North Indian Ocean cyclone season has no bounds but cyclones tend to form between April and December. Pre Monsoon season has a peak in May and post monsoon in November. During thick of southwest monsoon, the storms generally do not form in July and August. Ingress of monsoon in June and retreat in September may still find occasional tropical storms in the Indian Seas, on either side of the coastline.
Most tropical storms have reasonably long sea travel and therefore, extended life cycle beyond 4-5 days. There are exceptions of storms lasting for over a week in the Indian Seas. Cyclones forming over Bay of Bengal have recurving tracks and therefore last longer than the one in the Arabian Sea. However, there is no hard and fast rule to ascertain average duration of the storms. In addition to the life cycle, storms remain precarious of their size and extent. There are storms with a diameter of just about 100km and some other may span beyond 500km.
The recent tropical storm ‘Midhili’ over Bay of Bengal had extremely shortened life span of less than 24hours. A low pressure area had formed over west-central BoB on 14thNov 2023. It intensified to a deep depression on 16thevening over northwest BoB. The weather system intensified to a tropical storm in the early morning hours of 17thNov2023. The storm got steered parallel to the Indian coastline and headed for Bangladesh. The cyclone gathered pace and crossed Bangladesh coast near Khepupara, the same evening. The cyclone had one of the shortest life span and weakened on making landfall. Tropical storm, the 2nd in that area after ‘Mocha’, dumped very heavy rains and lashed the coastal parts of Bangladesh with gale speed winds in excess of 70kmh.
Earlier, a small size storm with a compressed life span was witnessed over BoB in 2006. Cyclone ‘Ogni’ was a small system with only 100km in diameter. This was the smallest storm on record in the basin between 1891-2007. The system had formed over Palk Strait as a cyclonic circulation and intensified in to a depression over east of southeast coast of India, on 29th October 2006. Later that day, it quickly strengthened while moving parallel to the coast, to cyclone Ogni. However, it did not sustain long because of land friction and entrainment. It weakened to a deep depression on 30thOctober and moved ashore Andhra Pradesh between Bapatla and Ongole. Later that day, it degenerated in to a remnant low. It dropped extremely heavy rainfall in Southeast India ( 770mm in Avanigadda-Andhra Pradesh). It had the distinction of smallest size (100km) and shortest life span (<18hours).
The Bay of Bengal will remain an active basin in November 2023. There is a likelihood of another storm entering Andaman Sea from Gulf of Thailand, early next week. It is rather early to have a precision forecast and the region will have to be observed very closely for any fresh development.
