That left the storm heading straight for Florida’s western coast.

Irma’s path still depended on the strength of the trough. The dry air had the potential to strengthen Irma's path and aim its storm surge toward the Everglades. But it also might be too weak, in which case Irma would shrug it off and continue northwest, along the coast.

Over 4 million people live along Florida’s west coast, stretching from Everglades City to the edge of the Florida Panhandle. For each coastal city, the worst-case scenario was for Irma to come up alongside it, pushing a massive storm surge into densely populated beachfront neighborhoods.