## 3 Results
### Cyclogenesis Parameters Such as RH, VWS, Vorticity, and PI  
Schemes in the time of global warming show that the pumping of moisture into a rain-bearing system can eventually enhance the system to extremes. The mean tropospheric moisture (MTM) in the troposphere is vital for TC formation (Figure 5). The MTM anomalies (%) in the mid-troposphere, depicted in Figure 5, clearly show a steady increase in moisture content during 2012-2021, particularly over the AS compared to previous decades. High MTM supports sustained convection and enhances the likelihood of TC development. This rise in RH is directly linked to the observed increase in TCs during the last decade. Another important variable is the VWS; a magnitude below 12 m/s can intensify the TCs over the BoB, as discussed by [PERSON] et al. [37]. The VWS anomalies, defined as the wind vector difference between the 200 and 850 hPa levels, commonly referred to as \"deep-layer\". The VWS, rank as the second most important predictor of TC intensity, as discussed by [PERSON] et al. [38]. Figure 4: Horizontal distribution of the mean sea-level pressure (MSLP; hPa) anomaly in three decades (**a**) 1992–2001, (**c**) 2002–2011, and (**e**) 2012–2021 during the OND season. Figure (**b,d,f**) are the same as (**a,c,e**), but for the stream flow pattern and wind isotachs (shaded; ms\({}^{-1}\)) at an 850 hPa level derived from ERA5 reanalysis at a 25 km resolution. Figure 5: Spatial distribution of mean tropospheric moisture (MTM) in three decades, (**a**) 1992–2001, (**b**) 2002–2011, and (**c**) 2012–2021, derived from ERA5 reanalysis at a 25 km resolution. The VWS anomalies during each decade indicate that VWS weakened and became confined to a narrow corridor during 2012-2021 (Figure 6c). The lowest VWS in the magnitude of \(-2.1\) m/s is shown over the AS, as represented in Figure 6c, which is a critical parameter for TC intensification, allowing storms to maintain their vertical structure. This reduction in shear helps explain the rapid intensification of TCs before landfall in recent years. On the other hand, VWS (which opposes TC development when strong) has decreased, further aiding TC formation and intensification, particularly in the BoB. In two decades, 2002-2011 and 2012-2021, dipole-type structures of positive and negative anomalies in the western equatorial IO and central India stretched towards the AS, as shown in Figure 6b,c. The intensity of a low-pressure system is defined in terms of positive vorticity. Positive vorticity anomalies at 850 hPa levels, which indicate cyclonic rotation, are higher over the Indian Ocean (Figure 7a-c). The vorticity at lower level have shifted over the northern part of the AS and BoB from earlier decades to 2012-2021. Overall, Figure 4 suggests more favorable conditions for TC genesis. The intrusion of vorticity from the AS to the Indian landmass has been interesting to watch in recent decades. The year-to-year relative vorticity at 850 hPa variability shows a linear increase in VWS over the AS (Figure 8c). The Arabian Sea exhibits increasing vorticity and decreasing wind shear, along with heightened instability, particularly in the last decade depicted in Figure 8a,b. The westward shift of warming from the South China Sea is clearly evident in recent decades, as shown in Figure 8c. Figure 9 shows the interannual variations and trends of the fundamental variables required for the formation and sustenance of tropical cyclones over the Arabian Sea. In general, the wind shear and moisture are quite high during the summer monsoon, which decreases substantially after the post-monsoon (OND) season. The increase in moisture and VWS contributed to the formation of cyclones over the AS, as shown in Figure 9a,b. The increase in wind shear is one of the main reasons for the formation of a number of cyclones over the AS in recent years (2012-2021). Wind, along with another parameter of moisture (MRH anomalies; Figure 5c), shows a cyclonic pattern extended from Gujarat towards AS at 850 hPa in Figure 4f.