While millions of gallons of oil have been spilled in the Gulf of Mexico, the exact total amount of oil that has spilled into the Gulf — and is still gushing — is essentially unknown, despite estimates by BP and federal agencies. The actual volume of oil spilled will affect the chances of oil reaching South Atlantic waters.
Experts also need to know the location of the oil to predict whether it will be caught in currents and/or wind-directed movement of Gulf waters. As of this writing (June 25, 2010), authorities in the Gulf don't have a firm grasp as to all locations where the spilled oil — in various forms — has spread within the Gulf.
Where the oil lies, and at what depths, could play a big part in whether it travels to waters off the South Atlantic states.
Finally, experts need to know the condition of the oil -- how much of the oil has been degraded or dispersed, whether the oil is underwater, in an oil slick, or in tarballs, and so on. All of these factors influence whether or not the oil may reach the South Atlantic.
In late June, NOAA began a three-week survey of the loop current to help answer some of these questions.