Cone of Uncertainty: What It Actually Means

It's probably the hurricane season's most eagerly awaited piece of information for a brewing storm: the forecast path.

Sometimes called the "cone of uncertainty", it's a useful tool for tracking where a storm is headed, but there are some important things you might not know about it, including how it doesn't show the full scope of impacts.

(MORE: How Hurricanes Are Rated 1 To 5)

Big Picture

• Cone Only Shows Track Of Storm's Center: The cone represents the most probable track of the center of a tropical depression, tropical storm or hurricane over the next five days, assuming the storm lasts that long. It also has labels to show the general timing of the arrival of the storm's center, and in some cases, you will see the forecast wind intensity for those intervals.
• Cone Doesn't Show Impacts: A storm's impacts cannot be judged by just glancing at the forecast path. Impacts often happen well outside the cone, sometimes hundreds of miles from the center of the storm. That can include all impacts like flooding rainfall, storm surge, strong winds and tornadoes.
• Storm Impacts Outside Cone Case 1: In 2024, Hurricane Helene's forecast path correctly stayed west of the Tampa Bay region in the 48+ hours leading up to its landfall farther north in the Big Bend. However, a damaging storm surge still hit the Tampa area hard, killing 12 people in Pinellas County.

• Storm Impacts Outside Cone Case 2: In June 2017, the forecast path for Tropical Storm Cindy was pointed toward the Texas and Louisiana border. Wind shear caused the storm to be lopsided, allowing most of its impacts from heavy rain, coastal flooding and tornadoes to be felt much farther east, from southeast Louisiana to Mississippi, Alabama and the Florida Panhandle.

Deeper Dive

• How The Cone Is Formed: The forecast path is created by enclosing the area swept out by a set of circles (not typically seen on the graphic, but shown below) along with the forecast track at 12-hour and then 24-hour intervals. Each circle's size is set at two-thirds of the historical forecast error over the previous five-year period. The size of this cone does not change from one storm to the next, from one forecaster to the next, or during the storm's history.
• Storms Can Track Outside The Cone: Based on those previous forecast errors mentioned above, the entire track of the tropical cyclone can be expected to remain within the cone about 60 to 70 percent of the time. That's right – a storm's center doesn't always stay within the boundaries forecast several days in advance, which is why you should check frequently for possible shifts.
• Slow Storms Can Squish The Cone Into A Circle Shape: The cone becomes wider as the forecast uncertainty increases with time, carving out the cone shape. But, when a storm is stalled or is forecast to slow to crawl, it can cause the forecast timing intervals to stack up in close proximity, creating a cone that looks more like a circle, as seen in Harvey along the Texas coast in 2017.

More To Know

• The Cone Has Shrunk Significantly In Past 20+ Years: Compared to 2003, when the cone of uncertainty was first pushed out to five days, the radii that make up the cone are more than 100 statute miles smaller. The radius of the circle that made up the five-day forecast in that year was 371 miles compared to 245 miles in 2025.
• How Large Are Forecast Errors?: Due to increasingly accurate computer models and satellite data, forecast errors are gradually shrinking but remain fairly substantial, especially farther out in time. That's because some tropical storms and hurricanes are more difficult to forecast than others, due to uncertainties regarding steering winds and intensity. For the past five years, track errors have ranged from 30 statute miles at 12 hours to 245 miles at 120 hours (5 days), according to the National Hurricane Center.

Chris Dolce has been a senior digital meteorologist with weather.com for nearly 15 years after beginning his career with The Weather Channel in the early 2000s.