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During the recent decades of satellite era, more tropical cyclogenesis locations (TCLs) were observed over the northwestern part of the western North Pacific (WNP), relative to the southeastern part, during the boreal autumn. This increase in TCLs over the northwestern WNP is largely attributed to the synergy of shifting El Niño-Southern Oscillation (ENSO) and the 1998 Pacific climate regime shift. Both central Pacific (CP) La Niña and CP El Niño have occurred more frequently since 1998, with only one eastern Pacific El Niño observed in autumn 2015. The change in the mean longitude of TCLs is closely linked to the ENSO diversity, whereas the change in the mean latitude is dominated by the warming of the WNP induced by an interdecadal tendency of CP La Niña-like events. The physical mechanisms responsible for this shifting ENSO-TCL linkage can be potentially explained by the tacit-and-mutual configurations between tropical upper-tropospheric trough and monsoon trough, on both interannual and interdecadal timescales, which is mainly due to the ENSO-related large-scale environment changes in ocean and atmosphere that modulate the WNP TCL.

Tropical cloud clusters (TCCs) can potentially develop into tropical cyclones (TCs), leading to significant casualties and economic losses. Accurate prediction of tropical cyclogenesis (TCG) is crucial for early warnings. Most traditional deep learning methods applied to TCG prediction rely on predictors from a single time point, neglect the ocean-atmosphere interactions, and exhibit low model interpretability. This study proposes the Tropical Cyclogenesis Prediction-Net (TCGP-Net) based on the Swin Transformer, which leverages convolutional operations and attention mechanisms to encode spatiotemporal features and capture the temporal evolution of predictors. This model incorporates the coupled ocean-atmosphere interactions, including multiple variables such as sea surface temperature. Additionally, causal inference and integrated gradients are employed to validate the effectiveness of the predictors and provide an interpretability analysis of the model’s decision-making process. The model is trained using GridSat satellite data and ERA5 reanalysis datasets. Experimental results demonstrate that TCGP-Net achieves high accuracy and stability, with a detection rate of 97.9% and a false alarm rate of 2.2% for predicting TCG 24 hours in advance, significantly outperforming existing models. This indicates that TCGP-Net is a reliable tool for tropical cyclogenesis prediction.

Understanding the role of tropical cloud clusters (TCC) in the development of tropical cyclones involves various complexities and, thus, necessitates precise research. The study on TC development from the TCCs is still minimal. The present research is carried out to investigate the predictability of Tropical cyclogenesis (TCG) by examining the Rossby Radius Ratio (RRR) and Daily Genesis Potential (DGP) of different cloud clusters over the four ocean basins in the Northern Hemisphere, viz., North Indian Ocean (NIO), North Atlantic Ocean (NAO), West Pacific Ocean (WPO), and East Pacific Ocean (EPO). The analysis of the TCC data, taken for the period 1996–2005, shows that both the predictors are skilled at identifying the developed and non-developed TCCs. The method of cumulative distribution is implemented to identify the threshold ranges of RRR and DGP. In addition, the forecast skill scores are estimated for the selected predictors. The rough set theory based on different condition-decision support is implemented to estimate the certainty in the TCG prediction scheme with each predictor individually and in combination. The result shows that higher certainty in TCG prediction is observed when RRR ≤ 24 and DGP ≥ 1.21 × 10−5 for the NIO basin. However, it is to be noted that the combination of both RRR and DGP provides better confidence in the predictability of TCG over the NAO basin (RRR ≤ 38 and DGP ≥ 0.71 × 10−5) and EPO basin (RRR ≤ 28.7 and DGP ≥ 0.47 × 10−5). Furthermore, RRR (threshold value ≤ 28.2) individually gives better predictability for TCG over the WPO basin. The forecasts of TCG with RRR and DGP are validated with the observations from 2006 to 2009.

