The Cone of Uncertainty And How To Read A Hurricane Map : Short Wave Federal forecasters are predicting a busy hurricane season this year — three to six of them could be major hurricanes. So how do you know if one is headed toward your community, and if so, how to prepare? There are maps and forecasts, but they're often confusing. NPR climate reporter Rebecca Hersher explains how to avoid the most common mistakes.
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How To Know If A Hurricane Is Coming For You

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How To Know If A Hurricane Is Coming For You

How To Know If A Hurricane Is Coming For You

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MADDIE SOFIA, HOST:

You're listening to SHORT WAVE from NPR.

EMILY KWONG, HOST:

Hello, Rebecca Hersher, NPR climate reporter.

REBECCA HERSHER, BYLINE: Hello, Emily Kwong, benevolent warrioress (ph).

KWONG: Oh, why, thank you.

HERSHER: Guess what?

KWONG: What?

HERSHER: It's hurricane season.

KWONG: Oh, man.

(SOUNDBITE OF NEWS MONTAGE)

UNIDENTIFIED METEOROLOGIST: Everybody wants to know, how busy is this hurricane season going to be and how bad? Well...

UNIDENTIFIED METEOROLOGIST: The 2020 Atlantic hurricane season's been the busiest on record. Look at all...

UNIDENTIFIED METEOROLOGIST: This is shaping up to be a busy weather weekend with three major tropical storm systems expected to make landfall.

KWONG: Yeah. I mean, we've already had a few big and deadly storms - Isaias most recently. It's shaping up to be a pretty active season, Becky.

HERSHER: Yeah, for sure. Federal forecasters have been saying for months that conditions are really good for hurricanes - which, you know, bad for humans.

KWONG: Yeah.

HERSHER: They're predicting more than average. That means 19 to 25 named storms - like tropical storms and hurricanes that get big and powerful enough to get their own name - and then three to six of those are forecast to be major hurricanes. So that's hurricanes that are powerful enough to blow the roofs off some homes, cause really serious wind damage.

KWONG: And that's scary in any year, but it's extra terrifying this year with the pandemic, right? 'Cause people are trying to stay home, but these storms could actually make it not safe to stay at home.

HERSHER: Yeah, exactly. And that's one reason that it's extra important this year to understand the public information about where hurricanes are headed and how they're going to affect people...

KWONG: Absolutely, yeah.

HERSHER: ...Whether that's wind damage or flooding, so people can prepare correctly and have as much time to prepare as possible.

KWONG: So how do you prepare? Because aren't there forecasting maps for that?

HERSHER: Yeah. There are maps.

(SOUNDBITE OF MUSIC)

HERSHER: But looking at one, you might not draw the right conclusion. There is some research that suggests that actually a lot of people misunderstand hurricane forecasts. It's not their fault.

KWONG: Wow.

HERSHER: Those maps you're talking about, they're really confusing. And they're not really meant to give regular citizens all the information they need about how to stay safe during a hurricane.

KWONG: So today on the show - when a hurricane is on its way, what do you do?

We're going to dissect hurricane forecasts - what they do and don't tell you.

HERSHER: And how to avoid the most common mistakes people make when they see hurricane forecasts.

(SOUNDBITE OF MUSIC)

KWONG: OK, Becky, we are doing a little Understanding Hurricane Forecasts 101. Let's say a hurricane has just formed in the Atlantic. We'll give it a name.

HERSHER: Maybe Hurricane Duncan?

KWONG: Hurricane Duncan is ripping through. What happens?

HERSHER: So Hurricane Duncan has just formed, and the National Hurricane Center down in Miami is tracking where it's headed. So one of the first things, if this were to happen, that they would do is publish a map. And you've probably seen this map. It's got a little dot or an X where the storm is, out in the water. And then there's a rounded cone extending out from that point toward the land. And basically, it shows where the storm will go.

KWONG: Yeah. To me, they look kind of like tadpoles.

HERSHER: (Laughter)

KWONG: I don't know if it looks that way to you (laughter). You know, you have like a tapered end and then a blob on the other, kind of extending outward. They're usually all over Twitter and TV weather broadcasts when there's a hurricane predicted.

