Search

Observations and climate projections suggest a larger increase in tropical cyclone (TC)‐induced rainfall than that can be explained by the Clausius‐Clapeyron relationship of 7% increase in vapor content for each 1°C degree rise in temperature. However, these studies using diverse data sources and methods over various periods show inconsistencies regarding the location of this increase ‐ whether in the TC inner core or outer regions ‐ and offer differing explanations for the reported trends. This study uses the Pseudo‐global warming methodology on simulations of 117 western North Pacific TCs making landfall in Southeast Asia to investigate changes in TC rainfall structure by the end of the century under the SSP2‐4.5 and SSP3‐7.0 scenarios. Specifically, it tests the sensitivity of changing trends to various analysis methods used in previous studies and identifies the underlying physical mechanisms driving these changes. The findings indicate an amplified increase in rainfall in the TC inner core across all future scenarios, along with potentially decreased rainfall in the outer region under certain future climate conditions. Among TC categories, Supertyphoons exhibit the most significant increased rainfall across future states. Changes in TC primary and secondary circulations, TC structure, and the convergence of heat and moisture are the main factors shaping future rainfall patterns, outweighing the effects of changes in atmospheric and convective stability. Plain Language Summary: Tropical cyclone (TC)‐related rainfall is increasing with global warming. Typically, a 1°C increase in temperature leads to about a 7% increase in the atmosphere's water vapor holding capacity. However, the rise in TC rainfall outpaces this rate. Observations indicate this enhanced increase occurs in the TC outer region due to greater environmental moisture. Contrarily, modeling future projections suggest this concentrates in the inner core due to intensified TCs. This study analyzes a large data set of 819 simulations from 117 TCs making landfall in Southeast Asia to capture changes in future rainfall patterns under two contemporary climate change scenarios. Our findings reveal that the enhanced increase occurs in the TC inner core in all future states, while rainfall in the outer region decreases under specific climate conditions. Supertyphoons generate the heaviest rainfall, with minimal variations observed across climate scenarios. Variations of all dynamic and thermodynamic factors closely tied to TC rainfall are investigated to provide a comprehensive picture of the physics behind the changes. The interplay between TC dynamics (e.g., primary and secondary circulations), TC structure, and thermodynamic conditions (e.g., convergence of moisture, and temperatures), plays a critical role in the changing behaviors of TC rainfall. Key Points: Rainfall increases in the cyclone's inner core across all future states but decreases in the outer region under specific statesVariations in cyclone circulations, structure, convergence of moisture and heat in future climates drive rainfall changing patternsSupertyphoons cause the heaviest rainfall compared to other categories, with slight variations noted across climate conditions [ABSTRACT FROM AUTHOR]

In this Pseudo‐global Warming study, potential future changes in the Southeast Asia tropical cyclone (TC) exposure climatology are quantified. One hundred and seventeen landfalling TCs in the last 20 years are simulated with their current climate conditions and also with the Coupled Model Intercomparison Project Phase 6 (CMIP6) ensemble perturbed conditions under the SSP2‐4.5 and SSP3‐7.0 climate change scenarios. Our simulations suggest that landfalling TCs are projected to be 8% more intense at landfall, 2.8% faster and have smaller sizes by the end of the 21st century under the SSP3‐7.0 scenario. In addition, TC landfall locations shift northward with tracks extending further inland toward Laos and Thailand. In particular, TC exposures, wind and rainfall impacts significantly increase in the northern Philippines, Taiwan, southwestern coast of China, and northern Vietnam; and significantly decrease in the southern areas of Southeast Asia and the southeastern coast of China. Key Points: Tropical cyclones are projected to be more intense, smaller in size, and to move fasterLandfalling locations shift poleward and further west by the end of the 21st centuryWind and rain impacts increase in the northern Southeast Asia, extend further inland [ABSTRACT FROM AUTHOR]

