We know more about hurricanes than ever before. Thanks to advancements in technology and an increased understanding of storm behavior in recent years, meteorologists can now forecast a hurricane’s path and strength with remarkable accuracy. This means they can provide valuable information to emergency managers and other officials, who use the information to make crucial decisions about how to respond to impending storms.
Despite such advances, the way we categorize hurricanes has largely remained the same since the 1970s. And that’s a problem.
The Saffir-Simpson Hurricane Wind Scale is what’s used to categorize hurricanes. As the full name suggests, the scale classifies cyclones according to their sustained wind speeds, from Category 1 (74 to 95 miles per hour) to Category 5 (157 miles per hour and up). The point of the scale is to roughly calculate how much damage to surrounding buildings and the environment can be expected. The higher the category number, the more damage.
The problem is that the Saffir-Simpson scale tells experts only what to expect in terms of wind speeds, whereas hurricanes are multihazard phenomena. Yes, high wind speeds can be deadly and costly, and we absolutely want people in harm’s way to be aware and take appropriate actions to protect themselves. However, other hazards ― like storm surge and rainfall ― are equally if not more important to communicate and understand. Currently, our hurricane scale doesn’t account for either.
Few members of the general public seem to understand that the scale accounts for just wind speed, and many people use the category number to judge how seriously they should take a storm (despite the fact that’s not what the scale was intended to communicate). Research conducted after 2008’s Hurricane Ike in Texas suggested that some people are more likely to evacuate as a storm’s category number rises. This should be of concern to emergency managers, since it implies that fewer people will evacuate for Category 1 and 2 storms, although they are often dangerous enough to warrant widespread evacuation.
The Saffir-Simpson category system tells only a small part of a hurricane’s story, and we need to find a way to tell the rest.
A number of other factors determine whether people will or can evacuate during a hurricane — such as receipt of warnings, access to transportation and health concerns affecting ability to travel — but an understanding of the risk they face is important. Hurricane Florence, the effects of which are being felt across the Carolinas, is a textbook example of why the category approach is problematic. Before Florence made landfall, its wind speeds fell from Category 4 to Category 1, which prompted the media to run headlines that the storm was weakening.
They were technically correct in that its category was lowered, but the dropping wind speeds did not make Florence less dangerous. In fact, in some ways, it became more dangerous. Emergency managers and meteorologists went into overdrive trying to explain why the lower category did not mean that the storm was anything less to fear.
The primary concerns with Florence were never its wind speeds. They were its storm surge and expected rainfall. The lower wind speeds didn’t change affected areas’ high risk of flooding. As of publication, officials reported that 32 people died as a result of the storm.
Hurricane Florence is just the latest storm to prompt this type of confusion. Last year Hurricane Harvey put Texans in a similar position. Although Harvey made landfall in Texas as a Category 4, in short order it weakened to a tropical storm. The size of the storm and its sluggish movement across the state brought a record-breaking 60 inches of rain, the majority of which fell while Harvey was categorized as a tropical storm, not a hurricane.
Relying on the Saffir-Simpson scale can easily mislead the general public as to the severity of a hurricane when high winds are not its most hazardous aspect. Not only does the scale fail to consider hazards like storm surge and rainfall, but it also doesn’t account for how all those hazards will interact with us and our surroundings.
For those trying to manage such situations, the interaction among the hazards and an area’s residents needs to be considered. How will each hazard affect what lies in a storm’s path? Which areas are expected to flood? How badly will they flood and for how long? Who and what are in those areas? Who needs to leave? How do we get them out? Can anything be done beforehand, like putting sandbags out to minimize flooding?
Responding to a hurricane that comes and goes within 24 hours may require a different approach from hurricanes like Florence and Harvey, which stay relatively stationary for several days, dumping record-breaking amounts of rain that lead to widespread flooding. For example, in the former scenario, three days’ worth of food and water is probably sufficient; in the latter, a week’s worth of supplies or more may be needed. Such differences matter when preparing for and responding to a storm.
The Saffir-Simpson category system tells only a small part of a hurricane’s story, and we need to find a way to tell the rest. Instead of focusing on just a storm’s wind speeds, we need a way to account for all aspects of a storm so we can more accurately disseminate lifesaving information to the public.
To achieve these goals, we need a new method or system to accurately communicate hurricane risk. There’s no reason to hold on to a categorization system that experts know is misleading when there are lives at stake.
Samantha Montano has a doctoral degree in emergency management from North Dakota State University. She writes at www.disaster-ology.com.