all have their place."
Response
That's exactly it IMHO.
I the scientific context we would use
meters, peak to trough, but at the beach that is meaningless in
that everyone else there is using different 'scale', and each area
has it's own scale. [almost but notquite entirely unlike feet].
Which is why jona started the thread in
the first place.
The interesting/confusing thing here
in alt.surfing is that there are people reading and posting from
all these different places, so
it takes is hard to get the hang of
what everyone means by "x foot", especially as many of us have
not yet had the opportunity of surfing the world and knowing the
length of the local ruler.
[Indeed the pleasure of a.s is being
in touch with people who areout getting stoked all over the
world]
Certainly the body sized ruler seems
to the thing to use.
We all know how big out local "feet"
are, and most of us will be within a couple of 'heads' of 6'
tall.
Good thread Jona, thanks.
Ric
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Post #35 tdstearns@aol.com
(TDStearns) Date: 18 May 1996
its pretty clear that feet and meters
arent too great...changes from spot to spot and even wave to wave
make "actual" size difficult to discuss..even if you count the
back or the front.. youre going to get waves that come from a
similar swell size and look totally different as theyre
breaking...
maybe..as an earlier post said..the
best way for surfers to deal with this (as opposed to the method
from sci.geo.oceanography)..is just knee high..butt high...waist
high..nipple high..etc..a 4 foot wave here is different from a 4
foot wave there..but if i say head high..you know about what im
talking about...
i gave up using
numbers......although i have few short friends who get a
little confused
sometimes..."head-high?"
Toby - Oregon
No surf here, try WA
Post #35 dagum@barrel.asd.sgi.com
(Leo Dagum) Date: 20 May 1996
It's all relative right?
If I'm out with a buddy and the waves
are of any consequence, then we down play them.
Nothing is ever more than 'solid
overhead' (even if they're 15' faces).
Or if one of them comes through a
little mushy then we'll say "they're shouldering up a bit today",
even though you just saw two perfect A-frames go by.
Maybe it's machismo but personally I
think it's just an effective way of dealing with fear.
I'd rather delude myself by playing
these games than admit the waves really are big and scary and end
up paddling in (or worse yet, freezing up at the wrong moment and
getting axed by one of those that didn't "shoulder up").
Of course if your buddies aren't
around, then it's always "double overhead and hollow, you really
MISSED it dude!"
But it's just games we play because if
we really want to describe the surf we'll just rattle off the buoy
readings for backup "10'/14sec from 285...SOLID overhead".
- leo
Leo Dagum
Supercomputer Applications Tel:
415-933-2179
Silicon Graphics, Inc. Fax:
415-933-3562
Mountain View, CA 94043 email:
dagum@sgi.com
Post #36 surffohio@aol.com (SurffOhio) Date:
20 May 1996
Reponse to Post #27
Quote from Post 27
"So, with the above data the Hawaiians
and World Book are in full agreement.
[ rant mode on ]
Actually, they are not in agreement.
Wave height as the World Book defines it it is precisely the
distance from the top of the crest to the bottom of the trough.
So, a breaking wave's height would be the distance from the top of
the crest to the bottom of the trough, at the exact moment when
the wave *just* begins to break, or when the water particle
velocity at the crest is equal to the wave's phase speed , and the
lip just starts throwing out."
Response
....snipped the rest because I dont
understand it and I started to feel dumb....
Jee whiz, my daughter and I just liked
the cute picture in World Book about waves. :-)
Surff
Post #37 Einstein
<einstein@mars.superlink.net> Date: Wed, 22 May 1996
I think the thickness of a wave plays
an equally big part.
Like a wave of the same height in
Hawaii is much better than the same sized one in NJ most of the
time.
Its much more powerful and hollow!
Extended Quotes from Post #23 and
Post #24
"Imagination is more important than
knowledge!"
Einstein
mailto:einstein@mars.superlink.net
http://mars.superlink.net/einstein
netscape 2.0 or better
http://mars.superlink.net/einstein/einstein.html
others
Post #38 Sgulie@ix.netcom.com
(Steven Gulie) Date: Fri, 17 May 1996
Interestingly, the bouys that measure
wave height, in ft or meters, don't bob up and down the height of
the wave (they don't look over the edge and get scared, either).
They estimate the wave size by the
angular momentum imparted when the wave passes under the tethered
bouy.
This is a little like judging the size
of a wave by how hard it rings your bell when it slaps you upside
the head...
So that's how I measure it. Ow! Big
one!
When I'm watching from the cliffs, I
estimate wave height by the face *with a rider on the wave*.
