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GNOME's Trajectory Predictions

NOAA OR&R's oil spill trajectory model, GNOME, uses wind and current information, along with information about the type of product spilled and the strength of the turbulence expected in the water, to predict the trajectory of spilled oil. It displays this forecast as an animation in which the oil is depicted as a swarm of dots, called "splots," each representing a portion of the volume of spilled oil.

Now Showing: the Columbia River Estuary

On June 14, 1999, tides along the northern Oregon/southern Washington coast reached their lowest levels in 17 years, creating unusually strong currents within the Columbia River Estuary. We prepared some QuickTime movies showing GNOME's predicted trajectory for a fictional spill of crude oil in the estuary on that day.

The Spill Scenario

At midnight on June 14, 1999, about 100 barrels of crude oil spills into the Columbia River Estuary off Astoria, Ore. Throughout the day, as the slick moves and spreads on the water, it is affected by:

  • winds, generally out of the south at 4 to 6 knots.
  • currents in the area, stronger than usual because of the large tidal range.
  • the turbulent processes affecting any large body of water.
GNOME's Best Estimate

View GNOME's "best estimate" of the oil's trajectory.

In this animation, the location of the spill is represented by a small "plus" sign. GNOME predicts that most of the oil will move towards the northwest (shown by the movement of black splots), and that by the end of the day, much of it will have beached along the northern (Washington) bank of the river and in Baker Bay.

The "Minimum Regret" Case

Besides making a best estimate of the oil's trajectory, GNOME also can predict the effects of uncertainty in winds and currents. (Uncertainty arises from things like errors in forecasts of winds or current patterns.) These effects are depicted in the trajectory animation at right.

In this animation, the location of the spill is again represented by a small "plus" sign. This time, red splots mark additional places where oil may move, beyond the areas where GNOME's best estimate expects oil to travel. You will note that the minimum regret estimate affects a larger region, including more oil floating on the river and more beached oil.

In a real-life event, roughly 90 percent of the time, the spilled oil is not expected to travel beyond the area covered by the red splots (assuming that the scenario information has been correctly entered into the model and that our understanding of the underlying regional physical processes controlling the spill trajectory is correct).

More Information about GNOME Trajectories

Download GNOME and try your hand at this oil spill trajectory model.

GNOME comes with a Location File for Central Long Island Sound. (Location Files contain prepackaged information about tides and currents for a particular place. They make it easier to predict the possible path of oil spills in a region but should not be used to model a real oil spill.) You can find more Location Files, and other resources to help you build your knowledge of GNOME, on our Location Files page.

Go back to the GNOME FAQs page.

Last updated Tuesday, July 19, 2016 1:05pm PDT