Many readers will have seen the scary movie showing the Gulf oil spreading into the Atlantic.
I ask you to compare the movie against this widget at the New York Times which shows actual historical behavior of the spill.
What you will see is that the loop current is continually pulling a filament of thin oil out to sea (comparable with the UCAR simulation movie) but that the filament is continually dissipating. In the simulation, that phenomenon is not visible at all.
My understanding of what is going on is that they initialized the standard NCAR ocean model http://www.ccsm.ucar.edu/models/ccsm3.0/pop/ with observations, continually injected passive tracer at the surface, and drove it with climatological winds.
I'm only slightly less sure that the biggest problem with the simulation is that they neglected the oxidization of the hydrocarbons by various processes.
If you actually watch the oil slick pattern, it's clear that the parts that grabbed by the loop current get thinned out enough to pretty much vanish a day or two later.
I think it would have been better (and just as easy, though anything with these models is not easy, running these codes is like going back in time thirty years as far as software ease of use goes) to have a simple half-life on the tracer. That would also be wrong, I would guess, but not as wrong. I don't think treating the oil as a passive tracer yields a good picture.
My wife would not like it if I made a substantial bet, but I'd happily bet that there will be no impact of any consequence anywhere in the Atlantic, say, north of Key Largo.
This is not to say that I am happy with the situation in the Gulf. But I'm starting to see the problem that many people have with others' eagerness toward predictions of catastrophe. So far there is no sign in the real world of anything like the model's scenario happening.