If he's cruising down the line, and
the lip is above his head, it's *overhead*.
This discounts the trough, since the
rider is on the face.
If it's a sponger (prone rider),
you can still guage it pretty well, since he's stretched out
full length on the wave, and you can see
how high it is relative to a person's
length.
A hollow wave is bigger than a
crumbling wave of equal height. Huh? No, I mean it.
A wave pitches out because the bottom
has gotten shallow so suddenly that it can't reach its full
height.
A given reef can only take a wave of
a certain size.
Any bigger and it either breaks on a
deeper reef outside, or it buckles in the middle before it can
even pitch out (weird
looking, when it happens).
Bizarre side waves like the Wedge
defy this logic.
So much energy is running sideways
and backwards up the beach that it's more like a waterspout than
a wave in the classic physics model:
it does whatever the hell it wants
to, including lurching 25' into the air when it's only 2'deep.
A question for da macho boyz who
measure it "from the back": You saw it from the back? Why didn't
you go?
Steve Gulie (sgulie@ix.netcom.com)
\... Wilbur would go...
Post # 39 Einstein
<einstein@mars.superlink.net> Date: Wed, 22 May 1996
"Imagination is more important than
knowledge!"
Einstein
mailto:einstein@mars.superlink.net
http://mars.superlink.net/einstein
netscape 2.0 or better
http://mars.superlink.net/einstein/einstein.html
others
Post #40
jona@aloha.net (jona) Date: Tue, 28 May 1996
Conclusion by the author of Post
#1
Thanks for the many replies this thread
has elicited - lot's of good responses.
First, the answer: surf height is
measured on the wave's face, from the trough to the crest.
Yes, I know that's just a textbook
definition.
First point, the BIG GUNS.
I spoke with George Downing, one of
the first inductees into Surfing's Hall of Fame here in Hawaii.
He makes the call on when to hold the
Eddie Aikau Quicksilver Waimea big wave contest, minimum 20 ft
required for this contest.
George said, if you're talking about
height use the "dictionary's definition" of height, "vertical",
i.e.
vertical height of the face before it
breaks, despite the fact that there is some addition of height
because a wave sucks out some of the water in the trough.
I also spoke with Rick Grigg,
oceanographer and long time big wavsurfer.
His answer was measure by the book
(oceanography) - the height of the face, trough to crest.
He also brought up the interesting
point of the psychology of judging wave height.
The "correct" measurement will assure
acceptance/approval among other surfers (you're "in"); someone
who doesn't know how to measure correctly is "out".
The idea of group identification is
in itself another very interesting topic (new thread? maybe too
much analysis; we surf because it's fun).
Another surfing great disagreed,
however. Rabbit Kekai told me the height is measured from the
back of the wave.
Second, artificial DISTORTION of
what's plain.
Mark Cunningham, lifeguard at Ehukai
Beach Park (Pipeline) admitted that surfers may have gotten
jaded due to their familiarity with waves of all sizes.
This was in response to my claim that
presently wave heights are underestimated compared to what we
judged waves to be
around 20 years ago.
I lived and surfed on the North Shore
of Oahu back then and it seemed people had some consensus about
judging size.
(I still surf now too)
Another well-known big (or small)
wave surfer, James Jones, said big waves are underestimated.
He said when it reaches 20 ft or more
"all objectivity goes out the window".
George Mason, meteorologist and
professional surf forecaster for Wave Track/Surfline said it's
"like beating your head against the wall" in describing his
efforts to persuade people that the correct measurement is the
face of the wave.
In fact, the surf forecast from Wave
Track/Surfline will mention "head high", etc. to escape the
problem of varying scales of wave measurement.
Through George's efforts one of the
daily newspapers prints the definition, height measured from
trough to crest, under the daily surf forecast.
CONCLUSION - are we CONFUSED?
I have to admit that there is a good
number of surfers here in Hawaii who believe the back of the
wave is the height of the surf. The big problem with this is
that is the back of the wave has a very gradual slope which
makes estimating height very difficult, plus you can't see it
from the land.
Anyway, replies to my thread reflect
this confusion: changing judgement when in another locality,
peer group scale, using a
body-size scale, reducing the face
size by a factor. I contend the back of the wave measurement is
also a reflection of a
too-conservative measurement.
Not only are surfers misled, the
surf forecasters are influenced.
I am a meteorologist/forecaster for
the National Weather Service in Honolulu (a neat job for which I
thank the Lord).
I spoke against the back-of-the-wave
measurement misconception with some of the forecasters here.
