The end of august beginning of September is when the northern hemisphere stops getting hotter and starts cooling. It does this equally all over the globe. Just like the random currents in the spout of a draining bathtub natures makes funny shapes when things move at high speed on this planet, constrained by the lower limit of the earth and the upper limit if where clouds can no longer exists, two giant air masses, one hot, one cold meet, and things start moving quickly. When current form a vortex is creates a giant positively charged (because of static/friction) low pressure "eye" that sucks the heat out of the ground and ejects it into space. The ocean in this low pressure zone is raised a bit, and that water is replaced by nearby water.
These are what "tidal surges" are, when large bodies of water experience unusually high and low tides. It's low in nearby areas, especially islands in its wake as the storm carried some of their water away in a giant vacuum vortex that made a big hump in the sea below it as it dragged all that water with it to Florida.
Here's the last photo taken by a Florida Keys web-cam before it went off air.
So that's where it went. It's already on the way back as the storm fizzled out and the pressure is returning to normal.