I’'ve crossed the Pacific many times in winter. In the case routing on the 27th/29th I’d be looking for a route not to exceed 7 meters. It’s important to understand that 7 meters seas(SWH) are what a bullshitter calls 35 foot seas.
and so whatever is your point? this week will be a toilet boil out there in the Gulf…nough said unless you have some point to prove to the unwashed such as myself?
Mariners should understand what the numbers on the chart mean in real terms to avoid being surprised by larger waves than expected.
I can’t think of any way to dumb it down more than that.
This is from the NWS article:
Mariners can reduce their risk of encountering bigger than expected waves by understanding the range of wave heights in a spectrum defined by a particular significant wave height
I’ve tried explaining that to a few people to get blank stares. There look at the forecast calling for 4-6 ft (occasional 10ft) and say, “We’re gonna be in 10 footers!”
There is a lot of chaos, uncertainty, imprecision and error in the world, not least in marine weather. When a wave height forecast is given using significant wave height (SWH) of course there are many possible sources of error, but there is no reason to introduce unnecessary errors if it can be avoided. Not understanding or misusing SWH is is an easily avoided error.
Point being, don’t make things harder than they already are.
I have experienced +70 ft. waves (Wmax) that was actually documented.
In Nov. 1981 I was Marine Advisor on LB 200 in the Statfjord Field in the northern North Sea.
We were moored close to Statfjord B platform with 12 anchored and a total of 550 pers. on board when we got hit by a freak storm from the North east.
We disconnected and moved off to 1200 ft. from the platform as per standard procedure, but continued shuttling personnel to/from the platform for shift change with 3 helicopters. At abt. 70 kts. sustained wind the platform called a stop because they were afraid somebody would be blown of their helideck.
At the peak we recorded 130 kts.gusts on top of the Tower of LB 200, while our standby boat recoded 120 kts. before the anemometer blew out of the mast. The wave rider buoy in the Statfjord field recorded Wmax of 23 m. (75 ft.)
There was a picture taken from Statfjord B as a large wave hit us with spray flying way above the tower,
(It was used by somebody for advertisement for a while but I’ve been unable find it)
I did find this picture by Scanpix though:
The Navtex/SavetyNet High Seas Forecasts for the different Metareas begin with this text (NWS):
Seas given as significant wave height…which is the average height of the highest 1/3 of the waves. Individual waves may be more than twice the significant wave height.
This introduction is also used (Meteo France):
Please be aware, wind gusts can be a further 40 percent stronger than the averages given here, and maximum waves may be up to twice the significant height.
Hence, the significant wave heights shouldn’t be such a surprise for someone near a bridge.
The maximum wave heights at a given position are not foreseeable; the definition is a mathematical probability. At least in theory, the maximum height is not limited: Once in a billion of years, with this exact weather pattern and at this exact position…
With the significant height, the rare rogue waves disappear in the huge mass of normal waves.
Well working on Large ATB’s in the GOM, my Captains always said that it seemed if you added up (6-10 foot) you got closer to what the actual sea heights were. They judged this by the wave height and the Cargo Deck which was 17 feet above the Main Deck.
my condolences ombugge, when we saw that shit coming we were at least able to hide somewhere, And Kennebec, What a mosel reading Chaos came from meteorology… then again, it might figure being tied to global fund raising… er, i mean global warming!!
But above all this is C. Capt. and where we’d all rather be on those super yachts with all the babes… I guess i could of appied for one of those jobs but it sounded pretty risky to me and I didn’t think I could accept the atmosphere of what may pass for “mariners” with those outfits.Pictures of 70+ foot seas
I’ve fought many a Hundred footer outside the Belle Pass jetty.
The reason official wave height reports use significant wave height, the average of the highest 1/3 of the waves, is because that closely matches observations by mariners.
In other words when mariners measure wave heights by eye they ignore the smaller (not significant) waves. For example in say 10 foot seas a mariner observing the waves is going to ignore the one foot waves in the mix that a weather buoy would sense and use in a calculation to determine the average wave height.
The 1979 Fastnet and 1998 Sydney to Hobart are the two offshore yacht races that are most famous for being hit by storms much stronger than had been forecast. There’s quite a bit of literature and first hand accounts of the storms and seas described as 50 feet high or more. One eyewitness account from the Fastnet:
The inquiries that followed caused large changes in the safety and preparedness rules for offshore events, but to this day people die racing (two so far in the current edition of the Clipper race).
The boats in the currently-running Volvo Ocean Race have multiple hi-def video cameras that are being continuously recorded; if anything interesting happens a crew member can press a panic button that saves the last six minutes. Maybe we’ll get good video of huge seas during the next leg that goes through the Southern Ocean from Cape Town to Melbourne departing December 10th - but with today’s forecasting and routing technology conditions that bad could/should/would be avoided.
Just another week or more circling a rig or platform in the North Sea during autumn/winter.
Here is the vessel from where this was filmed. Now GS Protector and still active as EERV in the North Sea:
PS> That would be a nice time to have X-bow and X-stern.