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This study examines the interdecadal variations in the frequency and intensity of tropical cyclones (TCs) making landfall in South China (SC) during the period 1975–2018. The annual frequency shows a decrease in 1997 but rises again since 2008 and the annual maximum landfall intensity (MLI) shows an increase since 2012. According to these variations, three subperiods, 1975–1996 (higher frequency but lower MLI), 1997–2011 (lower frequency and MLI) and 2012–2018 (higher frequency and MLI), are defined. The increase in MLI during 2012–2018 is related to the increases in the frequency of (1) TCs undergoing rapid intensification over the South China Sea (SCS) and landfalling in SC, with higher maximum intensity and location of maximum intensity closer to the coast of SC, and (2) intense typhoons (ITYs) over the western North Pacific (WNP), which maintain high intensity before landfall. These changes are closely related to the lower vertical wind shear and higher TC heat potential over the ocean east of the Philippines and the northern part of the SCS. Such an environment is more conducive for TC intensification, leading to the observed increases in the number of rapid-intensifying TCs over the SCS and ITYs over the WNP. Some of these latter TCs move across the SCS and tend to maintain high intensity during landfall in SC. The steering flow also changes, which allows more TCs to enter the SCS, resulting in an increase of ITYs making landfall in SC.

Slow-moving tropical cyclones (TCs) can cause heavy rain because of their duration of influence. Combined with expected increase in rain rates associated with TCs in a warmer climate, there is growing interest in TC translation speed in the past and future. Here we present that a slowdown trend of the translation speed is not simulated for the period 1951–2011 based on historical model simulations. We also find that the annual-mean translation speed could increase under global warming. Although previous studies show large uncertainties in the future projections of TC characteristics, our model simulations show that the average TC translation speed at higher latitudes becomes smaller in a warmer climate, but the relative frequency of TCs at higher latitudes increases. Since the translation speed is much larger in the extratropics, the increase in the relative frequency of TCs at higher latitudes compensates the reduction of the translation speed there, leading to a global mean increase in TC translation speed. How the translation speed of tropical cyclones has changed in recent decades and will change in the future has been the subject of debate. Model results show that on average, they have not slowed down in the past, but despite a slowing of tropical cyclones at higher latitudes, a poleward shift in their mean track location causes a general speed up under high greenhouse gas emissions.

In general, tropical cyclone (TC) rainfall accumulation usually decreases with faster TC translation speed but increases with heavier rain rate. However, how the TC rain rate changes with translation speed is unclear. Here we show that, in all TC basins, the average TC rain rate significantly increases with translation speed. On average, the rain rate in a fast-moving TC is 24% higher than in a slow one. This difference increases with TC intensity, with category 3–5 TCs having a 42% increase while tropical depressions exhibit only a 9% increase. The increase in the average TC rain rate with translation speed is mainly caused by the TC net inflow in the lower troposphere, as well as vertical wind shear. These findings have important implications not only for a deeper understanding of rain rate changes in a translating TC but also for short-term forecasts of TC rainfall and disaster preparedness. Using satellite observations, the authors show that the average tropical cyclone (TC) rain rate increases significantly with translation speed. On average, the rain rate of a fast-moving TC is about 24% higher than that of a slow one.

Tropical cyclone (TC) activity over the western North Pacific (WNP) exhibits a significant interdecadal variation during 1960–2011, with two distinct active and inactive periods each. This study examines changes in TC activity and atmospheric conditions in the recent inactive period (1998–2011). The overall TC activity shows a significant decrease, which is partly related to the decadal variation of TC genesis frequency in the southeastern part of the WNP and the downward trend of TC genesis frequency in the main development region. The investigation on the factors responsible for the low TC activity mainly focuses on the effect of vertical wind shear and subtropical high on multidecadal time scales. A vertical wind shear index, defined as the mean magnitude of the difference of the 200- and 850-hPa horizontal zonal winds (10°–17.5°N, 150°E–180°) averaged between June and October, is highly correlated with the annual TC number and shows a significant interdecadal variation. Positive anomalies of vertical wind shear are generally found in the eastern part of the tropical WNP during this inactive period. A subtropical high area index, calculated as the area enclosed by the 5880-gpm line of the June–October 500-hPa geopotential height (0°–40°N, 100°E–180°), shows a significant upward trend.A high correlation is also found between this index and the annual TC number, and a stronger-than-normal subtropical high is generally observed during this inactive period. The strong vertical wind shear and strong subtropical high observed during 1998–2011 together apparently lead to unfavorable atmospheric conditions for TC genesis and hence the low TC activity during the period.

Heavy rainfall is one of the major aspects of tropical cyclones (TC) and can cause substantial damages. Here, we show, based on satellite observational rainfall data and numerical model results, that between 1999 and 2018, the rain rate in the outer region of TCs has been increasing, but it has decreased significantly in the inner-core. Globally, the TC rain rate has increased by 8 ± 4% during this period, which is mainly contributed by an increase in rain rate in the TC outer region due to increasing water vapor availability in the atmosphere with rising surface temperature. On the other hand, the rain rate in the inner-core of TCs has decreased by 24 ± 3% during the same period. The decreasing trend in the inner-core rain rate likely results mainly from an increase in atmospheric stability. How the rainfall intensity of tropical cyclones changes with climate change is not well known. Here, the authors show that while the rain rate in the outer region of TCs is clearly increasing between 1999 and 2018, it decreases significantly in the inner-core of TCs during 1999-2018.

