  Arabian Sea Mid-Tropospheric Cyclones (MTCs), which are responsible for
extreme rainfall events in western India, often coincide with monsoon
low-pressure systems (LPS) over the Bay of Bengal. However, the role of Bay of
Bengal LPSs in the formation of Arabian Sea MTCs remains unclear. This study
utilizes the Weather Research and Forecasting Model (WRF) to investigate the
atmospheric connection between the two basins. By introducing a balanced bogus
vortex over the Bay of Bengal, cyclonic systems are induced over the Arabian
Sea in the majority of ensemble members, exhibiting characteristics consistent
with observations. As the Bay of Bengal vortex moves westward, the middle
tropospheric trough deepens, horizontal wind shear increases, the low-level
Arabian Sea stable inversion layer weakens, and the middle troposphere moisture
content increases over western India and the northeast Arabian Sea.
Subsequently, MTC genesis occurs along the western edge of the trough within
2-4 days of model integration over the northeast Arabian Sea. Vorticity budget
analysis highlights the critical role of vorticity advection and tilting during
the initial 24 hours of MTC genesis, while vortex stretching becomes the
dominant vorticity source during rapid intensification. To further substantiate
these findings, a mechanism denial experiment is conducted using a real-world
instance of coexistent Arabian Sea MTC and Bay of Bengal LPS, which was
replicated in the model. In the experiment, conditions unfavorable for LPS
genesis are created by cooling and drying the Bay of Bengal. The results
demonstrate that when the Bay of Bengal LPS does not develop or intensify, the
Arabian Sea MTC fails to form. This study presents compelling evidence for the
significant influence of Bay of Bengal low-pressure systems on the formation of
severe weather-inducing MTCs over the Arabian Sea and western India.
