When is a major hurricane decided?
Two clocks
Three ways a storm's story ends
Schematic. Intensity (line) against the runway of major-capable open ocean (band); the dashed line is 96 kt. Shares are for 1979–2025 hurricanes.
What can be known, and when
How well each body of information picks the future majors at genesis
Held-out AUC (0.5 = coin flip, 1 = perfect), five-season holdouts, 4,500+ storms 1979–2025. The last bar uses hindsight: the runway the storm actually got.
Why near-misses stop with open water ahead
Where they stopped, and where majors kept going, over the ocean's stored heat
Dots: each near-miss at its peak (top) and each future major at the moment it passed the same wind (bottom). Shading: peak-season tropical-cyclone heat potential, ORAS5 1979–2025 (Aug–Oct north, Jan–Mar south; 1° grid, lightly smoothed). Hover a dot for its own heat content.
The same wind, a day either side
Medians, 630 near-misses (peak 64–95 kt with at least a day of major-capable ocean still ahead) and 1,135 future majors at the same wind. ERA5 at the exact hour; ocean heat from ORAS5.
The road ahead, mapped
Where storms are born, colored by how long their runway lasted
Every genesis 1979–2025. Runway: days until landfall, 45° latitude, or potential intensity falls below major strength for 12 h (open-ended where the track ended first).
Does a storm's peak scale with its ceiling?
How much the peak rises for each 1% rise in potential intensity
Elasticity of the population's peak to PI in a two-clock model fitted to 1979–2025 storms. Bars span the estimates of the external-clock ratio r (); blue: the seed is a fixed share of PI; orange: the seed is a fixed wind. 1.0 is one-for-one.
What's next
Full analysis, methods and every number: When Is a Major Hurricane Decided? →
Does warmer water make stronger hurricanes? Michaels (2006) and Emanuel (2007), re-run to 2026: Twenty years on →
1 · The population
Half the hurricanes, four-fifths of the energy
What separates a major from a hurricane that stayed minor
Mann–Whitney AUC per descriptor: 0.5 = no information; >0.5 = majors higher; <0.5 = majors lower. Colored by causal standing.
2 · Born lower, driven farther
The genuine precursors
3 · The gate
No rapid intensification, (almost) no major
4 · The environment null
Same ceiling, different conversion
When the majors happen
Month of lifetime-maximum intensity: majors vs hurricanes that stayed minor, 1979–2025.
5 · Timing
Concentrated in peak season, and not arriving earlier
6 · Change within the majors
The runway is shortening
7 · The ignition question
Do disturbances wait to catch fire?
The RI gate invites a mechanism hypothesis: perhaps what has changed is the incubation — the tropical-wave and depression stage — so that incipient vortices are more robust, or better positioned, before rapid intensification ignites. Split every hurricane's lifecycle at its first RI onset (first 6-h fix beginning a ≥30-kt/24-h rise) and the hypothesis becomes four measurements: the intensity at ignition, the incubation time (first 34-kt fix → ignition, an anchor insensitive to designation practice), the climb time (ignition → peak), and the thermodynamic ceiling at the moment of ignition against the storm's own track average.
The two-stage burner: where the climate signal enters, and where it does not
Conceptual model, with every element carrying its measured value and trend.
Where rapid intensification ignites, then and now
8 · What's special
The synthesis
Method
References
- Maue, R. N. (2026). Global Climatology of Tropical Cyclone Power Dissipation — the aggregate record; §8 for the exposure/track findings this paper's synthesis rests on.
- The Storm Ledger — the per-storm characteristics, families, and four-voice audit underlying every comparison here; full CSV there.
- Carrasco, C. A., Landsea, C. W. & Lin, Y.-L. (2014). The influence of tropical cyclone size on its intensification. Wea. Forecasting 29, 582–590.
- Kaplan, J. & DeMaria, M. (2003). Large-scale characteristics of rapidly intensifying tropical cyclones in the North Atlantic basin. Wea. Forecasting 18, 1093–1108. (the RI definition)
- Emanuel, K. (2000). A statistical analysis of tropical cyclone intensity. Mon. Wea. Rev. 128, 1139–1152. (the uniform-fate view this paper's runway result refines)
- Wang, S., et al. (2023). Seasonal advance of intense tropical cyclones in a warming climate. Nature 623, 83–89. (the advance tested — and not found — in §5)
- Gilford, D. M. (2021). pyPI v1.3. GMD 14, 2351–2369. (the PI record of §4)