The Saffir-Simpson Hurricane Wind Scale

The Saffir-Simpson Scale has been used for several decades to categorize the severity of hurricanes in the North Atlantic and eastern North Pacific Oceans (and in other areas of the world, too, although unofficially). While much of the public may not be aware of the name of this scale, they are aware that it exists, and are familiar with hearing the terms Category 1, Category 2, etc. when the media provides information about hurricanes. The scale was developed by a civil engineer and a meteorologist (Saffir and Simpson, respectively) in the 1970s primarily to predict the amount and type of damage that a hurricane would cause upon landfall. The sustained wind speed of the hurricane determined its category, and each category was associated with a range of expected storm surge. Storm surge is the phenomena that causes the most damage with landfalling hurricanes, so the scale can be used by engineers, emergency planners, and other public officials to prepare for the aftermath of a hurricane. In fact, the scale was designed for this use, and was never meant to come into the widespread public use that has evolved through the years. 

In recent years, the scale has come under some scrutiny for its oversimplification of storm surge prediction. In fact, more recent research has indicated that storm surge is a factor of more than just sustained wind speed. Other factors such as the physical size of a hurricane, local bathymetry (geography of the ocean bottom), shape of the coastline, speed of advance of the hurricane at landfall, angle of approach to the coast, and state of the tide at landfall all come into play. In fact, there have been several cases where landfalling hurricanes of a given category have produced storm surges much greater or much smaller than the scale predicted.

With a rather active period of Atlantic hurricane activity in the past 10 to 15 years, and the widespread use of the scale by the media, another phenomena has arisen. This has to do with the perception by the public that the only hurricanes that require any significant preparation are those of Category 3 and higher. I have heard of people under a hurricane warning saying, “Oh it’s only a Category 1, there is nothing to worry about!” In fact, a Category 1 hurricane will produce sustained winds of 64-82 knots with higher gusts, and these winds will cause damage.

For these reasons and others, the National Hurricane Center is redefining the scale for 2009, and calling it the Saffir-Simpson Hurricane Wind Scale. The scale will no longer have storm surge ranges attached to the five categories, and will no longer have ranges of central pressure associated with the categories either. It will be purely a wind scale with the same ranges of wind speeds as in the earlier version. The presentation of the scale will be different in that in place of the storm surge values, a description of the types of damage associated with each wind category will be provided. Examples of recent hurricanes which fall into each category are also provided. Storm surge information, which is still clearly very important, will be provided separately which will allow forecasters to take into account all of the other factors which contribute to this phenomena and generate a more accurate and precise prediction. Here is a link to the new Saffir-Simpson Hurricane Wind Scale:

As we move into the active portion of the hurricane season in the Northern Hemisphere, this is a good time to check your hurricane preparedness. And please, never let your guard down for “only a Category 1” hurricane! 

By Ocean Navigator