Measuring hurricanes

There are some real, and potentially deadly, problems with our reliance on the Safir-Simpson scale for gauging the size of hurricanes. Wind speed is just one component in measuring the destructive power of a storm. Other factors, in combination with and even on their own, make such storms deadly.

• Storm surge. As we're seeing with Ike and as we saw with storms such as the New England Hurricane of 1938, can kill more and faster. The slow-moving tsunami pushed by the storm as it makes its way across the ocean can raise the water level from a few inches to many feet in minutes. In Providence in 1938, "the surge hit the downtown business district. In Exchange Place, water which had been just a few inches deep was waist deep within minutes. It rose to a remarkable 13 feet 8-1/2 inches, exceeding the level marked on the Old Market Building after the Hurricane of 1815."
• The dimensions of the storm. Again, from the National Hurricane Center, "Ike remains a very large hurricane and hurricane force winds extend outward up to 120 miles...195 km...from the center...and tropical storm force winds extend outward up to 275 miles...445 km." Most hurricanes, even ones with much stronger winds, are half that size. The range of destruction is spread across a much wider area.
• Rainfall. Fay, a tropical storm when it reached Florida's west coast a few weeks ago, had top winds that barely reached 60 mph. It moved so slowly, however, meandering around central Florida like someone's drunken aunt, and delivered up to two feet of rain.
  

The Safir-Simpson is a convenient way for the news media to tell a part of a story. It brings us an interesting fact that can obscure our awareness of other even more important fact.