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Conference unifix::sailing

Title:SAILING
Notice:Please read Note 2.* before participating in this conference
Moderator:UNIFIX::BERENS
Created:Wed Jul 01 1992
Last Modified:Mon Jun 02 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:2299
Total number of notes:20724

2191.0. "wave heights and NOAA forecasts" by UNIFIX::BERENS (Alan Berens) Mon Jan 23 1995 21:16

At least in Boston, the NOAA marine weather forecasts now give the 
expected wave heights as the average of the highest one-third of all 
waves. So?

Well, this means that, if H is the average of the highest one-third of 
all waves,

   0.50*H will be the most probable wave height

   0.63*H will be the average height of all waves

   1.27*H will be the average height of the highest one-tenth of all 
   waves

Moreover, there is about a 5% chance that the highest of 200 waves will 
exceed 2*H. In a 24 hour period, there is about a 5% chance of 
encountering a wave 2.5*H. Hmmmmmm.

For much more information, see chapter 16 in "Oceanography and 
Seamanship", 2nd edition, William G. Van Dorn, Cornell Maritime Press, 
1993. 
T.RTitleUserPersonal
Name
DateLines
2191.1rollercoasters or berms?MILKWY::WAGNERThu Jan 26 1995 11:3110
    	Tellya what, as long as that 25' rogue is greater than 500' between
    crests, bring it on!
    
    	As an aside, with all the death/destruction in Kobe and environs,
    has there been any wave action mentioned? 
    
    	I think the next great instrument is a satellite waveshape
    indicator, to go with the laser windshift reader!
    
    	TechnoRoboScott
2191.2No action from KobeORCAS::JESCHKE_ANThu Jan 26 1995 15:1813
    re -.1
    
    I heard  there was no reason to issue a Tsunami waring after Kobe.  A
    few months ago,  when northern Japan had a 6.something, warnings were
    issued for Hawaii and the west coast.  That one fizzled before it got
    close to Kona land.
    
    Those suckers must really move - I think they predicted only 10 to 12
    hours to make the trip across the pond.
    
    
    Andy
2191.3'Tsunami haul ***TINCUP::CLAFLINFri Jan 27 1995 12:5818
I forgot the exact number, but Tsunami's travel at something like 450 mph in the 
open ocean.  They are quite small in deep water, about three feet high, and
may easily pass without being noticed.

I sow some pretty impressive pictures of Tsunamis hitting land in a book at the
Worchester Public Library.  They looked like primarily pictures from the 50's
in Japan.  One picture stands out vividly in my memory.  There are alot of 
people literally running for their lives.  The Tsunami is breaking over the 
one and two story buildings down the street.  It is a breaking wall across the 
entire picture.  The photographer is perhaps a hundred yards away at the time
he took the photo!  Even more amazing is that at least the camera survived.

I do not know who they decide when to issue a warning, or for how far away.
Obviously an under sea quake is more likely to form a tsunami than one on land,
but after that, I have no idea.

Doug Claflin
dtn 592-4787