The North Indian Ocean is a region with a high coastal population and a low-lying delta, making it a high-risk region for tropical cyclone impacts. A 30-year period from 1989–2018 has been used to examine the TC landfalling exposure in the North Indian Ocean and its changes by considering 30 years of IBTrACs data, ERA5 atmospheric data, and 20 years of TRMM and DAV data. A total of 185 TCs made landfall in the NIO during the 30-year period with the majority of the TCs making landfall during the pre- and post-monsoon seasons. Rainfall associated with landfalling TCs decreased in the last 10 years of analysis (2009–2018) compared to the first 10 years of available data from 1999–2008. During the monsoon, TC activity is relatively lower compared to the post-monsoon periods, even though higher accumulated TC-associated rainfall typically occurs during the monsoon period, particularly along the eastern coastlines of the Arabian Sea and the Bay of Bengal. The TC winds impact most of the Bay of Bengal coastline, including Sri Lanka. The spatial distribution of landfalling TCs changes with the season, with most of the landfalling activity occurring during the pre- and post-monsoon periods. Interestingly, more recent TC activity has shifted to the northeast India and Bangladesh coasts, suggesting that these regions may be more vulnerable to TC impacts in the future. [ABSTRACT FROM AUTHOR]

In this study, the landfalling tropical cyclone (TC) exposure in Southeast Asia for a 50‐year period from 1970 to 2019 is investigated relative to the total western North Pacific (WNP) climatology taking disparities in historical records into account. Long‐term trends in landfalling TCs are analyzed and intercompared among the Regional Specialized Meteorological Center of Tokyo (TOKYO), China Meteorological Administration (CMA), Hong Kong Observatory (HKO), and Joint Typhoon Warning Center (JTWC) best track datasets. Interannual and intra‐seasonal variations are further examined by sub‐region and nation using JTWC records. Approximately half of the WNP TCs make landfall in Southeast Asia representing over 75% of the total WNP landfalls in all datasets. Over the study period, there is a slight upward trend in landfalling TC frequency in both the WNP and Southeast Asia in the JTWC dataset, while the number of landfall events has decreased in the CMA and TOKYO datasets. A consistent northward shift in landfalling locations over the 50‐year period is found in all datasets such that landfalls have decreased in the Philippines, Vietnam, but increased in some South China areas. The TOKYO dataset alone suggests that landfalling TCs in South China have slowed down over the study period, which would increase rainfall and wind risks in their path if substantiated. Less TC landfalls occur in El Niño years with landfalling locations shifting northwestward over the Asian mainland, while landfalls are higher and more distributed in La Niña, and highest in Neutral years. Key Points: Approximately half of all Western North Pacific tropical cyclones made landfall in Southeast AsiaA northward shift of landfalling locations is found in all four agency best track recordsLandfalls are lower and shifted northwestward in El Niño, higher and more distributed in La Niña, and highest in Neutral years [ABSTRACT FROM AUTHOR]

Tropical Cyclone Oswald (2013) is considered to be one of the highest-impact storms to make landfall in northern Australia even though it only reached a maximum category 1 intensity on the Australian category scale. After making landfall on the west coast of Cape York Peninsula, Oswald turned southward, and persisted for more than 7 days moving parallel to the coastline as far south as 308S. As one of the wettest tropical cyclones (TCs) in Australian history, the favorable configurations of a lower-latitude active monsoon trough and two consecutive midlatitude trough–jet systems generally contributed to the maintenance of the Oswald circulation over land and prolonged rainfall. As a result, Oswald produced widespread heavy rainfall along the east coast with three maximum centers near Weipa, Townsville, and Rockhampton, respectively. Using high-resolution WRF simulations, the mechanisms associated with TC Oswald’s rainfall are analyzed. The results show that the rainfall involved different rainfall mechanisms at each stage. The land–sea surface friction contrast, the vertical wind shear, and monsoon trough were mostly responsible for the intensity and location for the first heavy rainfall center on the Cape York Peninsula. The second torrential rainfall near Townsville was primarily a result of the local topography and land–sea frictional convergence in a conditionally unstable monsoonal environment with frictional convergence due to TC motion modulating some offshore rainfall. The third rainfall area was largely dominated by persistent high vertical wind shear forcing, favorable large-scale quasigeostrophic dynamic lifting from two midlatitude trough–jet systems, and mesoscale frontogenesis lifting. [ABSTRACT FROM AUTHOR]

