Freak waves

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teacher · #1 Post by **teacher** » Tue Jan 16, 2007 8:55 am

Interesting article in today's Irish Times about the occurrence of freak waves, which appear not to be 'freak' at all ...

'Freak' waves a misnomer as 15% reach twice average height
Dick Ahlstrom, Science Editor

So-called "freak" waves, such as the one believed responsible for the sinking of the Honeydew II , are in fact commonplace. Studies have shown that 15 per cent of waves will be twice the average wave height at any given time, according to an expert from NUI Galway ...

#2 Post by **Adam S** » Tue Jan 16, 2007 10:52 am

i wouldnt consider a wave of just twice the average size to be "freak" in the sense we tend to refer to them as, certainly the kind of freak waves that sink ships dont occur 15% of the time, of there wouldnt be many ships left

#3 Post by **kieran** » Tue Jan 16, 2007 10:59 am

Hi

There are other reasons why people get swept off rocks fishing around Ireland and one is the nature of the inlet or bay they are using... certainly in parts of Mayo there are deep finger like inlets that slowly shallow as you near the "beach". They often become narrower also and the effect of both these changes is to force the incoming water higher the closer you get to the beach. Some "steps" in the sea bed can produce enormous changes within a matter of a few metres. The result is marks that are, paradoxically, far more dangerous from "freak waves" close in than they are far out nearer the open ocean. Topography is a critical factor and that is why you should invest in an Admiralty chart as well as an OS map...

#4 Post by **round_ourway** » Tue Jan 16, 2007 12:15 pm

Kieran great article in the irish angler it made some good reading

#5 Post by MC » Tue Jan 16, 2007 2:22 pm

was fishing once on a calm windless day on some rocks about 10ft up from the sea and after about an hour I was packing up to move to another mark when a large wave washed over the rocks and reached about chest height. I was lucky it was a calm day as if it was any rougher I was being washed out to sea. To me it was an freak wave, as it has never happened since, even on the same mark.

#6 Post by jd » Tue Jan 16, 2007 2:29 pm

Reading the article, a freak wave is defined as 3 times the mean height. 1 in 7 waves are twice the mean height.
1 in 5000 will be 3 or 4 times the mean.

jd

#7 Post by jd » Tue Jan 16, 2007 2:31 pm

MC wrote:was fishing once on a calm windless day on some rocks about 10ft up from the sea and after about an hour I was packing up to move to another mark when a large wave washed over the rocks and reached about chest height. I was lucky it was a calm day as if it was any rougher I was being washed out to sea. To me it was an freak wave, as it has never happened since, even on the same mark.

If it was calm, it could possibly have been caused by a rock slide or similar in the sea.

#8 Post by MC » Tue Jan 16, 2007 2:37 pm

jd wrote:
MC wrote:was fishing once on a calm windless day on some rocks about 10ft up from the sea and after about an hour I was packing up to move to another mark when a large wave washed over the rocks and reached about chest height. I was lucky it was a calm day as if it was any rougher I was being washed out to sea. To me it was an freak wave, as it has never happened since, even on the same mark.

If it was calm, it could possibly have been caused by a rock slide or similar in the sea.

heard nothing, there was only a large trawler offshore, could that have been the cause

Rockhopper · #9 Post by **Rockhopper** » Tue Jan 16, 2007 3:00 pm

There was a program on BBC a good while back about the sinking of a couple super tankers....the marine scientists had (for years) done tests on wave size related to the Buford scale and said that waves described by old mariners where exagerated....anyways....at certain places around certain coast such FREAK waves do exist...one such place is the Horn of Africa, where they had film of them happening.

The waves shown on the program were big enough to upturn a super tanker either bow or stern first....so much for riding the waves.

What was proved was that many more factors had to be taken into account, like the sea bed, direction of tide to wind...now its not looked upon as an exact science like it was 20 years ago.

All it take is one bump to dislodge the hatch cover of a trawler (like the two that have just been lost) and then a big enough wave to fill her up, that's it...swamped in seconds and down before they can launch life rafts.

I know as anglers we give trawler men some stick from time to time...mostly the ones who trawl beaches...those 2 boats were well offshore...I take my hat off to those guys...they do earn their living the hard way...God rest their souls.

Tom.

#10 Post by jd » Tue Jan 16, 2007 3:27 pm

This is a pretty famous photo of a rogue wave

(Philippe Lijour Esso, Languedoc, off of Durban, 1980)

Another rogue bay of biscayne

#11 Post by **lumpy** » Tue Jan 16, 2007 4:36 pm

with regards freak waves off south africa and other parts of the southern oceans is the fact thet there is little land at this longitude to inhibit wave and tidal movement to an extent that waves have thousands of miles to mature and grow in size and result in extremely large waves.

#12 Post by **jack01986** » Tue Jan 16, 2007 5:17 pm

A large boats wash can cause freak waves. Out in dublin bay one day messing about in a rib the stena ferry had come in and its wash created some very big waves nearly 3m on a flat calm day. We hit the wave and the boat just dropped was not very nice. :shock: Also the waves hitting the cliffs at howth were huge after as well.

Jack.

#13 Post by **corbyeire** » Tue Jan 16, 2007 5:46 pm

they apparantly can only go full speed at a certain distance out from port as the waves are so large they would errode the dunes in the area!

Mr_Green · #14 Post by **Mr_Green** » Tue Jan 16, 2007 6:51 pm

i was down at tramore peir fishing one day and the water was pure flat.... bout 5mins after a big wave came crashing over the peir wall...i looked round the corner and it was calm again and every few mins this happened again and again...i packed up and left...

#15 Post by **jack01986** » Tue Jan 16, 2007 7:15 pm

corbyeire wrote:they apparantly can only go full speed at a certain distance out from port as the waves are so large they would errode the dunes in the area!

Id say so just looking at the swell the HSS and the stena ferrys make coming into the harbour. Some of them are huge.

#16 Post by **Drew** » Tue Jan 16, 2007 7:51 pm

lol.... Ballyhome, and Marks around Bangor get Severe effects from the Stena boats, I've seen me standing on beaches and getting water up to my knees within seconds.
Worst one had to be a local Rock mark... I was standing there quite happily, Not noticing the Super Seacat passing about 20 mins Earlier, when the water was sucked a good 2 Foot down, Followed briskly by the Arrival of some Big breakers... Which I, My Tackle, and my Sandwiches were soaked by. lol...

Never turn your back to the Sea, She be a Harsh Mistress.