Intensity changes in landfalling typhoons are of great concern to East and Southeast Asian countries 1 . Regional changes in typhoon intensity, however, are poorly known owing to inconsistencies among di erent data sets 2-8 . Here, we apply cluster analysis to bias-corrected data and show that, over the past 37 years, typhoons that strike East and Southeast Asia have intensified by 12-15%, with the proportion of storms of categories 4 and 5 having doubled or even tripled. In contrast, typhoons that stay over the open ocean have experienced only modest changes. These regional changes are consistent between operational data sets. To identify the physical mechanisms, we decompose intensity changes into contributions from intensification rate and intensification duration. We find that the increased intensity of landfalling typhoons is due to strengthened intensification rates, which in turn are tied to locally enhanced ocean surface warming on the rim of East and Southeast Asia. The projected ocean surface warming pattern under increasing greenhouse gas forcing suggests that typhoons striking eastern mainland China, Taiwan, Korea and Japan will intensify further. Given disproportionate damages by intense typhoons 1 , this represents a heightened threat to people and properties in the region.Tropical cyclones (TCs) cause devastating losses of life and property, and have major social and economic impacts around the world 1 . Given that nearly all the damage is associated with TC landfalls, and that the population of coastal areas is growing and sea level is rising, detection, attribution and prediction of regional changes in TC activity (especially intensity and frequency) are among the top priorities of TC research 9,10 . For the northwest Pacific, where TCs are most active and threaten a large population of East and Southeast Asia, progress in studying regional changes in TC intensity has been hindered by a lack of consensus on intensity changes among different TC data sets 2-8 . Particularly, under debate are historical changes in the annual counts of category 4-5 typhoons: the Joint Typhoon Warming Center (JTWC) and the Japan Meteorological Agency (JMA) TC data-the two most widely used data sets in typhoon research-show contradictory trends for the period starting from 1977 2,3,6,7 .The discrepancies in the TC intensity estimated independently by the two operational agencies can be reconciled by considering changes in the JMA methodology (see Methods). The adjusted JMA and JTWC data sets consistently show that the annual number of category 4-5 typhoons has increased by more than two over the past 38 years (from less than five per year to around seven per year), and the correlation coefficient between the two time series rises from 0.09 to 0.87 after the adjustment (Fig. 1a). Strikingly, the proportion of these intense typhoons to all typhoons has more than doubled, and the annual mean typhoon lifetime peak

During the past several decades operational forecasts of tropical cyclone (TC) tracks have improved steadily, but intensity forecast skills have experienced rather modest improvements. Here we use 40 years of TC track data to show that storm intensity correlates with translation speed, with hurricanes of category 5 moving on average 1 m s−1 faster than tropical storms. This correlation provides evidence that the translation speed of a storm can exert a significant control on the intensity of storms by modulating the strength of the negative effect of the storm‐induced sea surface temperature (SST) reduction on the storm intensification (i.e., the SST feedback): Faster‐moving storms tend to generate weaker sea surface cooling and have shorter exposure to the cooling, both of which tend to weaken the negative SST feedback. Consistently, there exists a minimum translation speed for intensification and its value grows with TC intensity, resulting in a minimum translation speed for the existence of a TC in each intensity category. Furthermore, a composite analysis of satellite‐based SST measurements reveals that in the tropical region the average strength of the storm‐induced sea surface cooling can be explained by the superposition of an effect due to the storm intensity and an effect associated with the translation speed, and implies that the variability of upper ocean stratification may not be an important factor in this region. Our results suggest that progress in the prediction of TC tracks, particularly in the translation speed of storms, should lead to improved storm intensity prediction.

The spatial structure and temporal evolution of the sea surface temperature (SST) anomaly (SSTA) associated with the passage of tropical cyclones (TCs), as well as their sensitivity to TC characteristics (including TC intensity and translation speed) and oceanic climatological conditions (represented here by latitude), are thoroughly examined by means of composite analysis using satellite-derived SST data. The magnitude of the TC-generated SSTA is larger for more intense, slower-moving, and higher-latitude TCs, and it occurs earlier in time for faster-moving and higher-latitude storms. The location of maximum SSTA is farther off the TC track for faster-moving storms, and it moves toward the track with time after the TC passage. The spatial extension of the cold wake is greater for more intense and for slower-moving storms, but its shape is quite independent of TC characteristics. Consistent with previous studies, the calculations show that the mean SSTA over a TC-centered box nearly linearly correlates with the wind speed for TCs below category 3 intensity while for stronger TCs the SSTA levels off, both for tropical and subtropical regions. While the linear behavior is expected on the basis of the more vigorous mixing induced by stronger winds and is derived from a simple mixed-layer model, the level-off for intense TCs is discussed in terms of the dependence of the maximum amplitude of the area-mean SSTA on TC translation speed and depth of the prestorm mixed layer. Finally, the decay time scale of the TC-induced SSTA is shown to be dominated by environmental conditions and has no clear dependence on its initial magnitude and on TC characteristics.

Ocean warming is a predicting factor for typhoon intensity.