How Much Does Tropical Cyclone Rainfall Scale with Temperature? A Re-analysis of Ali et al. (2026) for the North Atlantic, 2015–2024

Ali et al. (2026) reported that heavy-precipitation intensity in North Atlantic tropical cyclones (TCs) rises by a median of 21% per kelvin of local dewpoint, about three times the Clausius–Clapeyron (CC) rate of ~7%/K. The scaling is "apparent": it is estimated by pooling storm time steps across storms, places and seasons, not from change over time. I rebuilt the analysis from public data (IBTrACS, ERA5, IMERG V07) for 172 storms and 3,006 TC time steps in 2015–2024 and tested it in four ways, with confidence intervals from a bootstrap over storms. (1) The paper's binned method gives 12.3%/K [9.2, 15.4] for dewpoint; the published 21.3%/K lies outside this interval, as do the published air-temperature and SST rates. (2) Dewpoint measured under the heavy rain or at the storm centre gives 12.7–17.8%/K; dewpoint in the storm environment gives 9.0 [6.0, 11.3]%/K. (3) Controlling for latitude, intensity and translation speed reduces the pooled log-linear estimate from 9.9 to 7.3%/K, and comparing time steps within the same storm reduces it to 1.7 [−2.1, 5.3]%/K. (4) Warmer-than-usual SST for a given place and season shows no detectable effect (0.7 [−7.6, 9.9]%/K), and storm rain intensity shows no trend over the decade. The super-CC rate is therefore a between-storm (cross-sectional) association. It does not show that warming makes a given storm rain harder at 21%/K, and the data are consistent with near- or sub-CC scaling once storm-to-storm differences are removed.