HERSHER: Yes, exactly. You nailed it. It's an incredibly popular map. A lot of people see it when a hurricane is headed for land. And so a lot of people use them to figure out if the storm is headed their way. And the folks at the National Weather Service, they call this map the Cone of Uncertainty map.

KWONG: The Cone of Uncertainty doesn't really inspire a ton of confidence in me when I hear it. It literally has the word uncertain in it.

HERSHER: Well, that's the right way to react, actually, because you've hit on the problem with this map. The map does not show where the storm will go. It shows where the storm might go. And the cone that extends out from the storm, it represents where the center of the storm is likely to end up as the storm moves.

KWONG: OK. So where the center of the storm is likely to end up, that's a lot of caveats, you know?

HERSHER: (Laughter)

KWONG: That's very different than what I thought.

HERSHER: Yeah. So let's do a little test, here.

KWONG: OK.

HERSHER: Let's say you live in Miami, Fla., and you're looking at this Cone of Uncertainty map for Hurricane Duncan...

KWONG: (Laughter) OK.

HERSHER: ...And you see that the border of the cone comes near Miami, but it doesn't include Miami. Are you safe from Hurricane Duncan, Emily?

KWONG: Based on the tone in your voice, I am going to say, no.

HERSHER: Why not?

KWONG: Well, because the cone is just where the storm is likely to go, so it could shift direction and hit Miami.

HERSHER: Yes. That is one reason, correct. But there's actually a second reason. Remember, the cone is the likely path of the center of the storm. So you've dealt with the likely part of that sentence. I'm going to deal with the center of the storm part of the sentence. Because here's the thing - hurricanes can be huge, hundreds of miles across. So even if the path doesn't change, if Miami is right outside the cone on that map, you could still experience hurricane-force winds, flooding, the whole nine yards.

KWONG: Yikes. Yeah. So I can completely see people misunderstanding that. And does that misunderstanding happen a lot?

HERSHER: Yes. Totally. So, luckily, somebody has studied this. Unsurprisingly, that team of researchers is in Florida. Alberto Cairo and his colleagues at the University of Miami looked at how people interpret the Cone of Uncertainty map. And they found that people are really confused. They think they're safe when they're not. Some people misunderstand what direction the storm is going in. It's a mess.

ALBERTO CAIRO: Long story short, don't trust your first intuition. Don't trust your first take. Because probably if you just stare at it for a couple of seconds, you will get it wrong.

KWONG: Yeah. This is really important information. And your first piece of advice is to triple-check your assumptions about where the storm is going and whether you could be affected. Don't just take a quick glance at the map.

HERSHER: Exactly.

KWONG: OK. Great. What's next? Because personally, I would like to know what I'm supposed to do with that information - if I figured out that Hurricane Duncan is headed for my house in Miami.

HERSHER: So in order to figure out how to prepare, you need to know what hazards you're going to expect with the storm and which ones are the most dangerous to you, whether that's water coming from the ocean or rain or wind. And this is where you have got to go back to that Cone of Uncertainty map. That map is usually published with information about the storm's wind category.

KWONG: Right. And that's like if it's a Category 2 hurricane or Category 3 hurricane or whatever.

HERSHER: Exactly. The categories - they range from tropical storms with sustained wind below 74 miles an hour, up to Category 5 storms with sustained winds above 156 miles per hour. And that's all the categories mean.

KWONG: What?

HERSHER: I will say it again. That is all they mean. They do not tell you anything else about the effects of the storm.

KWONG: Oh, my God.

HERSHER: Which is a problem because although high winds can destroy buildings, water is the most deadly part of a hurricane. And a storms category doesn't tell you anything about flooding it will cause. It only tells you about wind.

KWONG: That is shocking to me. I had no - I had no idea. So this is lesson No. 2, I guess? Don't assume that a weaker storm - like tropical storm or Category 1 hurricane - isn't dangerous, 'cause those storms can still flood your house.

HERSHER: Exactly. And in recent years, we've seen storms like this. So Hurricane Harvey - when it hit Houston - was a tropical storm.

KWONG: Wow.

HERSHER: So don't count out the so-called weak storms. They can really mess you up. Or as Michael Brennan, the senior hurricane specialist at the National Hurricane Center, puts it...

