So, how does this energy get from the ocean into the sky? It happens when water evaporates from the sea surface. In turn, this heat energy is released into a developing tropical storm as condensation occurs.
The resulting temperature gradient between the warm interior of the storm and slightly less warm surrounding environment creates a large pressure gradient.
This is what drives the powerful winds of a hurricane. As long as this system is undisturbed (and wind shear does not come into play), the hurricane will maintain its intensity or grow even stronger.
So when a storm like Hermine moves over land, the game is over is far as high winds go. However, when the winds do slow down, something very important happens. The pressure gradient force suddenly overwhelms the outward centrifugal force and the storm collapses on itself. The converging air causes more upward motion, and rainfall rates usually increase.
This is what we are seeing now with Hermine, and the remains of the storm will continue to produce very heavy rainfall across the South Central states through Wednesday.
Story by AccuWeather.com Senior Meteorologist John Kocet.