Predicting where the Gulf oil will go

Oil reaches Louisiana coast

* Heating up with humidity, too: Full Forecast | WaPo oil photo gallery *

Past and predicted oil spill location. Courtesy NOAA.

Mother Nature is no longer helping matters in the Gulf of Mexico, where the Deepwater Horizon oil rig exploded and collapsed on April 20.

For a time, winds mainly from the north and west had kept the sheen of expanding oil in the Gulf of Mexico away from the Gulf Coast. But that started to change Wednesday night, when winds shifted and began to blow from a more southerly direction. The onshore flow, which has now brought the outskirts of the oil spill ashore in Louisiana, is expected to persist at least through the weekend, raising the prospects for devastating effects on the environment, wildlife and economy.

Wind direction alone is far from the whole ballgame when it comes to predicting the movement and spread of an oil slick.

Compass direction from which near-surface winds were reported Tuesday night through Friday morning. Courtesy NOAA/NWS/NDBC.

Other factors include surface currents, wave action, tides, air and water temperatures, salinity, and characteristics of the local shoreline and sea bottom. Knowledge of each of these interacting components is required as input for mathematical models used to forecast the evolution of an oil spill. The grade of oil (e.g., light, medium, heavy), depth of the oil slick, and the chemistry of oil degradation given environmental conditions also come into play.

NOAA graphic showing predicted oil spill location for May 1. Black outline indicates radius of uncertainty. (Full graphic)

The most common models for oil spill prediction, such as those used by NOAA, are known as trajectory models. Such models generate the predicted trajectory, or track, of many small "parcels" of oil, which collectively provide the basis for charting the movement of the entire spill. As we all know, any model involving weather has its limitations. The black outline in the image to the right indicates the area of uncertainty for Saturday's predicted oil spill location.

Only time will tell whether response efforts, supported and guided by modeling capabilities, will be enough to avert or mitigate the potential environmental and economic damages threatened by the oil now oozing toward the Gulf Coast. In the meantime, it seems the Gulf Coast is once again at the mercy of Mother Nature, this time a full month before hurricane season even gets underway.

One of the better websites to stay up to date on the oil spill is "Gulf of Mexico - Transocean Drilling Incident" at http://www.deepwaterhorizonresponse.com/.