Among all the natural disasters related to weather, tropical cyclones are the only ones which allow sufficient time for preparedness measures. Fairly accurate prediction of a tropical cyclone’s track and intensity, along with landfall timings, has surely contributed towards disaster mitigation.
More than 50% of the cyclonic disturbances (CDs) that are formed in the months of April and May, intensify into storms. A third of the Bay of Bengal CDs, and half the number of the Arabian Sea CDs, intensify into cyclones. The frequency is very less over the West Arabian Sea due to colder sea surface temperatures (SST).
The genesis and growth of weather disturbance depends on many parameters. It continues to be a tough nut to crack because of the complex dynamics of disturbances. As such, tropics remain the most challenging pocket because of rapid phase changes in the structure of weather perturbations. Favorable SST is the basic but most essential requirement for sustenance of CDs. This is closely followed by a conducive field of weak wind shear. Favourable situation is desirable not only in the peripherals of CDs but, at times, even miles away in the Indian Ocean and West Pacific Ocean.
Currently, the Bay of Bengal is witnessing favorable pattern for formation of cyclonic circulations. However, the passage of strong typhoon ‘Noul’ in the West Pacific has inhibited the development of these weather systems. A typhoon draws huge amount of energy and also governs wind pattern even in Indian basins. These powerful systems suppress growth of any small disturbance, which gets ‘killed’ even before it shows signs of emergence. ‘Noul’ is being closely followed by another possible typhoon ‘Dolphin’, presently marked as a tropical storm, in the open waters of the West Pacific Ocean.
While most typhoons in the Pacific affect Philippines, and reemerge in South China Sea to recurve and affect China and Japan, few of these do enter Andaman Sea across Laos, Cambodia and Thailand. Such events are seen mostly during southwest Monsoon season and they contribute towards formation of Monsoon depressions and low pressure areas in the Bay of Bengal. However, the weather models at Skymet do not indicate formation of any cyclone in the Indian seas in the month of May.
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