A dataset of 167 eastern North Pacific tropical cyclones (TCs) is investigated for potential impacts in the southwestern United States over the period 1989-2009 and evaluated in the context of a 30-yr climatology. The statistically significant patterns from empirical orthogonal function (EOF) analysis demonstrate the prevalence of a midlatitude trough pattern when TC-related rainfall occurs in the southwestern United States. Conversely, the presence of a strong subtropical ridge tends to prevent such events from occurring and limits TC-related rainfall to Mexico. These statistically significant patterns correspond well with previous work. The El Niño-Southern Oscillation phenomenon is shown to have some effect on eastern North Pacific TC impacts on the southwestern United States, as shifts in the general circulation can subsequently influence which regions receive rainfall from TCs or their remnants. The Pacific decadal oscillation may have a greater influence during the period of study as evidenced by EOF analysis of sea surface temperature anomalies. [ABSTRACT FROM AUTHOR]

Forty-three eastern North Pacific tropical cyclone remnants with varying impact on the southwestern United States during the period 1992--2005 are investigated. Of these, 35 remnants (81%%) brought precipitation to some part of the southwestern United States and the remaining 8 remnants (19%%) had precipitation that was almost entirely restricted to Mexico, although cloud cover did advect over the southwestern United States in some of these cases. Although the tropical cyclone--strength winds rapidly diminish upon making landfall, these systems still carry a large quantity of tropical moisture and, upon interaction with mountainous topography, are found to drop up to 30%% of the local annual precipitation. Based on common rainfall patterns and large-scale circulation features, the tropical cyclones are grouped into five categories. These include a northern recurving pattern that is more likely to bring rainfall to the southwestern United States; a southern recurving pattern that brings rainfall across northern Mexico and the Gulf Coast region; a largely north and/or northwestward movement pattern that brings rainfall to the west coast of the United States; a group that is blocked from the southwest by a ridge, which limits rainfall to Mexico; and a small group of cases that are not clearly any of the previous four types. Composites of the first four groups are shown and forecasting strategies for each are described. [ABSTRACT FROM AUTHOR]

The extratropical cyclone development processes during the reintensification stage of an extratropical transition from a tropical cyclone (TC) are described using numerical simulations. Three control simulations without a tropical cyclone present examine the extratropical cyclogenesis associated with upper-level troughs that are characterized as weak, moderate, and strong. When no tropical cyclone is included in the simulation, the minimum surface pressures attained with the weak, moderate, and strong troughs are 1003, 991, and 977 mb, respectively. In all three cases, the low tilts northwestward with height during intensification, and the rainfall pattern and eventual occlusion are representative of classic extratropical cyclone development. The interactions of a tropical cyclone with each of the three midlatitude circulation patterns are compared with the control simulations to illustrate the contributions to the extratropical transition of the tropical cyclone. In the three trough-with-TC cases, the minimum surface pressures were almost identical (967, 965, and 959 mb). Thus, the final intensity of the extratropical cyclone is not only related to the strength of the upper-level trough but must also be related to the structure of the basic midlatitude environment. The proper phasing of the tropical cyclone with the midlatitude trough results in substantial enhancement of the upper-level divergence. In addition, higher θ[sub e] values in the lower troposphere associated with the tropical cyclone remnants are absorbed in the developing extratropical cyclone. The lifting of this moist air results in precipitation that is greater in both amount and areal extent, which enhances extratropical development when compared with the control cases. Based on these simulations, an important conclusion is that a weak midlatitude trough interacting with tropical cyclone remnants may have as much potential to intensify, as does a moderate or strong trough, and may have longer periods of rapid intensification. A development potential parameter based on the three main factors in the Petterssen development equation (upper-level divergence, midlevel positive vorticity advection, and low-level temperature advection) is calculated for all simulations. The strength and areal extent of the development parameter has utility in predicting where and whether extratropical cyclogenesis will occur during the reintensification stage of extratropical transition. [ABSTRACT FROM AUTHOR]