Even though they know what the book
says - they were told by some of the surfers and county water
safety employees
that surf measurement was actually
the back of the wave!
We get surf observations from
lifeguards and observers that seem to me to be on the
conservative side.
(Peter Cole never has adjusted his
scale downward though.)
You've heard of the difference in
measuring north shore waves in Hawaii even compared to south
shore waves.
So we as forecasters are caught in
this cycle of incorrect measurements, yet we're issuing
forecasts and even high surf advisories based on these
"measurements".
I do still want to thank all water
safety personnel who do a great and courageous job.
Inches of rain or snow are easier to
measure, right?
MY PLEA
Let's quit worrying about what
others think and call it like it is.
I know there is going to be some
differences, but we could all realize the benefits of more
uniform measurements between different locations around the
world. (Sorry so long-winded, yeah!)
Jonathan Hoag
Appendix B
: Greg Small (Associated Press) in Honolulu
Star
Bulletin Online Edition
Sunday, June 24,
2001
http://starbulletin.com/2001/06/24/news/story10.html
Isle converts to
global wave measures
Wave heights taken from the
front go against the traditional method of measure
You'd think that when it comes to
surfers bragging about their prowess, the bigger the waves the
better.
But not here in Hawaii, where one
out of every 10 people surf and, in a sort of reverse-machismo,
surfers traditionally report wave sizes smaller than elsewhere.
While the rest of the world rides
five-footers, those same size waves in Hawaii would be dismissed
as three-footers.
"They'd say 10 feet Hawaii size,
which means 15 feet if you're from New Jersey," said Randy
Rarick, executive director of Hawaii's Triple Crown of Surfing
and regional director of the Association of Surfing
Professionals.
"You're downplaying it to downplay
the seriousness of it," said Rarick, who's also association vice
president.
But wave size is taken seriously by
the National Weather Service, which had to contend with wave
height observations reported by island surfers and lifeguards
that consistently fell short of forecast predictions.
The problem: Scientists and surfers
were using different methods to measure the height of waves.
The weather service forecasts are
based on the international standard of full-face value, measured
from the trough in front of the wave to the top of the wave
crest, said Robert Kelly, weather service director of operations
in Hawaii.
But when Hawaiian surfers look at a
wave across the water, they calculate from median sea level to
the crest.
"Hawaii had a uniquely local system,"
Kelly said.
An estimated 120,000 islanders
engage in surfing and similar activities, such as bodyboarding.
The surfing association in Hawaii has 150 active members at the
pro level and 1,200 members at the amateur level.
The wave reporting system changed in
April, when the weather service finally convinced observers to
report the full-face value of waves, but surfers aren't entirely
giving up their laid-back assessment.
Surf forecasts issued by the weather
service were reworded to take the change into account: "Forecast
surf heights are estimates of the height of the face or front of
waves. This may be up to twice the surf heights traditionally
reported in Hawaii."
Will the change mar the macho image
of Hawaii's sun-drenched surfers?
"Most surfers shrug it off and go,
'Whatever,"' Rarick said. "As a long-time North Shore surfer and
resident, I have to scoff a little bit."
Oahu's North Shore, home of the
famed Banzai Pipeline and Sunset Beach, is where the best
surfers from around the world gather each year for the three
surf meets that comprise the Triple Crown.
Rarick said Triple Crown officials
will go along with the change, but won't completely abandon
local tradition. Competitors will be told, for example, that
waves will be 8 to 12 feet high with a 15- to 18-foot face, he
said.
One surfer, who asked not to be
identified, lamented the change officialdom has imposed on
Hawaii's laid-back surfing community.
"The culture has been assaulted,"
said the surfer, who's been riding Hawaii's waves since the
1960s. "It's been an adjustment for the surfers, and they're
laughing."
Ralph Goto, Oahu's Ocean Safety
Division administrator, stressed that estimating the height of
incoming waves isn't an exact science, because a lot depends on
whether the observer is in a lifeguard tower, on the beach or in
the water.
"No matter how you call it, it's
subjective," Goto said.
© 2001 Honolulu Star-Bulletin http://starbulletin.com
Editor's note : Despite the
well written and researched article, the Honolulu Star
Bulletin loses credibility points by including a surfing
photograph captioned A surfer sailed through one of the big
waves at Sunset Beach in 1998.
The photograph is a large lefthand
tube at Pipeline, surfer unidentified..
Geoff Cater (2005-2015) : Appendix :
Estimating Wave Height
http://www.surfresearch.com.au/awaveheight.html
