WILMA'S SURGEMany persons who have experienced the eye of a hurricane have witnessed its calm, quite low, wind velocities and also its "very high tides." This tide phenomenon is more precisely termed storm surge. High water levels in the eye of a hurricane are caused by atmospheric air that surrounds the storm at a distance. The pressure of that air acting downward on the surface of the surrounding sea causes flow of water toward and upward into the low pressure region created by the eye of the storm. What water surge height might have occured in Wilma's eye?

♦  To fashion a solution we create a ficticious system as a manometer that extends from far out to sea where the pressure is atmospheric (1013 mbar) all the way the the center of the hurricane, to its eye, where the pressure is 882 mbar.

The sketch depicts a long open-both-ends pipe or tube full of sea water that extends from A, to C. The beginning point A is selected because we know the pressure there (far out to sea) is atmospheric. We use the hydrostatic principle to imagine how pressure changes along points of the path (inside the pipe) from A to B. Water at A has the same elevation as the water at B, hence the pressure at B is 1013 mbar. Point C, above B, has the pressure, 882 mbar. By the hydrostatic principle:

p_B - ρ_{sea water}g_o H_surge = p_C

Although the above equation could be re-written to get the answer, H, alone and left of equality, resist premature algebra. Keep the equation intact. Let it flow down the page until it contains nothing but numbers and H. Then apply algebra.

1013 mbar - (1025kg/m²) (9.81 m/s²) H = 882 mbar.