Posted on 06/17/2005 8:41:18 AM PDT by blam
. . . and churn up big waves, too
Sid Perkins
From New Orleans, at the Joint Assembly of the American Geophysical Union
As Hurricane Ivan approached the U.S. Gulf Coast last September, it passed right over an array of seafloor sensors. The network detected the largest wave ever measured by instrumentsone that towered more than 27 meters from trough to crest.
The 50-kilometer-wide group of 14 instruments was deployed in May 2004 to measure currents on the ocean floor, says William J. Teague, an oceanographer at the Naval Research Laboratory at Bay St. Louis, Miss. Late on the evening of Sept. 15, Ivanmoving northward at a pace of about 18 kilometers per hour and packing winds of around 200 km/hrswept across the array over a period of several hours.
The seafloor instruments were set up to take pressure data during 8.5-minute intervals every 8 hours. As it happened, no sensors were making measurements when the eye of the hurricane was directly overhead. However, sensors did record the passing of massive waves before and after the hurricane moved through the array. During one of the data-gathering intervals, waves that often reached heights of 20 m were passing over one sensor every 10 seconds, says Teague. The largest wave in that train measured 27.7 m from peak to trough.
Computer models suggest that the storm's strongest windsthose in the wall of the hurricane's eyecould have spawned waves up to 40 m high.
We have a winner!!
I even managed correct significant digits.
Sorry, I'm an engineer and naturally humor impaired.
Not exactly. Those measurments are peak-to-trough and the trough is often lower than the mean sea level. If you were standing on a fixed platform at mean sea level and one of these 90' monsters passed over it would be less than 90" over your soon to be removed head.
But Thackney only had one decimal point of accuracy. What about those of us (and handy old one was the first) that went the extra millimeter for the second decimal point?
Geeze...
:)
The original number had 3 significant digits. Your conversion cannot gain more accuracy the the original measurement.
Have we destroyed the topic enough yet, or can we discuss the history of the ruler too. ;-)
Ships have been hit by waves almost this big and survived.
http://www.science-frontiers.com/sf109/sf109p11.htm
September 11, 1995. North Atlantic. Aboard the Queen Elizabeth II enroute from Cherbourg to New York.
During this crossing of the Atlantic, the Queen Elizabeth II had to change course to avoid Hurricane Luis. Despite this precaution, the vessel encountered seas of 18 meters with occasional higher crests. At 0400 the Grand Lounge windows, 22 meters above the water, stove in. But this was only a precursor.
"At 0410 the rogue wave was sighted right ahead, looming out of the darkness from 220°, it looked as though the ship was heading straight for the white cliffs of Dover. The wave seemed to take ages to arrive but it was probably less than a minute before it broke with tremendous force over the bow. An incredible shudder went through the ship, followed a few minutes later by two smaller shudders. There seemed to be two waves in succession as the ship fell into the 'hole' behind the first one. The second wave of 28-29 m (period 13 seconds), whilst breaking, crashed over the foredeck, carrying away the forward whistle mast.
..... "Captain Warwick admits that sometimes it can be difficult to gauge the height of a wave, but in this case the crest was more or less level with the line of sight for those on the bridge, about 29 m above the surface; additionally, the officers on the bridge confirmed that it was definitely not a swell wave. The presence of extreme waves was also recorded by Canadian weather buoys moored in the area, and the maximum measured height from buoy 44141 was 30 m (98 feet.)"
http://www.billabongxxl05.com/biggest_wave/
Go here for pictures of the largest waves surfed in the past few years. Most of these were Jet Ski Assisted not paddle in waves.
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The official survey of my land is still recorded in the old Spanish Vara.
27.7 meters = 32 3/4 Varas.
Actually, I'm appalled at the number of folks who couldn't even make the conversion to feet! Thank you, NEA!!
OK, how many Arshins is that?
The condo where we usually go on vacation, located just outside the gates of Johnson Beach Park, which is part of the Gulf Islands National Seashore, is now condemned because of wave action that undermined the foundation of the building. The Southeast corner of the building was the closest to the shoreline of any other that I know of on the Key, and the wave action scoured the foundation causing the building to sag and the balconies there on the south side to start separating from the rest of the building. Looking at the east side of the building, you can see where the windows have warped and sagged, and are coming out of their openings. The wave was also tall enough to go up into the second floor of the condos, and the building was at least 10' above the level of the water, so that sucker had to be at least 25' tall!
I sure hope they rebuild, but as far as I know, they haven't even taken the old building down yet.
My method in reply #7 is easier.
I have two meters on the back of my house, one electric and one gas. They are about 8 inches across. so doing the math tells me the 27 meter wave was about 18 feet.
This happened at sea, so 27.7 meters equals 0.014956803 nautical mile.
One of the earliest types of measurement concerned that of length. These measurements were usually based on parts of the body. A well documented example (the first) is the Egyptian cubit which was derived from the length of the arm from the elbow to the outstretched finger tips. By 2500 BC this had been standardised in a royal master cubit made of black marble (about 52 cm). This cubit was divided into 28 digits (roughly a finger width) which could be further divided into fractional parts, the smallest of these being only just over a millimetre. In England units of measurement were not properly standardised until the 13th century, though variations (and abuses) continued until long after that. For example, there were three different gallons (ale, wine and corn) up until 1824 when the gallon was standardised.
In the U S A the system of weights and measured first adopted was that of the English, though a few differences came in when decisions were made at the time of standardisation in 1836. For instance, the wine-gallon of 231 cubic inches was used instead of the English one (as defined in 1824) of about 277 cubic inches. The U S A also took as their standard of dry measure the old Winchester bushel of 2150.42 cubic inches, which gave a dry gallon of nearly 269 cubic inches.
Even as late as the middle of the 20th century there were some differences in UK and US measures which were nominally the same. The UK inch measured 2.53998 cm while the US inch was 2.540005 cm. Both were standardised at 2.54 cm in July 1959, though the U S continued to use 'their' value for several years in land surveying work - this too is slowly being metricated.
In France the metric system officially started in June 1799 with the declared intent of being 'For all people, for all time'. The unit of length was the metre which was defined as being one ten-millionth part of a quarter of the earth's circumference. The production of this standard required a very careful survey to be done which took several years. However, as more accurate instruments became available so the 'exactness' of the standard was called into question. Later efforts were directed at finding some absolute standard based on an observable physical phenomenon. Over two centuries this developed into the S I. So maybe their original slogan was more correct than anyone could have foreseen then.
- Frank Tapson
...or 0.000000000185 AU
Four and a half rods, thanks, I'm finally beginning to get it. ;9)
1,063,125 Thousands of an inch. That's tall I don't care who you are.
It was severely damaged and didn't record subsequent waves.
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