If Irma goes up the east coast the concave is right there on Florida, Georgia and S. Carolina meet zone....storm surges will be intense if that happens.
If Irma shifts a few degrees more northerly in its track then it would approach Florida Peninsula where the coast curves back towards the West which gives it more space to make it's northward turn without hitting land. This would be above Palm Beach County.
One indication would be if by tomorrow morning Irma's eye passes directly over or (even better) north of Crooked Island in the Bahamas.