This study examines the long-term change in the threat of landfalling tropical cyclones (TCs) in East Asia over the period 1975–2020 with a focus on rapidly intensifying (RI) TCs. The increase in the annual number of RI-TCs over the western North Pacific and the northwestward shift of their genesis location lead to an increasing trend in the annual number of landfalling RI-TCs along the coast of East Asia. The annual power dissipation index (PDI), a measure of the destructive potential of RI-TCs at landfall, also shows a significant increasing trend due to increases in the annual frequency and mean landfall intensity of landfalling RI-TCs. The increase in mean landfall intensity is related to a higher lifetime maximum intensity (LMI) and the LMI location of the landfalling RI-TCs being closer to the coast. The increase in the annual PDI of East Asia is mainly associated with landfalling TCs in the southern (the Philippines, South China, and Vietnam) and northern parts (Japan and the Korean Peninsula) of East Asia due to long-term changes in vertical wind shear and TC heat potential. The former leads to a northwestward shift of favorable environments for TC genesis and intensification, resulting in the northwestward shift in the genesis, RI, and LMI locations of RI-TCs. The latter provides more heat energy from the ocean for TC intensification, increasing its chances to undergo RI.

The increase in intense tropical cyclone (TC) activity across the western North Pacific (WNP) has often been attributed to a warming ocean. However, it is essential to recognize that the tropical WNP region already boasts high temperatures, and a marginal increase in oceanic warmth due to global warming does not exert a significant impact on the potential for TCs to intensify. Here we report that the weakened vertical wind shear is the primary driver behind the escalating trend in TC intensity within the summer monsoon trough of the tropical WNP, while local ocean surface and subsurface thermodynamic factors play a minor role. Through observational diagnoses and numerical simulations, we establish that this weakening of the vertical wind shear is very likely due to the increase in temperature of the Tibetan Plateau. With further warming of the Tibetan Plateau under the Representative Concentration Pathway 4.5 scenario, the projected TCs will likely become stronger. The weakened vertical wind shear is the primary driver behind increasing tropical cyclone intensity in the western North Pacific monsoon trough. This weakening is partly driven by warming in the Tibetan Plateau.

Most studies on tropical cyclone (TC) rain rate focus on long-term variability, yet the short-term (days or shorter) variations across the TC lifecycle, with a particular focus on the period before landfall, are most critical because they strongly influence flood risk. Using satellite data, we show that, globally, the mean rain rate of TCs increases by over 20% from 60 hours before landfall to the time of landfall. This increase occurs across hemispheres, ocean basins, intensity categories, and latitudes, although the magnitude varies. As a TC approaches the coast, land-sea thermal contrasts raise low-level humidity over land, while frictional differences enhance convergence, upward motion, and instability on the offshore side of the circulation. These conditions collectively promote increased convection and precipitation of TCs as they near landfall. Our findings critically strengthen the current understanding of TC precipitation dynamics and support more effective flood management. Tropical cyclone rain rates rise by over 20% in the 60 hours before landfall, which is driven by land–sea thermal and friction contrasts, heightening coastal flood risk. In addition, this enhancement has implications for forecasting and preparedness.

Hailstorms rank among the most destructive extreme weather events globally, causing substantial property damage. While limited case studies suggest that cities may exacerbate hailstorms, the underlying mechanisms remain uncertain because of the complex physical processes. Here, we examine a hailstorm formation pathway associated with convective merging process using long-term observational data and high-resolution numerical simulations. This pathway helps explain the rising frequency of hailstorms across two distinct climate regimes, North America and East Asia. We find that merger hailstorms (MHs) occur approximately twice as often and tend to be more intense than non-merging normal hailstorms (NHs), which have been traditionally considered as the primary hailstorm formation mode. Favorable environmental conditions support the initiation of multiple convective cells and their subsequent merging, a tendency that may be enhanced by anthropogenic heat in large cities. Projections from a machine-learning model indicate an increase in the MH frequency and a decrease in NH frequency in North America. Together, these findings highlight an underexplored hailstorm formation pathway and suggest that climate change and human activities may play a role in shaping future hailstorm characteristics and the associated risks. This study reveals a merger-type hailstorm formation pathway that is twice as frequent and more intense than traditional hailstorms and is projected to increase in North American cities, potentially amplified by anthropogenic influence.

With an average of 26 tropical cyclones (TCs) per year, the western North Pacific (WNP) is the most active TC basin in the world. Considerable exposure lies in the coastal regions of the WNP, which extends from Japan in the north to the Philippines in the south, amplifying TC related impacts, including loss of life and damage to property, infrastructure and environment. This study presents a new location-specific typhoon (TY) and super typhoon (STY) outlook for the WNP basin and subregions, including China, Hong Kong, Japan, Korea, Philippines, Thailand, and Vietnam. Using multivariate Poisson regression and considering up to five modes of ocean-atmospheric variability and teleconnection patterns that influence WNP TC behaviour, thousands of possible predictor model combinations are compared using an automated variable selection procedure. For each location, skillful TY and STY outlooks are generated up to 6 months before the start of the typhoon season, with rolling monthly updates enabling refinement of predicted TY and STY frequency. This unparalleled lead time allows end-users to make more informed decisions before and during the typhoon season.