Michael wasn’t organized enough to merit a name until Sunday, but it intensified quickly in the warmer-than-usual Gulf of Mexico and became the Atlantic season’s seventh hurricane on Monday.
It continued to strengthen as it neared the coast, energized by increasingly warmer water.
Storm surge is worst on the east side of a north-moving hurricane such as Michael, where the strongest wind acts like a bulldozer shoving water toward land.
This area of Florida is particularly susceptible to storm surge because the water is so shallow. Unlike some areas where the coast drops off quickly, the continental shelf here slopes gradually out for 70 to 90 miles. A big rush of wind-driven water has little to slow it as it rolls onto land.