Forward-Only Temporal-Coherence Occupancy Regimes in Atlantic Tropical Cyclone Intensity Evolution (1851–2024)

Nathan Howell 

Rapid intensification (RI) remains one of the most consequential and difficult-to-characterize aspects of tropical cyclone intensity evolution, commonly defined as an increase in maximum sustained wind speed of at least 30 kt within 24 h (Kaplan and DeMaria 2003; Kaplan et al. 2010; DeMaria et al. 2021). This study asks whether Atlantic best-track intensity records contain forward-detectable temporally coherent states that persist over time and whether cumulative occupancy of those states redistributes conditional RI occurrence. A minimal diagnostic is constructed from HURDAT2 using causal rolling means of maximum sustained wind speed across multiple advisory-window lengths and a common-sign temporal-coherence detector. The framework is evaluated under replay-constrained execution and frozen parameter governance using only current and prior intensity values from 1,991 Atlantic tropical cyclones during 1851–2024.

Storms spending longer cumulative time in the coherence state form a subset with elevated conditional RI occurrence. Conditional RI occurrence increases from a basin-wide baseline of approximately 26% to about 60% for storms with at least 140 h of coherence state and to about 67% for storms with at least 168–270 h of active state. Diagnostic behavior is additionally characterized using occupancy climatology, lifecycle-relative onset structure, and lead-time survival analysis. Alignment significance is evaluated against autocorrelated block-shuffle and phase-constrained null frameworks designed to preserve storm lifecycle evolution.

Temporal-coherence behavior remained stable across parameter neighborhoods, preserved timing organization under constrained null frameworks, and retained separable timing structure under tested conditioned formulations, although advisory-level occupancy coefficients attenuated substantially in shared-sample models. These results support interpretation of the diagnostic as a forward-only temporal-coherence framework, with occupancy providing the cumulative duration of the detected coherent state.