Previous studies have focused mostly on the impact of lower‐level vorticity growth and other lower‐level processes on tropical cyclogenesis (TCG). In this study, the importance of upper‐level processes in TCG is studied in terms of the minimum sea‐level pressure (MSLP) changes with two cases exhibiting different warm‐core heights and vorticity structures due to their developments in the respective weak‐ and strong‐sheared environment. Results show that the upper‐level warming could account for more than 75% the MSLP changes in both cases. Widespread deep convection during the early TCG stage tends to warm the upper troposphere and induce meso‐α‐scale surface pressure falls. Upper‐level flow and vertical wind shear (VWS) will suppress the formation of a warm core due to the presence of weak inertial stability, whereas the development of upper‐level divergent outflows favors its formation. Results also show that TCG is triggered when the upper‐level warming amplitude and depth increase as a result of weak or significantly reduced ventilation and VWS aloft. Results suggest that both the upper‐ and low‐level processes be considered in the understanding and prediction of TCG. Key Points Tropical cyclogenesis is triggered as the upper‐level warming increases Upper‐level flow and shear are detrimental to tropical cyclogenesis The upper‐ and low‐level processes play different roles in tropical cyclogenesis

It has been proposed that tropical cyclogenesis rates can be expressed as the product of the frequency of “seeds” and a transition probability that depends on the large-scale environment. Here it is demonstrated that the partitioning between seed frequency and transition probability depends on the seed definition and that the existence of such a partition does not resolve the long-standing issue of whether tropical cyclone frequency is controlled more by environmental conditions or by the statistics of background weather. It is here argued that tropical cyclone climatology is mostly controlled by regional environment and that the response of global tropical cyclone activity to globally uniform radiative forcing may be more controlled by the regionality of the response than by the mean response.

An African easterly wave (AEW) and associated mesoscale convective systems (MCSs) dataset has been created and used to evaluate the propagation of MCSs, AEWs, and, especially, the propagation of MCSs relative to the AEW with which they are associated (i.e., wave-relative framework). The thermodynamic characteristics of AEW–MCS systems are also analyzed. The analysis is done for both AEW–MCS systems that develop into tropical cyclones and those that do not to quantify significant differences. It is shown that developing AEWs over West Africa are associated with a larger number of convective cloud clusters (CCCs; squall-line-type systems) than nondeveloping AEWs. The MCSs of developing AEWs propagate at the same speed of the AEW trough in addition to being in phase with the trough, whereas convection associated with nondeveloping AEWs over West Africa moves faster than the trough and is positioned south of it. These differences become important for the intensification of the AEW vortex as this slower-moving convection (i.e., moving at the same speed of the AEW trough) spends more time supplying moisture and latent heat to the AEW vortex, supporting its further intensification. An analysis of the rainfall rate (MCS intensity), MCS area, and latent heating rate contribution reveals that there are statistically significant differences between developing AEWs and nondeveloping AEWs, especially over West Africa where the fraction of extremely large MCS areas associated with developing AEWs is larger than for nondeveloping AEWs.

This study investigates the seasonal cycle of tropical cyclones (TCs) in the North Indian Ocean (NIO) using a multi‐stage framework of tropical cyclogenesis that considers the TC seeds and TCs separately. We find that the May–June (MJ) pre‐monsoon season features fewer TC seeds (∼23) with high survival rates (SR, ∼2.8%), while the post‐monsoon season October‐November (ON) shows abundant TC seeds (∼66) with low SR (∼1.8%). Genesis potential indices (GPIs), which combine key environmental factors, capture the TC seed numbers and spatial distribution but fail to explain SR differences between seasons. Composite analysis reveals that MJ season TC seeds exhibit more intense convection, suggesting additional sources of instability not included in current GPIs, potentially related to horizontal gradient of moisture. These findings highlight the importance of considering both TC seed numbers and SR when investigating TC frequency in the NIO and show GPIs' limitations that focus solely on local environmental variables.

