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Thursday, August 24, 2006

Marine accident brief on Norwegian Dawn

It was fervent news reported world wide when the cruise ship Norwegian Dawn was hit by a freaque wave in Atlantic Ocean off South Carolina coast in April a year ago. As far as encountering with freaque waves is concerned, this event must be considered a very fortunate case. Because from all indications they were indeed struck by a freaque wave, but only sustained minor damages. In November 2005, the U.S. National Transportation Safety Board issued an investigation report “Marine Accident Brief” which, surprisingly, did not received as widely news coverage as the event when it was happened.

May be the reason for the lack of newsworthiness is the rather less than sensational conclusion found:

“The National Transportation Safety Board determines that the probable cause of the damage to the Norwegian Dawn and of the injuries suffered by its passengers was wave breaking over the bow during the ship’s unavoidable encounter with severe weather and heavy seas.” (Bold faced emphases added.)

Nothing there for the ambulance chasers or the finger pointing media types. But for the freaque waves studies, I think this is a very useful investigate report for a rare freaque wave event that can be investigated in detail. Here's a picture showing the damaged spots after the freaque wave hit:










I found the following paragraph in the damage report of particular interest to the freaque wave studies:

“At 0610 on April 16, the ship was making 7 knots over the ground. The wind and sea conditions had eased slightly, according to ship’s officers and log entries. However, the watch officer on the bridge observed the vessel pitching and saw the bow start to plow into the seas. The master, who had been on the bridge throughout the night, told investigators that he felt the ship pitch three times in succession. The watch officer stated that all the waves were very large, and that all were roughly the same height. On the third wave, he said, the ship’s bow took heavy green seas, which at 0615 cascaded directly over the bow and struck the forward part of the vessel’s superstructure.”

Two important notes should be striking here: First, the event occurred when “the wind and sea conditions had eased slightly,” so the event did not happen at the peak of the storm; and secondly, the watch officer stated that it was the “third” wave that provided the heavy hit, even though “all the waves were very large, and that all were roughly the same height.” Therefore it seemed that the third wave could still be conceivable larger than the others or the freaque waves are not necessarily single wave events.

This is the kind of occasion that one would really wish a wave recorder could have been installed on the vessel. I, for one, would earnestly prefer to see that all sea-going vessels should be required to equip with continuously operating wave recorders. The added coast will be basically insignificant, but the benefit to the navigation and possible improvement in knowledge in the long run will be simply immeasurable.

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