WEATHER NEWS: How Hurricane Ian’s “cone” of predicted path confused some Floridians
Its image is ubiquitous ahead of any hurricane, fundamental to decisions coastal residents, first responders and politicians make to prepare for storms and to evacuate: the forecast cone.
But amid finger-pointing over what mistakes may have contributed to dozens of deaths during Hurricane Ian, the concept of the cone is being questioned.
The National Hurricane Center graphic is perhaps misunderstood as widely as it is broadcast. It simply shows the likely future locations of a storm’s center — that is, the path weather-forecasting models suggest its eye will take over the next three to five days.
But many view the cone as indicating that danger is limited to areas within a shaded wedge of the map.
“Some people think the cone represents the size of the storm, which it doesn’t,” said Rebecca Morss, a senior scientist at the National Center for Atmospheric Research. “Some people think it represents the area of impact, which it doesn’t.”
Indeed, many residents and authorities have said Ian’s track surprised them, even though the cone for days included the storm’s eventual landfall point on its southern edge. So some meteorologists and social scientists are saying the disaster is only the latest evidence that the Hurricane Center should revamp the way it depicts forecasts — communicating the scope and intensity of a storm’s threats, rather than just the expected path of a single point at its center.
“The storm is not a point,” said Craig Setzer, a broadcast meteorologist in Miami. “As much as we have told people that hazards extend outside the cone, which is almost a disclaimer, people don’t perceive that.”
The cone fails to communicate threats such as storm surge — the destructive rise in water above normally dry land at the coast — as well as inland flooding, winds and tornadoes. This leaves people unprepared to make life-changing decisions to save their lives and protect their property, Morss said.
“As we saw in this case, sometimes you don’t realize how bad it is and it’s really too late to protect yourself,” she said.
That was true last week for many in communities such as Naples, where lifelong resident and charter boat captain Bill D’Antuono said many fixated on the center of the Hurricane Center’s forecast cone and early predictions of a strike near Tampa. When Ian inundated coastlines near Naples with as much as 12 feet of water, locals were stunned, and D’Antuono was frustrated.
The Hurricane Center has used the forecast cone since 2002 to show a zone where a storm’s center will probably pass. It begins at a tropical cyclone’s current location and widens over the course of its predicted track to reflect increasing uncertainty about the storm’s movement — it’s easier to forecast where a storm will be tomorrow than where it will be in three or five days.
The width of the cone is based on an average of forecast errors over the previous five years — that is, the difference between the Hurricane Center’s predictions of where a storm would go and the track it ultimately took.
But that means for storm tracks that are relatively easy for meteorologists to predict, the cone is wider than it needs to be; for hurricanes like Ian that are difficult to pin down, the cone is too narrow, underestimating risk to areas outside its boundaries. Forecast cone graphics also failed to capture the uncertainty in the tracks for Charley in 2004, Joaquin in 2015 and Matthew in 2016, meteorologists said.
The width of the cone at different lead times has gotten smaller over the years as forecasts have improved. Despite these gains, scientists have grappled with the cone’s effectiveness when communicating risk to the public.
“I think the limitations of the cone have been known since it was first used for communication, and NOAA’s been actively working on it to improve communication,” Morss said.
A key limitation is made clear in the fine print around the graphic. As Hurricane Ian approached landfall, a disclaimer appeared atop every six-hour update as it does for the forecast cone graphic for every storm: “Note:The cone contains the probable path of the storm center but does not show the size of the storm. Hazardous conditions can occur outside of the cone.”
But the disclaimer is often stripped off versions of the cone displayed on television, and research has repeatedly shown that a minority of people understand what the cone does and does not depict.
Of 2,847 Floridians surveyed, almost half incorrectly believed that areas outside of the cone were safe from hurricane damage, for example, while 40 percent thought the cone indicated where damage would occur, a study published in August reported.
Forty-eight percent believed the cone showed all possible paths the center of a storm could take — when, in reality, it can only be expected to include the most likely 60 to 70 percent of possible tracks. That means there is about a 1-in-3 chance a storm’s center could take a path outside the cone, something few people are aware of.
“You would think, as time goes on, more people would gradually learn,” said Brian McNoldy, a hurricane researcher at the University of Miami and study co-author. “But I don’t know if that’s happened.”
Instead, some scientists say changes are needed in how cone graphics are designed and shared — if not whether the cone should be used at all — to better communicate risks of flooding, damaging winds and tornadoes.
“I think this is one of the challenges, is to get people understand a hurricane is not a point on the map. It’s not like the center of circulation is the only thing: It is the impacts,” said W. Craig Fugate, who led the Federal Emergency Management Agency from 2009 to 2017.
Fugate wants to move away from solely relying upon the cone to track where the storm is going, and instead use a new model that would communicate the impacts more clearly to decision-makers and the public. For him, the question of how to communicate multifaceted weather risks is a complex issue that social scientists and meteorologists will have to figure out.
Many of them suggest misinterpretations could be avoided if forecast cone images did not include a centerline, for example, because it can give an undue impression of certainty in where a storm will strike. The line, and the cone itself, are based on predictions from weather forecasting models that are rarely perfect.
In the case of Ian, while forecast cones included the eventual landfall point Cayo Costa just west of Fort Myers, focus was largely on a centerline that suggested impact closer to Tampa until about 24 hours before the storm crashed ashore.
“People focus overly on the track line,” Morss said. “They don’t know that there’s potential for tracks outside the cone itself.”
Beyond that, there is a need to communicate that a storm will be felt far away from its center. Research shows that tropical-storm-force winds of 39 to 73 mph are all it takes for people to perceive that they have been “hit” by a storm, Setzer said. In the case of Ian, hurricane-force winds of at least 74 mph spanned nearly 100 miles at landfall, andtropical-storm-force winds extended virtually the length of the Florida Peninsula.
The Hurricane Center develops a host of graphics communicating how widely hurricane- and tropical-storm-force winds may be felt, and to what extent of coastline a storm can be expected to deliver storm surge. But none are shared as widely as the forecast cone.
“People don’t have time to look at 10 different things,” Morss said. “Those can be difficult to interpret, as well.”
Studies show that during times of extreme weather events, people flock to broadcast airways for information. The national media’s hyper-focus on where storms are tracking also draws extra attention to the cone, rather than to other forecast graphics and tools the National Weather Service uses, Fugate said.
Instead, it would be more helpful if cone graphics included areas of potential impact and types of hazards to expect, experts said, not just a prediction of where a storm’s center will go. As it is, the cone doesn’t reflect much beyond that.
“The cone is doing what the cone is supposed to do,” Setzer said. “The storm is much bigger than a point.”
Susan Buchanan, a spokesperson for the National Weather Service, which oversees the Hurricane Center, said that “we frequently adapt our products, services and communications based on social science guidance,” but did not offer any specific information about plans to update the forecast cone.