MICHAEL BRENNAN: There's probably too much attention paid to the intensity of the storm. What are the peak wind speeds? While that's certainly a factor in what the impacts of the storm could be, it's the water hazards that kill the most people - primarily storm surge, but then also freshwater flooding.

KWONG: So, Becky, where can people get information about flood risks, specifically, from hurricanes?

HERSHER: So there are a few places. The National Weather Service does publish maps that show how much storm surge, like ocean water flooding they're predicting along the coast when a hurricane is approaching.

KWONG: OK.

HERSHER: That's a good place to start, especially if you live on the coast - makes sense. They also publish rain total predictions, especially as storms get closer to land. And that's a really important thing to look at if you live farther inland. Because especially with climate change, hurricanes can dump just massive amounts of rain really far inland.

KWONG: Right. And I feel like we've seen that a lot in recent years.

HERSHER: Yeah. Basically every year since 2017, there's been a hurricane that caused serious flooding because of rain - sometimes a really long way from where it came ashore. And one thing to remember here is that the information that's most helpful to you varies according to where you live, even for the same storm.

So here's an example. Hurricane Michael in 2018 - it had really strong winds and a lot of storm surge when it hit the Florida Panhandle. And that was devastating for cities and towns right on the coast. So if you lived there, storm surge and wind were important to you. But it also dropped a ton of rain all the way up in Virginia and caused serious flooding there too. So people living in those places, they needed to look for different information.

KWONG: Got it. But if you don't have a ton of time, like if you're looking to make a life-or-death decision in a pinch, where should you turn to first for this information? Should you just bookmark the National Weather Service website?

HERSHER: Yeah. So people - they can go directly to the National Hurricane Center website. That's part of the National Weather Service, or look at their social media accounts. That's a good way to get some of this information, especially the wind and storm surge information.

But for flooding from rain, in a lot of places local news and local emergency officials are going to be more accurate. And that's because they know the drainage systems for the local area, and they can help predict which places are in the most danger from water. And local news and local government are also good places look, because that's where the evacuation orders are going to come from if that's what's in the cards.

KWONG: I do like any story where the main takeaway is pay attention (laughter) to local news.

HERSHER: I know you do. Yeah, so that's true.

KWONG: (Laughter) That's very helpful. But what I still don't understand is actually why so much of this responsibility, this decision making falls on individuals? Like, why do I need to look multiple places to figure out if I'm in harm's way?

HERSHER: Yes. I also had this question. I think it's a good one. People who study how we communicate about hurricanes say that this is one of the most annoying things about the current system. Even though forecasters are putting out all kinds of information, it's still hard for regular citizens to use it easily.

One issue is that different people are in different amounts of danger. So for example, if you rely on electricity for a medical device, you might make a different choice when a hurricane is headed your way than someone with two little kids, let's say.

KWONG: Right.

HERSHER: But I did talk to Barbara Millet, the director of the University of Miami's User Experience Lab. And she studies hurricane forecasts products, like the Cone of Uncertainty. She said they've found that people definitely want clearer information.

BARBARA MILLET: The information that's being conveyed in these types of products does not necessarily speak to them about what they - what it is that they really need in order to make decisions - information like, am I in an evacuation zone? What types of things should I be doing? What are resources for me? Where is there a shelter? Should I be going - evacuating on a certain route versus another route? So that type of information is what they're looking for, but that's not necessarily being conveyed.

HERSHER: So there's definitely room for improvement. And actually, the National Hurricane Center is working with social scientists to study this exact thing - how to communicate hurricane risk better.

(SOUNDBITE OF MUSIC)

KWONG: Was that - did I just detect good news from Rebecca Hersher, climate reporter?

HERSHER: (Laughter) Oh, I forgot. I forgot what I actually want to tell you, which is that 2020 is on track to be the hottest year ever.

KWONG: Too much of a good thing, knew it. OK. Thanks, Becky Hersher, (laughter) for coming on SHORT WAVE.

HERSHER: Thanks.

KWONG: This episode was produced by Brit Hanson, edited by Viet Le and fact-checked by Berly McKoy. I'm Emily Kwong. Thanks for listening to SHORT WAVE From NPR.

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