Cyclone Arnab intensified after interacting with a lingering low-pressure system near Tamil Nadu, which IMD overlooked in its updates.
Independent platforms like Windy.com and Zoom Earth tracked the system's merger with Arnab, leading to heavy rains and gusty winds across Odisha and Andhra Pradesh, raising concerns about El Niño's impact on regional cyclonic activity.
When Cyclone Arnab made a prolonged landfall along the Andhra Pradesh coast in the early hours of October 28, 2026 it was interacting with another cyclonic system to its northeast, which the India Meteorological Department (IMD) had not acknowledged in its press release.
The IMD had indicated the persistence of a low-pressure area over the “southwest Bay of Bengal and adjoining south coastal Tamil Nadu” in its October 26 press release. However, there was no mention of the low-pressure area in the IMD’s October 27 press release.
Independent weather analysis and visualisation platforms such as Windy.com and Zoom Earth showed the continued presence of the low-pressure system alongside Cyclone Arnab. The platforms also suggested that Cyclone Arnab interacted with the low-pressure system and gained strength.
Zoom Earth showed the low-pressure system’s track until it approached the Odisha coast at around 11.30 am on October 28. Meanwhile, data from the European Centre for Medium-Range Weather Forecasts (ECMWF), as visualised on Windy.com, showed its interaction with Cyclone Arnab as late as 6 pm on October 28.
In fact, ECMWF data visualised on windy.con indicated that the low pressure area merged with Cyclone Arnab during the evening of October 28.
Independent weather analysts and bloggers have also been tracking and posting about the low-pressure system and its interactions with Cyclone Arnab.
“Seriously, seeing something like this for the first time! Cyclone Arnab is intensifying like a monster, while the earlier low pressure system that gave Tamil Nadu nearly 10 days of widespread rains is still hanging around as a separate system!” wrote independent weather analyst Ajith Kumar (Chennai Weatherman) on social media platform X (formerly Twitter) on October 27.
“ATCF has now tagged that system as Invest 90B, previously 99A. Seriously bizarre thing!! It is still lingering around Tamil Nadu's latitude, but remains far east of the coast to bring significant rains right now. If those both would have combined by now, Arnab could potentially have become an even more powerful system,” Kumar added.
ATCF stands for Automated Tropical Cyclone Forecasting System, software developed by the United States Naval Research Laboratory to automate tropical cyclone forecasting and analysis.
“Adding to the point 99A which entered Bay of Bengal and designated as Invest 90B and persisted near the Tamil Nadu coast. And around October 27, it tried to spin along the periphery of Cyclone Arnab with rapid movement,” Biswajit Sahoo, co-founder and chief executive of climate-tech startup AbsoluteMet Pvt Ltd, who posts on X as Odisha Weatherman, told Down To Earth.
“By today morning 10.00 am it crossed the coast near to Ichapuram in Andhra Pradesh. Under its influence south and coastal districts of Odisha especially Ganjam, Gajapati, Puri, parts of Khurda have witnessed gusty winds upto 80 km/hr with intense rainfall,” Sahoo added.
“But as the system was present in the periphery of Cyclone Arnab that may be the reason IMD didn’t consider it as an individual system. This 90B system also provided moisture feed to Cyclone Arnab (helped to intensify) and also one of the reason for southward movement of the cyclone,” Sahoo said.
Following the apparent merger of the two systems, ECMWF data visualised on Windy.com showed the resulting system tracking northwards across Chhattisgarh and Jharkhand towards Uttar Pradesh, potentially bringing rainfall along its path.
Meanwhile, the IMD also indicated the presence of an upper-air cyclonic circulation over the south Andaman Sea and surrounding region on October 28. Under its influence, a fresh low-pressure area could develop over the same region by October 29.
This possibility was also highlighted to Down To Earth by the weather blog Vagaries of Weather. Its analysts pointed out that several weather models suggested the system could develop into a cyclone and move towards the Odisha coast by November 1-2.
The continued activity of tropical cyclonic systems in the Bay of Bengal raises questions about the potential influence of a strong El Niño event in the equatorial Pacific Ocean on the region.