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Definition of the NHC Track Forecast Cone

Definition:

The cone represents the probable track of the center of a tropical cyclone, and is formed by enclosing the area swept out by a set of circles (not shown) along the forecast track (at 12, 24, 36, 48, 60, 72, 96, 120 hours). The size of each circle is set so that two-thirds of historical official forecast errors over a 5-year sample fall within the circle. The circle radii defining the cones in 2026 for the Atlantic, Eastern North Pacific, and Central North Pacific basins are given in the table below.

Radii of Atlantic and Eastern/Central Pacific forecast cone circles for 2026, based on error statistics from 2021-2025:

Forecast Period (hours)	2/3 Probability Circle, Atlantic Basin (nautical miles)	2/3 Probability Circle, Eastern and Central North Pacific Basin (nautical miles)
12	25	25
24	39	37
36	49	48
48	62	56
60	77	66
72	95	78
96	134	106
120	200	138

Example Graphic of 5-Day Track Forecast Cone:

Tropical Cyclone Track and Watches/Warnings
image example for Hurricane Helene