Millions of coastal residents scanning hurricane forecast graphics this season will see a noticeably larger shaded zone around a storm’s projected path. The National Hurricane Center has introduced an experimental cone that replaces the traditional circles, built from the 67th percentile of past track errors, with wider ellipses drawn from the 90th percentile of along-track and cross-track errors. The shift, grounded in five years of forecast verification data covering 2021 through 2025, is designed to show communities that tropical-storm-force winds can reach well beyond the predicted center track. For households that previously fell just outside the old cone and skipped preparation, the change could redefine who takes action and when.
Why a wider cone changes the calculus for coastal residents
The traditional cone of uncertainty was never meant to capture every possible outcome. Its circles were sized so that roughly two-thirds of historical official forecast errors fell within them, according to the National Hurricane Center’s cone description. That left about one in three storms tracking outside the shaded area at any given lead time. Residents who saw their county sitting just beyond the cone’s edge often treated that boundary as a safety line, choosing not to evacuate or stock supplies.
The experimental graphic addresses that gap directly. By switching to the 90th percentile of along-track and cross-track errors, the new ellipses capture a much larger share of possible storm positions. The practical effect is that communities 50 or 100 miles from the forecast center, places that previously appeared “safe” on the old map, now fall inside the shaded zone. Emergency managers have long warned that the cone’s edges are not walls, but the visual shorthand encouraged exactly that interpretation.
Whether the wider graphic actually changes behavior is an open question. One testable prediction: if the expanded cone works as intended, counties that sit between the old 67th-percentile boundary and the new 90th-percentile boundary should show higher rates of evacuation compliance and supply purchases during the first storms of the 2026 season compared with similar counties in prior years. County-level retail and shelter data from the Federal Emergency Management Agency and private-sector trackers could confirm or reject that hypothesis within two hurricane seasons.
How the 90th-percentile ellipses differ from the old circles
The mechanical change is straightforward but significant. The operational cone has historically used circles at each forecast lead time. Each circle’s radius comes from the absolute track errors recorded over the previous five years, set at the 67th percentile so that two-thirds of past forecasts would have placed the actual storm center inside the circle. The National Hurricane Center’s experimental cone page explains that the new approach replaces those circles with ellipses. Ellipses account for the fact that forecast errors are not symmetric: storms tend to run ahead of or behind their predicted position (along-track error) at different rates than they drift left or right (cross-track error). Drawing the ellipse at the 90th percentile means nine out of ten historical storms would have had their center fall inside the shape at the corresponding lead time.
The 2026 cone radii table draws on error statistics from the 2021 through 2025 seasons. The NHC maintains a formal forecast verification program that publishes annual reports and official five-year mean errors, providing the raw data behind both the old circles and the new ellipses. Because forecast skill has generally improved over time, the five-year rolling window keeps the cone calibrated to current model performance rather than outdated accuracy levels.
The shape change also carries a communication benefit. Circles imply equal uncertainty in every direction, which does not match reality. A hurricane approaching the Gulf Coast, for example, may have tighter cross-track certainty but wider along-track uncertainty depending on steering currents. Ellipses let the graphic reflect that asymmetry, giving viewers a more honest picture of where the storm could arrive and when. In practice, this means a storm could be depicted as more likely to arrive earlier or later than expected while still having relatively narrow left-right spread, or vice versa.
For forecasters, the ellipse structure also aligns better with how numerical models actually behave. Ensemble guidance often shows elongated clusters of possible storm centers stretching along the direction of motion, not neat circular clouds. Translating that pattern into an ellipse, even one derived statistically rather than drawn directly from each model run, makes the official product more consistent with the underlying science without overwhelming the public with raw spaghetti plots.
Gaps in the evidence and what to watch this season
Several pieces of the puzzle are still missing. The NHC has published the statistical framework and the 2026 radii table, but the raw error-distribution datasets used to calculate the 90th-percentile ellipse dimensions have not been released for independent review. Outside researchers can verify the general approach through the verification program’s published mean errors, yet reproducing the exact ellipse sizes requires granular data that remains internal.
No public-survey data exists on how residents actually interpret the wider cone. Behavioral research on hurricane graphics has shown that people often confuse the cone’s size with a storm’s wind field or intensity, reading a larger shaded area as a stronger hurricane rather than a broader range of possible tracks. If that misperception carries over to the new ellipses, the wider graphic could trigger unnecessary panic in areas far from the likely path while failing to convey the intended message about residual risk.
Emergency managers face a resource question as well. A larger warning footprint could strain shelter capacity, fuel supply chains, and contraflow highway plans if more counties activate evacuation orders simultaneously. Officials must balance the benefits of earlier, broader alerts against the costs of mobilizing people and equipment that may ultimately not be needed. Over time, if too many communities inside the expanded cone experience little impact, residents may begin to discount the warnings, a phenomenon sometimes described as “warning fatigue.”
The first real test will come when a named storm threatens the U.S. coastline this season. At that point, the gap between the old and new cone boundaries will no longer be an abstraction; it will map onto real neighborhoods deciding whether to board up windows, move boats, or leave town. Researchers and emergency managers will be watching several indicators closely: whether people in the newly shaded areas report higher awareness of their risk, whether evacuation orders are more closely aligned with the expanded cone, and whether confusion about the graphic’s meaning increases or decreases.
In the meantime, the NHC and local partners are likely to emphasize a simple message: the cone is a tool for tracking the storm’s center, not a map of where impacts will occur. Tropical-storm-force winds, storm surge, and flooding rains can extend far outside any cone, circular or elliptical. The experimental change to 90th-percentile ellipses makes that point visually harder to ignore, but it does not replace the need for residents to follow local instructions, monitor updated advisories, and focus on hazard-specific products such as wind and surge maps. Whether the wider cone ultimately saves lives will depend less on its geometry than on how well those messages land when the next hurricane comes ashore.
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*This article was researched with the help of AI, with human editors creating the final content.