Idealized simulations of tropical moist convection have revealed that clouds can spontaneously clump together in a process called self-aggregation. This results in a state where a moist cloudy region with intense deep convection is surrounded by extremely dry subsiding air devoid of deep convection. Because of the idealized settings of the simulations where it was discovered, the relevance of self-aggregation to the real world is still debated. Here, we show that self-aggregation feedbacks play a leading-order role in the spontaneous genesis of tropical cyclones in cloud-resolving simulations. Those feedbacks accelerate the cyclogenesis process by a factor of 2, and the feedbacks contributing to the cyclone formation show qualitative and quantitative agreement with the self-aggregation process. Once the cyclone is formed, wind-induced surface heat exchange (WISHE) effects dominate, although we find that self-aggregation feedbacks have a small but nonnegligible contribution to the maintenance of the mature cyclone. Our results suggest that self-aggregation, and the framework developed for its study, can help shed more light into the physical processes leading to cyclogenesis and cyclone intensification. In particular, our results point out the importance of the longwave radiative cooling outside the cyclone.

Future climate projections suggest a poleward shift of the maximum intensity of tropical cyclones (TCs) over the western North Pacific. However, the global nature of the latitudinal change in TC genesis under global warming remains poorly understood. We show, using large‐ensemble high‐resolution atmospheric model simulations (d4PDF) with four warming scenarios, that the poleward shift is a robust change over the globe, attributable to the weakening of the Hadley circulation. The weakened ascent driven by the upper‐tropospheric warming suppresses the TC genesis within 5°–20° latitudes, whereas the weakened descent enhances the TC genesis in the poleward latitudes. We further estimate the poleward shift of TC genesis to emerge at the 2 K global warming over the Arabian Sea, South Atlantic and Pacific Oceans and at the 4 K warming over the North Pacific. The present results underscore the potential for increasing social and economic risks associated with TCs at higher latitudes. Plain Language Summary Climate models have projected a decrease in TC genesis frequency in future warming. However, the global nature of the latitudinal change in TC genesis under global warming remains uncertain partly due to insufficient resolution as well as the ensemble size of climate model simulations. We show a global feature of the robust poleward shift of the TC genesis during the active seasons of both hemispheres scaled with the global warming level, which can be attributed to the weakening of the Hadley circulation. The weakened ascending branch of the Hadley circulation, driven by the increased upper tropospheric warming, potentially hinders TC genesis within 5°–20° latitudes. Conversely, the weakened descending branch of the Hadley circulation enhances the likelihood of TC genesis within 20°–35° latitudes. We further estimate that the signal of TC genesis is expected to emerge over high latitudes of the Arabian Sea, South Atlantic and South Pacific Oceans at the 2 K warming and at the 4 K warming over the North Pacific. The present analyses have significant implications not only for assessing the reliability of future TC‐related changes in climate models but also for estimating the increased TC‐related hazards at higher latitudes under global warming. Key Points We project a global feature of the robust poleward shift of tropical cyclone (TC) genesis during active seasons of both hemispheres More TC genesis at high latitudes can be attributed to the weakening of the Hadley circulation Poleward shift of TC genesis emerges at 2 K warming over Arabian Sea, South Atlantic and Pacific Oceans and at 4 K warming over North Pacific

Eastern Africa is a common region of African easterly wave (AEW) onset and AEW early life. How the large-scale environment over East Africa relates to the likelihood of an AEW subsequently undergoing tropical cyclogenesis in a climatology has not been documented. This study addresses the following hypothesis: AEWs that undergo tropical cyclogenesis (i.e., developing AEWs) initiate and propagate under a more favorable monsoon large-scale environment over eastern Africa when compared with nondeveloping AEWs. Using a 21-yr August–September (1990–2010) climatology of AEWs, differences in the large-scale environment between developers and nondevelopers are identified and are proposed to be used as key predictors of subsequent tropical cyclone (TC) formation and could inform tropical cyclogenesis prediction. TC precursors when compared with nondeveloping AEWs experience an anomalously active West African monsoon, stronger northerly flow, more intense zonal Somali jet, anomalous convergence over the Marrah Mountains (region of AEW forcing), and a more intense and elongated African easterly jet. These large-scale conditions are linked to near-trough attributes of developing AEWs that favor more moisture ingestion, vertically aligned circulation, a stronger initial 850-hPa vortex, a deeper wave pouch, and arguably more AEW and mesoscale convective systems interactions. AEWs that initiate over eastern Africa and cross the west coast of Africa are more likely to undergo tropical cyclogenesis than those initiating over central or West Africa. Developing AEWs are more likely than nondeveloping AEWs to be southern-track AEWs.