Representational image of a cyclone


Earlier this month, a tropical depression that formed in the Bay of Bengal on May 6 intensified into a cyclonic storm on May 7, effectively becoming the first cyclone of the year in the north Indian Ocean. Named Cyclone Asani, this system attained a maximum wind speed of 65 knots (category 1) on May 10, as per observations by the Joint Typhoon Warning Center (JTWC).

Despite attaining such power, however, the cyclone was unable to maintain its intensity, and it eventually made landfall on the Andhra Pradesh coast as a weakened deep depression. But how and why did this happen? Let’s analyse.

An unusual pre-monsoon cyclone

Cyclones that form in the Bay of Bengal during the pre-monsoon season (April-June) generally head in a north-northeastward direction, and make landfall at the coasts of India’s West Bengal, Bangladesh or Myanmar.

Cyclone Asani, however, moved in a west-northwest direction and hit the Andhra Pradesh coast as a tropical depression.

Based on the India Meteorological Department (IMD) records, it was only the fourth cyclone to hit the Andhra Pradesh coast during the pre-monsoon season (April-June) in the satellite period (1980-2022).

Barriers in intensification

Despite very favourable conditions such as high sea surface temperatures in the range of 31-32°C and tropical cyclone heat potential in the range of 100-120 kJ cm-2 in the south and the central Bay of Bengal, Cyclone Asani was not able to intensify beyond a Category 1 cyclone.

The high easterly wind shear in the Bay of Bengal, which exceeded 20 knots, prevailed throughout Asani’s lifespan, effectively disallowing the convection to symmetrically organise around the cyclone.

As a result, one of the fundamental requirements for a cyclone to intensify was not met, which led to Cyclone Asani’s failure to intensify despite very conducive ocean conditions.

A recent trend

Through our research published in Earth-Science Reviews in 2022 and Climate Dynamics in 2021, we have seen a change in the pre-monsoon Bay of Bengal cyclones. In the last two decades (2000-2019), the average lifetime of these cyclones’ maximum intensity has decreased as compared to the earlier period (1980-1999).

Their average lifetime maximum intensity in the recent period is ~130 kmph, which is ~19 kmph lesser than the earlier period.

Furthermore, while the sub-surface temperatures in the Bay of Bengal during the pre-monsoon season have increased by ~0.7°C in the last 40 years, there has also been an increase in the wind shear over the basin in recent years. This has led to unfavourable atmospheric conditions for the cyclones to intensify.

This is in contrast to the Arabian Sea, where both the ocean and the atmosphere are becoming more and more conducive for the cyclones to intensify into stronger systems. As a result, the intensity of pre-monsoon cyclones in the Arabian Sea has increased from 100 kmph in the earlier period to 140 kmph in the recent period.

This shows that cyclones in the Arabian Sea and the Bay of Bengal are evolving differently due to the contrary changes in the ocean-atmospheric conditions in these basins, and it will be interesting to see the kind of impact this shift will have on the Indian subcontinent.



Vineet Kumar Singh and Roxy M. K., 2022, A review of ocean-atmosphere interactions during tropical cyclones in the north Indian Ocean, Earth-Science Reviews, 226, 103967, doi: 10.1016/j.earscirev.2022.103967.

Deshpande, M., V. K. Singh, Ganadhi M. Kranthi, M. K. Roxy, R. Emmanuel, & U. Kumar, 2021, Changing status of tropical cyclones over the north Indian Ocean, Climate Dynamics, 1-23.


Vineet Kumar Singh is currently pursuing his Ph.D. from the Indian Institute of Tropical Meteorology, Pune. His research is focused on understanding the characteristics of cyclones in the north Indian Ocean. His research interest revolves around developing the understanding of tropical cyclone mechanisms and creating improved techniques for cyclone prediction in the future.

This article is a guest column reflecting the author’s opinions and does not necessarily represent the official views of The Weather Channel. The article has been partly edited for length and clarity.


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