and the Arabian Sea. During the 2004 post monsoon season the IMD started to name tropical cyclones within the basin, with the first one named Cyclone Onil during September 2004. During 2015 a modification to the intensity scale took place, with the IMD and WMO calling a system with 3-minute maximum sustained wind speeds between and an extremely severe cyclonic storm. A study analysing the spring season of tropical cyclones in the Bay of Bengal found increases in both pre-monsoon precipitation and tropical cyclone intensity as a result of enhanced large-scale monsoon circulation after 1979. The deepened monsoon trough in the Bay of Bengal not only affects cyclone frequency and timing, but also acts to direct more cyclones towards Myanmar. Increased anthropogenic aerosols likely contributed to such a regional climate change. Climatology Formation and frequency On average only five to six tropical cyclones form in the basin each year. Tropical cyclones form in the months of March to June and October to December, with peaks at May and November. Most of these storms form in the Bay of Bengal: either in the southeastern Bay of Bengal, or in the Andaman Sea, or as a remnant of a typhoon from the South China Sea. High sea surface temperatures and humidity makes the bay more favourable to tropical cyclone development. There are many tropical cyclones in the West Pacific; this may be another reason for increased tropical cyclogenesis in the Bay, as it shares a fair portion of the increased quota of ACE. Meanwhile, the storms in the Arabian Sea mostly form over south-eastern part of the Arabian Sea or a remnant of a tropical cyclone from the Bay of Bengal, however the frequency of cyclogenesis in the Arabian Sea is generally less, due to cooler sea surface temperature and high wind shear. However a strong positive Indian Ocean Dipole may cause an increase of tropical cyclogenesis than usual which was seen the 2019 season. Very few tropical cyclones develop in the months of June to September (Monsoon months) because of high vertical wind shear. These storms form and peak as depressions or deep depressions before making landfall in Odisha or West Bengal. Another reason is the low life span in the sea which also avoids the intensification of these low-pressure systems. Movement Most of the storms move in a north-westerly direction and starts curving either towards southwest or northeast. There's a