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1. Introduction

The rate of tropical cyclone (TC) intensification is dependent upon the interaction of convective-scale processes with the surrounding synoptic-scale environment. Considering the complexities involved in such multiscale interactions, improvements in TC intensity prediction have been challenging. Although operational TC intensity forecasts have experienced gradual improvements over recent years (e.g., DeMaria et al. 2014), TC intensity prediction remains especially challenging during events of TC rapid intensification (RI; Elsberry et al. 2007; Sampson et al. 2011; Kaplan et al. 2015; Emanuel and Zhang 2016). As seen in Fig. 1, operational, 24-h TC intensity forecasts for RI episodes [those with 24-h TC intensification rates of at least 25 kt (1 kt ≈ 0.5144 m s−1)] in the North Atlantic basin are associated with significantly larger errors than non-RI episodes over the last 20-30 years. Additionally, the trend lines in Fig. 1 indicate only small improvements in these forecasts due, in part, to the complexities arising from the multiscale nature of RI. Compounding these issues, TCs that rapidly intensify can be particularly dangerous and costly, as research has shown damages associated with TC landfalls display a power-law dependence on the maximum, sustained 10-m wind speed (Pielke 2007). Accordingly, the National Hurricane Center has made the accurate prediction of episodes of RI one of its top forecast priorities (Rappaport et al. 2012).

Fig. 1. Time series of operational, mean absolute intensity error (kt) from forecasts issued by the National Hurricane Center (NHC) for overwater 24-h intensity forecasts for TCs in the North Atlantic basin from 1990 to 2016. Error is shown for RI episodes (red), non-RI episodes (blue), and all intensity change episodes (black). RI episodes are defined as those with a 24-h change in maximum sustained 10-m winds ≥ 25 kt. Linear trends are indicated by the dashed lines.

Previous work has shown the likelihood of a TC to undergo RI is strongly linked to the prevailing environmental conditions (Kaplan and DeMaria 2003; Kaplan et al. 2010; Rozoff and Kossin 2011; Kaplan et al. 2015; Rozoff et al. 2015). Specifically, RI events are more likely to occur in environments characterized by weak vertical wind shear, a moist troposphere, high oceanic heat content, and upper-tropospheric divergence (Kaplan and DeMaria 2003; Kaplan et al. 2010; Rozoff and...

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