And you thought it was all to do with seaweed

21st February 2013

Any mariner who has sailed in British waters is almost certain to have encountered the UK Met Office's shipping forecasts: “And now the Shipping Forecast issued by the Met Office, on behalf of the Maritime and Coastguard Agency  …  there are warnings of gales in South Utsire, Fisher,”  and so-on and so-forth.

But the services provided by this famous agency to the maritime sector run far deeper than that, are available worldwide and are extensively used by the offshore oil and gas industry, typically for routeing purposes, during critical in-field operations and for ‘routine’ activities such as survey. The Met Office’s services are extensively utilized by the wider maritime hydrographic survey too … on the high seas and during mundane local port-related activities.

In many respects, the advent of North Sea oil and gas opened a new door for the Met Office back in the 1960s, since when the agency has developed a suite of bespoke services for the industry, gradually taking it international over the decades as demand for such services grew.

It is important to realise that Met Office services, even at their most traditional …  measuring and forecasting weather conditions and systems … are of huge importance to the commercial maritime sector.

“There will be days when conditions are ideal in terms of wind and sea state to do a job but you find you can't do it because of thick fog,” says Aberdeen-based Peter Buchanan - operational services development manager.

“It’s a sad fact of life that when you have very little wind in the North Sea and very little sea, these tend to be the times of fog risk. Sometimes operators forget to take that into account. They’ll look at a forecast and say, oh, not much wind, not much sea, we can do the job. And then find they can't because the visibility is impeding things.

“Perhaps where there is the need for a proper line-of-sight reference point or there may be safety issues that dictate that they can’t operate in poor visibility, or that visibility is physically stopping technical staff coming out to do the job because helicopters cannot fly.”

But its not just about atmosphere, the Met Office is deeply immersed in the oceans too.

“We have to develop a separate modeling environment for metocean because the oceans behave in a different way to the atmosphere. They’re both complex fluid dynamics problems, but they operate differently.

“We have to understand the oceans in terms of wave motion, also in terms of currents. That science has to be applied in a slightly separate modeling environment. But, clearly the atmosphere provides winds and winds drive the waves  so, at some point atmospheric and wave models have to interact, so we have to couple them.

“Similarly ocean models will eventually feed back into the atmosphere because the ocean models will determine ocean currents, currents affect sea temperature, sea temperature affects how the atmosphere behaves, so you immediately have a very complex environment.”

Buchanan says a lot of the Met Office’s R&D effort has been directed at ocean, wave and atmospheric modeling; to make the models more consistently accurate and enable them to forecast more aspects and extend high levels of accuracy into the future.

But he stresses that it is important to recognise that weather forecasts are not perfect. However the times when forecast and real conditions don't match up are decreasing. This has in turn spurred research into that uncertainty in a bid to measure it in an objective way.

“In the past we've done weather forecasts and the client has said we've got to make an important decision. We've got to hire three vessels at £300 000 a day, can we rely on this forecast.

“Before, that was very much a subjective decision and the problem with a subjective decision is that one forecaster might be optimistic while another might be pessimistic so you could technically get a different answer to the same question on the same day.

“We've now tackled that and developed what we call ensemble forecasting … where we do lots of forecasts instead of one. This then brings risk factoring into play. It recognises that forecasts are not perfect, and for a variety of reasons, the most basic being that every forecast model requires initial conditions to base its forecast on. And,  while we make every effort to ensure those initial conditions accurately reflect the then current state of the atmosphere, there is a ‘ball of uncertainty’ surrounding each observation of the atmosphere.”

But its not just today's weather and metocean conditions, or those anticipated several days ahead that are used to inform models and clients, there is also the vast Met Office archive … a process known as ‘hind-casting’. It too can be and is used for planning purposes.

Buchanan: “If you’re planning an operation in the North Sea at a certain time of year that requires operating limits of x sea height or y wind speed and direction, we can look at the archive and that should inform how often such and such an event occurs and what the likelihood of getting it is.

“That can impact when someone plans to do a job and that in turn influences the estimated costs of the job too. The archive therefore can be used even for costing services when the client is getting a tender together and also for building in the risk factor.”

Ocean route planning is clearly critical, but if one is involved in say a significant seismic survey, maybe a 60-day mission around the Falklands, what then can the Met Office bring to the survey company's table?

“We can start helping at the planning stage … find out what time of year, what the critical operating limits are for the job and then supply the client with data.” says Buchanan.

“Before they even start the job they can see how often they're likely to work, what the typical weather is at that time of year and plan accordingly around that.

“In the operating phase, we can provide a variety of products. So, for example, provide a week ahead, site-specific forecast. If we know the route, we can provide forecasts at points along that route and for each point provide quite a high resolution forecast, say every three hours out to a week ahead for factors like surface wind speed and direction, wind gusts; also sea height, main swell direction and period.

“Wave period will affect how the vessel moves. If vessel movement is critical to a particular survey there are other sophisticated tools that we can provide, such as an actual vessel response forecast where we deliver what we call spectral data from the wave model.

“You can feed the wave model spectral data into a response algorithm for that particular vessel. So, in theory, you will be able to work out the pitch, roll and heave of that survey vessel as well from the forecast wave model data.

“In the North Sea, another service we have supplied to survey vessels is surge and tidal information. It may also be for a certain survey that they need to factor in surface current anomalies and, because we run ocean models as well as wave and atmospheric models, we can supply surface current forecasts as well.”

Of course, weather satellites play a very important role in building global and local weather and metocean profiles. They are becoming increasingly sophisticated and can measure a whole range of parameters from space, including sea temperature, wave height and wind speed and direction at the surface of the sea.

“By looking at the interference pattern on the sea's surface, you can also diagnose the wind speed and direction at the sea's surface from a satellite. Satellites are also working at lots of different frequencies so they can tune into things like fog, rainfall and factors like that,” says Buchanan.

There are even spin-offs from technologies that were never designed for weather forecasting, such as satellite navigation.

“We can use GPS data; because the atmosphere bends the signals from the GPS satellites, we can measure that bending and translate it into the amount of moisture in a column of atmosphere. That feeds back into improving weather forecasts.”

And there are other services besides, but the bottom line is that, no matter how well planned you are, or how many precautions you take or how much technology you use offshore, ultimately the weather can be a complete show stopper, shooting from the bottom of the list of priorities to the top in an instant.

“Weather … if its fine, people soon forget about it,” notes Buchanan, warning: “The weather starts going bad, the job gets off schedule, the client puts pressure on the contractors and then the weather suddenly shoots from no-one's really bothered about it to massive pressure on the forecaster or provider to let them know when its going to get better again.”



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