Extended Data Fig. 1: Maps of the occurrence frequency of intense TCs and the inter-seasonal difference between the early and late seasons.

a, Distribution of the track density of intense TCs (shading) and the location of RI events (dots) over the North Atlantic basin during 1981–2017. b, Linear trends of the inter-seasonal difference in intense TC number between the early and late seasons (also part of Fig. 1c). The black crosses indicate significance at the 95% confidence level. The annual number of intense TCs is calculated over 5° × 5° boxes prior to computing trends. The basemaps in panels a and b were plotted using the Matplotlib basemap toolkit⁷⁶ with the geographical coordinate system World Geodetic system 1984 generated by the Global Positioning System (maintained by the National Oceanic and Atmospheric Administration).