Its not as simple as a Cat 1 can cause this much surge. This was not an ordinary Category 1 storm. it was extremely large, and on top of that was interacting with a very strong high pressure system. Those two elements created a strong pressure gradient that delivered a 200 mile swatch of NW 50-60 MPH winds that drove insane amounts of water into the FL coast. A similar Cat 1 storm (Katrina) was in a similar situation and evolved much differently as a storm with respect to storm surge. There have been several hurricanes that have greatly overperformed their storm surge values due to extreme large fetch of winds (Ike, Nicole, Sandy, etc).