\n<\/p>\n
If you\u2019ve ever taken even a cursory glance at a hurricane forecast, you\u2019ve seen some version of the \u201ccone of uncertainty.\u201d It sounds like some other-dimensional realm of indecision, but it\u2019s a mainstay for communicating hurricane forecasts. Though these maps pack in plenty of valuable information, it can be a bit tricky to interpret them if you don\u2019t know exactly what you\u2019re looking at.<\/p>\n
Here Scientific American walks you through all the forecast components and what they mean\u2014and, almost as crucially, what they don\u2019t. We also point you to some other resources that are often the most helpful for those staring down an approaching storm.<\/p>\n
If you’re enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.<\/p>\n
Above is an example of what you might see if you visit the National Hurricane Center\u2019s (NHC\u2019s) website during a storm in progress\u2014in this case it\u2019s an archived forecast from 2024\u2019s Hurricane Milton. Various broadcasters, news sites and other groups that cover the weather often have their own versions of this map. There\u2019s a lot happening here, so let\u2019s break things down piece by piece.<\/p>\n
First off, because the cone-of-uncertainty graphic is a depiction of a forecast, it\u2019s looking into the future. Each update to the map shows the storm\u2019s current location, then roughly where the center of the storm will be over the next three to five days (depending on which version you are looking at).<\/p>\n
This is the centerpiece of the graphic\u2014the actual cone of uncertainty\u2014so called because it is an indicator of the possible error range in that forecast of where a tropical storm or hurricane is headed.<\/p>\n
The first key point in understanding the cone is that the error isn\u2019t based on the specific storm forecast; rather, it\u2019s an average of the overall forecast error over the past five years. So the more forecasts improve, the narrower the cone gets. The cone gets its shape because \u201cthe uncertainty increases with time,\u201d says Brian McNoldy, a hurricane researcher at the University of Miami. It\u2019s easier to forecast the near future than several days out.<\/p>\n
And because the error is based on that long-term forecast average, \u201cyou get the exact same cone all year long for every storm,\u201d McNoldy says. It can appear different\u2014for example, more squat or elongated\u2014because of how fast or slow the storm is going.<\/p>\n
The cone is meant to encompass where a storm actually goes two thirds of the time, so \u201cthe cone is designed to fail one third of the time,\u201d says James Franklin, former chief of the NHC\u2019s Hurricane Specialist Unit. So two thirds of the time, the storm will follow some path within the cone, but about one third of the time, its center will venture outside of the cone as the storm progresses. This is one reason why you never want to assume that because you\u2019re just outside of the cone, you\u2019re in the clear.<\/p>\n
The other reason is that the cone only tracks the path of the storm\u2019s center\u2014it does not mean the storm\u2019s impacts are limited to the area of the cone. \u201cIt isn\u2019t accounting for how big the storm is,\u201d or if a storm\u2019s winds and rains are concentrated on one side, says Kim Wood, an atmospheric scientist at the University of Arizona. \u201cIt really makes no sense to look at the cone, see that you\u2019re outside of it and then ignore everything else,\u201d Franklin says.<\/p>\n
The map also includes the expected form of the storm at various points in the future, which are denoted with black or white circles and letters. The letters show whether a storm will be a tropical depression (D), tropical storm (S), hurricane (H) or major hurricane (M). (A major hurricane is a Category 3 or higher on the Saffir-Simpson scale.)<\/p>\n
A black circle means the storm is a tropical cyclone, or one that derives its strength from heat-driven convection at its core. A white circle denotes a potential tropical cyclone (one that could become a tropical cyclone) or a former one\u2014often a storm that is now extratropical, meaning it is driven more by a temperature difference across a weather front than by convection.<\/p>\n
READ MORE: Hurricane Science Has a Lot of Jargon\u2014Here\u2019s What It All Means<\/p>\n
There are also color-coded indicators of hurricane and tropical storm watches and warnings.<\/p>\n
But these indicators are only based on a storm\u2019s wind speeds\u2014they don\u2019t suggest anything about potential storm surge, rainfall or tornadoes, all of which can be threats from tropical cyclones.<\/p>\n
NHC forecasts\u2014including the cone of uncertainty graphic\u2014are useful, but they are intended mostly for other meteorologists and emergency managers that use that information to make more detailed local forecasts and decisions about where people should evacuate or position supplies. \u201cThe NHC is not issuing information for a person,\u201d Wood says.<\/p>\n
Some researchers have explored making versions of the cone that are more useful for communicating threats. A 2019 study found that people estimated more damage from a hurricane when a forecast track went over a location than when it didn\u2019t. The researchers suggested that forecasts should show more hurricane paths to convey the uncertainty in where a hurricane would go.<\/p>\n
The graphic above is an example of such a visualization. It shows that the forecast is more certain in the near future and that paths at the outside of the cone are less likely than those at the center\u2014but still possible.<\/p>\n
The cone graphic as it exists now can still be useful when looking out four or more days before a storm might arrive to get a general sense of where it is now and where it is going\u2014for example, if a storm in the Gulf of Mexico looks likely to curve into Florida, people in New Orleans may not need to be as alert. \u201cIt can be a decent starting point in just getting oriented into what the threat might be,\u201d Franklin says. \u201cIt\u2019s a good place to start, but you don\u2019t want to stop there.\u201d<\/p>\n
So where should you go for more useful hurricane information? Paying attention to a trusted local weather source, such as your local National Weather Service office, is generally the best bet for keeping up with impacts specific to your area and what steps need to be taken, such as whether to evacuate.<\/p>\n
The NHC also has maps that show when tropical-storm- and hurricane-force winds are likely to arrive at given locations and detailed maps showing expected storm surge levels. Much of this information is pulled together on the National Weather Service\u2019s Hurricane Threats and Impacts Tool, as well. This interactive map overlays the cone of a storm on top of wind, tornado, storm surge and rain threat information. You can click a given location and it will tell you what hazards you need to be concerned about.<\/p>\n
One of the most important things to remember no matter what forecast you\u2019re looking at is that forecasts change. Small variations in the storm itself or the larger atmospheric patterns can shift a storm\u2019s path or intensity.<\/p>\n
Human brains can naturally fall prey to the \u201canchoring effect\u201d\u2014we can become mentally rooted in one specific forecast and base our decisions on it rather than updating our thinking as conditions change. Maybe there\u2019s a particularly ominous forecast or a particularly good one for your location, \u201cand then you don\u2019t keep looking for updates,\u201d McNoldy says. But checking for updates is crucial to get ready for the coming storm.<\/p>\n","protected":false},"excerpt":{"rendered":"
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