Forthright Irma: A discussion of Hurricane Ambiguity.

It’s hard to get people to evacuate. Cara Cuite and Rebecca Morss–risk communication and hurricane experts–write about several factors that can cause people to ignore evacuation warnings. Things like: some people don’t like being told what to do; sometimes they judge fear-based messaging as “overblown” and disregard it; sometimes the cost and logistical nightmare of evacuating causes them to prefer to shelter-in-place. (Do read their article; it’s so interesting.)

But my favorite factor which causes people to ignore evacuation warnings is ambiguity. Ambiguity is systemic and unavoidable and–worse–humans are terrible at managing it. Some individuals and cultures are better at tolerating uncertainty than others (as Hofstede points out), but generally humans don’t like to take action when they can’t predict the outcome.

This trait can influence Emergency Managers’ work in two ways: 1. Storm prediction is inherently ambiguous which makes our jobs harder and 2. Ambiguity from authorities causes people to hesitate putting them in danger.

1. Storm prediction is ambiguous

Below is a comparison of American (blue) and European (red) computer models predicting the path of Hurricane Irma. The darkest lines are the averages. (Thanks to the Washington Post for this picture and many other excellent ones.) As you can see, there is a limit to how finely science can predict a hurricane’s progress. Imagine you’re the governor of Florida. Do you evacuate Jacksonville?

Irma prediction model
Group of simulations from American (blue) and European (red) computer models from Friday night [9/8/17]. Each color strand represents a different model simulation with slight tweaks to initial conditions. Note that the strands are clustered together where the forecast track is most confident but they diverge where the course of the storm is less certain. The bold red line is the average of all of the European model simulations, while the blue is the average of all the American model simulations.(StormVistaWxModels.com)
Fortunately for the real Governor of Florida, storm prediction has vastly improved since the deadliest storm in American history–“The Galveston Hurricane of 1900″ (This was before they started naming storms). During the 1900s, American meteorologists had a poor understanding of how storms played in the ocean. Though the more experienced Cuban meteorologists warned of an incoming hurricane, the message was ignored and no one evacuated. Surging waters killed 8,000 of the 37,789 residents or about 20% of the population.

After World War II, “the U.S. still used pretty simple forecasting tools. Airplanes took rough rides into these tempests, found the storm’s center, and then returned every six hours to find the center once again,” reports Popular Science. The U.S. launched it’s first weather satellite in 1960 and the first satellite images were broadcast on television in the 1970s.

The last decade or so has seen even greater improvements of predictions through better satellite technology and computer modeling. The Natural Hazards Review estimates that weather satellites have prevented up to 90% of the deaths that would have occurred had meteorologists not had satellites available. NOAA reports that their errors in storm tracking has dropped by 50% in the last 15 years while in the last 5 years, NOAA has improved it’s notice-giving by 12 hours. Public officials now have 36 hours of advance notice. If it hadn’t been for these improvements, weather experts estimate 10,000-20,000 people killed in Hurricane Katrina, instead of the actual 1,200 people. Because of storm tracking, only 15% of New Orleans’ population was still in the city.

The bad news is that there is still ambiguity to storm tracking–for instance, scientists still have a hard time judging the intensity of a storm. The good news is, the ambiguity is way less than it was before.

2. Ambiguity from authorities can cause inaction.

The ambiguity from storm prediction can creep into the language used by public leaders which directly causes people to hesitate to take action or to disregard warnings. Studies show that people use multiple sources of information when trying to make a decision and that people are more likely to take the action when a) sources agree and b) information is consistent over time.

Let’s compare the evacuation orders from Hurricane Harvey and Hurricane Irma. Evacuation messaging for Hurricane Irma was consistent and forceful and Florida evacuated smoothly. On the other hand, Texas officials have been criticized by some for their weak and inconsistent evacuation directions.

Before Hurricane Harvey, Houston Mayor Sylvester Turner told residents to shelter-in-place. Meanwhile, Texas Governor Greg Abbot said, “If you have the ability to evacuate and go someplace else for a little while, that would be good.” This mismatch in message caused many residents to stay put. In Mayor Turner’s defense, he was expecting flooding instead of high winds and driving in flooded streets is far more dangerous than staying in your house. The two public leaders judged the ambiguous weather data differently from their different vantage points.

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Pic courtesy of NPR

Additionally, Gov. Abbot’s “evacuation order” seems weak. The “If you can…that would be good,” sounds like a suggestion on par with “If you could get me butter at the store, that would be good.” At first, I was frustrated because I assumed Gov. Abbot was just a bad public speaker. “Do you want people to evacuate or not?!” I yelled at the TV. (Please forgive me, Mr. Governor.) But after reflection, I think his message was ambiguous because it had to be. Here are the facts I imagine are in Abbott’s mind: 1. I want you to evacuate. 2. Evacuation causes traffic jams. We all remember the horror of the 2007 evacuation from Hurricane Rita–the largest evacuation on record. 3. Smart people are telling me that this could just be rain, in which case I don’t want millions of people flooded and drowning on the highways. 4. If I explicitly call for voluntary evacuation, people might evacuate from safe areas blocking the road for people trying to evacuate from dangerous areas. Poor Gov. Abbot. Not only is there ambiguity arising from the limitations of science and from different vantage points, but there is ambiguity in messaging because of conflicting motivations.

Fortunately, evacuations for Hurricane Irma went smoothly. We could make the argument, as Alan Bernstein, spokesperson for Houston Mayor Turner does, that this was due to Irma’s certainty. He said to NPR, “Irma is totally different. It is forecast for a direct hit on populous areas, bringing highly destructive winds and perhaps heavy coastal destruction. That was not the case here, and Mayor Turner would not second-guess an evacuation order for Florida.”

 

All I can say is: Thank God for better storm tracking.

Further Reading

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