The simultaneous formation of two cyclones in the Arabian Sea is a never-before-seen weather event, the India Meteorological Department (IMD) has said. The weather bureau was referring to Cyclone Kyarr, which recently brushed past the west coast and recurved towards Oman, and cyclone Maha, which developed over the past 24 hours. Under the influence of cyclone Maha, the Konkan coast, including Mumbai, is likely to get isolated very light to light showers between Friday and Saturday, the weather bureau said.
Super cyclone Kyarr and cyclone Maha developed over the past 10 days in quick succession (one followed by the other with cyclone Maha attaining cyclone status on Thursday). While cyclone Kyarr developed around October 24-25, it moved towards the Indian coast and recurved towards the Oman coast. Over the next four days, the system intensified into a super cyclone (with peak winds close to 250 km/hr) and further recurved away from the Oman and Yemen coast moving towards the Gulf of Aden. However, its impact resulted in increased wave action and minimal damage at Arabian Sea and along coastal areas of Pakistan, Oman, and Yemen. Simultaneously, another low pressure area developed into a weather depression and subsequently into a tropical cyclone (Maha) over the past 24 hours, and is likely to follow a similar track from the west coast of India towards Oman.
“There have been no past instances of simultaneous cyclones recorded in the Arabian Sea. The closest was when cyclone Megh formed a day after Chapala’s cycle ended in 2015,” said KS Hosalikar, deputy director general, western region, IMD.
In all, there have been four cyclones in the Arabian Sea this year – Vayu, Hikka, Kyarr and now Maha. The United Nations Intergovernmental Panel on Climate Change (IPCC) last month released its Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) that predicted a 10 times rise in global mean sea levels by 2100 with the possibility of more such cyclones in the Arabian Sea owing to global warming and rising sea surface temperatures under the current emissions scenario, leaving coastal habitats at critical risk. “Based on global studies, it has been detected that the intensity and frequency of tropical cyclones is increasing over Arabian Sea but the attribution for these cyclones due to impacts of climate change is with low confidence. The reason for these two cyclones appearing at the same time is unknown,” said Mrutyunjay Mohapatra, director general, IMD.
There are six parameters (three dynamic and three thermodynamic) that lead to the formation of cyclones, said Mohapatra. “Thermodynamic ones include rising sea surface temperatures, relative humidity in middle troposphere, and instability in the atmosphere allowing moist air to form aiding cloud formation through the help of convection. Other three dynamic parameters include – rotation of surface winds, located 5 degrees north, and lastly the strong wind shear (rapid changes in wind speed combined with direction or height of moving winds),” he said.
Independent meteorologists said the presence of the strong Indian Ocean Dipole (IOD) – an ocean-atmosphere phenomenon with difference in sea surface temperatures, characterised by cooling in parts of Indian Ocean and leading to enhanced rain – led to the formation of two cyclones at the same time. “Even after the southwest monsoon, the Arabian Sea has been very active, giving unseasonal rain to the west coast and the reason is the IOD, which is at a very high value for October. The IOD heats up the western Indian Ocean, creates a lot of convection in the Arabian Sea, and in this case, did not allow the Madden Julian Oscillation – a rain bearing system that travels across the globe and triggers storms at sea owing to increased moisture – to propagate, leading to this rare weather event,” said Sridhar Balasubramanian, associate professor, department of mechanical engineering and associate faculty, IDP Climate Studies, IIT- B.
He added that cyclone Maha is likely to help coastal communities. “As the cyclone skirts along the coast, it will increase fish count owing to upwelling (bringing nutrient rich water to the surface), which will help the fishing community in coming days,” said Balasubramaniam.
