Why a Hurricane Forecast Cone Does Not Show Every Hazard
The National Hurricane Center cone describes uncertainty in the forecast track of a tropical cyclone’s center. It does not show the storm’s full size or the complete reach of wind, surge, rain and tornado hazards, as Hurricane Milton demonstrated when its wind field expanded approaching Florida.
Timeline
- 2024-10-05: Milton formed in the Gulf of Mexico and began the advisory sequence represented in NHC forecast graphics.
- 2024-10-08: NHC warned that Milton’s wind field was expanding and damaging wind, surge and heavy rain would extend outside the cone.
- 2026 season: NHC began testing an ellipse-based experimental cone alongside its operational product.
A hurricane forecast cone shows the probable path of the tropical cyclone’s center, not the outline of the storm and not a boundary between danger and safety. The National Hurricane Center builds the operational cone around forecast positions from 12 through 120 hours. Its width reflects recent historical track errors, so it grows farther into the future as uncertainty increases. A location outside the cone can still experience dangerous conditions. [1][2]
For the 2026 operational cone, NHC sets circles around forecast points so that two-thirds of official track errors from the preceding five-year sample fall within them, then joins those circles into a cone. This means the center historically falls outside the corresponding error area about one-third of the time. The center line is not a special corridor of certainty, and the cone does not assign zero risk to places beyond its edge. [1][2]
A tropical cyclone is much larger than its center. Tropical-storm-force and hurricane-force winds can extend far beyond the cone, and their reach can differ by quadrant. Storm surge depends on wind direction, coastline shape, storm size and timing. Heavy rain and tornadoes may occur well away from the eye. NHC therefore publishes separate wind-speed probabilities, arrival-time graphics, surge products, rainfall forecasts, watches, warnings and key messages that must be read with the track graphic. [2][3]
Hurricane Milton illustrated the limitation in October 2024. As the hurricane approached Florida, NHC said its wind field was expected to grow substantially and warned that damaging winds, life-threatening surge and heavy rainfall would extend well outside the forecast cone. The advisory discussion treated the center track, intensity and expanding wind field as related but distinct forecast problems. Looking only at whether a town sat inside the white cone would have discarded crucial hazard information. [4][5]
Some cone graphics add the current estimated wind extent and color-coded watches and warnings. Those layers are useful, but they still do not promise that every shaded location will experience the indicated sustained wind. The wind radii show a maximum reach within storm quadrants, while watches and warnings describe areas where conditions are possible or expected under official criteria. Users should read the advisory time because every layer changes as new observations arrive. [3][6]
Cone design can also evolve. During the 2026 season, NHC issued an experimental version built with ellipses that separately represent along-track speed error and cross-track direction error, while the operational cone retained the established circle-based method. The experimental design does not turn the cone into an impact map; it still communicates uncertainty about the center. Current NHC documentation should be checked each season because graphics and methodology may change. [1][7]
The safest reading sequence is to note the advisory time, understand the range of possible center tracks, and then consult the hazard-specific products and local instructions. Emergency decisions should follow official watches, warnings and evacuation orders rather than a visual judgment about the cone’s edge. Milton’s forecasts provide a concrete lesson: the cone answered where the center might go, while the wind, surge and rainfall products answered what communities might experience. [2][3][4]
Sources
- National Hurricane Center: Definition of the Track Forecast Cone
- National Hurricane Center: Forecast Cone Graphic Description
- National Hurricane Center: How to Use the Cone Graphic
- NHC Hurricane Milton Discussion 15
- NHC Hurricane Milton Forecast Advisory 13
- National Hurricane Center: Milton Graphics Archive
- National Hurricane Center: 2026 Experimental Cone