It is really hard to know what exactly is ironic, but this situation would be if it happens.
Imagine: a Category 5 hurricane is barreling down on New Orleans. The damage is expected to be devastating, to say nothing of the oil slick that the storm surge will bring ashore.
Then, as the storm hits the site of the Deepwater Explorer fire. The oil slick, coating the surface of the Gulf of Mexico, prevents water vapor from rising up and feeding its heat into the storm. Starved for heat, the Hurricane dies out and hits the coast as little more than a tropical storm.