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<p>Tropical Cyclones Translation Speed (TCTS), which represents the rate at which tropical cyclones move across a region, plays a critical role in determining the extent of TC-induced destructiveness. However, variations in TCTS and associated mechanisms remain unexplored for TCs activity over the Bay of Bengal (BoB). This study examines the variability of TCTS over BoB during a 43-year period (1982–2024). Analysis is conducted by objectively dividing the study period into two distinct epochs: the Past Epoch (PE; 1982–2002) and Recent Epoch (RE; 2003–2024). Results reveal a notable decline in mean TCTS of approximately 10.3% (1.55&#xa0;km h⁻¹) during post-monsoon season in RE (13.59&#xa0;km h⁻¹) compared to the seasonal mean TCTS (15.14&#xa0;km h⁻¹), with overall mean reducing from 16.62&#xa0;km h⁻¹ during PE to 13.59&#xa0;km h⁻¹ in RE. Results based on best-tracks data suggest that the decline in TCTS during RE is mainly due to a shift in latitudinal distribution of TCs activity. During PE, TCs exhibited a slight poleward displacement with faster translation speeds, while in the RE, TCs are predominantly confined to lower latitudes, moving westward or north-westward with reduced TCTS. Further, the diagnosis of atmospheric steering flows along with Wave Activity Flux and meridional Mass Streamfunction analyses unveil that concurrent changes in the activity of mid-latitude Rossby wave and tropical Hadley cell circulation plays a vital role in causing an epochal shift of the observed TCs track activity and their TCTS via modulating prevailing steering flow patterns and their background strengths (wind speeds). The findings highlight a key shift in TCTS behaviour over the BoB region and underscore the importance of understanding tropical (e.g. Hadley cell) and sub-tropical (e.g. mid-latitude Rossby wave) dynamics while forecasting TCs motion.</p>

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Mechanism on the epochal shift in translation speed of tropical cyclones formed over the Bay of Bengal region

  • 期刊论文

  • 发表日期：

    2026年3月17日

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  • Mohan Murali Krishna Gorja,
  • Naresh Krishna Vissa,
  • Yesubabu Viswanadhapalli,
  • Gopinadh Konda,
  • Venkata Sai Gulakaram

摘要

Tropical Cyclones Translation Speed (TCTS), which represents the rate at which tropical cyclones move across a region, plays a critical role in determining the extent of TC-induced destructiveness. However, variations in TCTS and associated mechanisms remain unexplored for TCs activity over the Bay of Bengal (BoB). This study examines the variability of TCTS over BoB during a 43-year period (1982–2024). Analysis is conducted by objectively dividing the study period into two distinct epochs: the Past Epoch (PE; 1982–2002) and Recent Epoch (RE; 2003–2024). Results reveal a notable decline in mean TCTS of approximately 10.3% (1.55 km h⁻¹) during post-monsoon season in RE (13.59 km h⁻¹) compared to the seasonal mean TCTS (15.14 km h⁻¹), with overall mean reducing from 16.62 km h⁻¹ during PE to 13.59 km h⁻¹ in RE. Results based on best-tracks data suggest that the decline in TCTS during RE is mainly due to a shift in latitudinal distribution of TCs activity. During PE, TCs exhibited a slight poleward displacement with faster translation speeds, while in the RE, TCs are predominantly confined to lower latitudes, moving westward or north-westward with reduced TCTS. Further, the diagnosis of atmospheric steering flows along with Wave Activity Flux and meridional Mass Streamfunction analyses unveil that concurrent changes in the activity of mid-latitude Rossby wave and tropical Hadley cell circulation plays a vital role in causing an epochal shift of the observed TCs track activity and their TCTS via modulating prevailing steering flow patterns and their background strengths (wind speeds). The findings highlight a key shift in TCTS behaviour over the BoB region and underscore the importance of understanding tropical (e.g. Hadley cell) and sub-tropical (e.g. mid-latitude Rossby wave) dynamics while forecasting TCs motion.