Even as the remnants of Cyclone Arnab weaken over central India, weather officials are tracking a fresh low-pressure system over the Andaman Sea that could bring a new round of heavy rain to coastal Andhra Pradesh in the coming days. The India Meteorological Department said the system formed on Thursday morning and is expected to strengthen into a depression over the Bay of Bengal by October 31, keeping the eastern coast on alert barely days after Arnab's landfall.
The new system took shape over the south Andaman Sea at around 5.30 am on Thursday, October 29, under the influence of an upper-air cyclonic circulation. It remained over the same region at 8.30 am, according to the IMD's Amaravati office.
Forecasters expect it to move west-northwestwards and become a well-marked low-pressure area over the south Andaman Sea and adjoining Andaman and Nicobar Islands by Friday, October 30, and then concentrate into a depression over the southeast Bay of Bengal and adjoining areas of the Andaman Sea by October 31.
Officials in Amaravati said the system would "most likely" affect Andhra Pradesh, a state still counting the cost of Arnab. The IMD has already forecast heavy rain at isolated places in coastal Andhra Pradesh on November 1, 2 and 3, and weather experts say conditions over the Bay of Bengal are turning favourable for further intensification, possibly into a cyclonic storm.
If it strengthens, the system could head for the coast somewhere between Chennai and Andhra Pradesh, bringing heavy rain on November 1 and 2.
The timing is unwelcome for a coastline that has only just begun to recover. Arnab crossed the Andhra Pradesh and Yanam coasts between Bapatla and Visakhapatnam early on October 28 as a very severe cyclonic storm, with sustained winds of 125 to 135 kilometres per hour and gusts reaching 150 kilometres per hour. The landfall process was completed by 8 am that day, but the storm's rain bands continued to drench a wide swathe of eastern and central India as it moved inland.
By Thursday morning, Arnab had weakened into a depression over south Chhattisgarh and adjoining south Odisha. At 8.30 am on October 29, its centre lay near latitude 19.4 degrees north and longitude 81.9 degrees east, about 40 kilometres north-northwest of Jagdalpur in Chhattisgarh, 180 kilometres southwest of Titlagarh in Odisha and 310 kilometres southwest of Sambalpur.
It had moved nearly northwards at about 18 kilometres per hour over the previous six hours, and the IMD said it was very likely to weaken further into a well-marked low-pressure area over north Chhattisgarh and adjoining northwest Odisha by Thursday evening.
The rainfall left behind by Arnab has been substantial. In the 24 hours ending at 8.30 am on Thursday, there was widespread rainfall over north Andhra Pradesh, northeast Telangana, Chhattisgarh, Odisha, Jharkhand and Gangetic West Bengal, with heavy to very heavy rain at a few places and extremely heavy rainfall of 21 centimetres or more at isolated places over south Odisha and north Andhra Pradesh.
Heavy to very heavy rain was also recorded at isolated places over north Odisha, and heavy rain at isolated places over northeast Telangana, Chhattisgarh, Jharkhand and Gangetic West Bengal.
In Odisha, the storm's passage left a trail of disruption. News reports tracking the cyclone's aftermath noted that around 300 villages in Ganjam district were marooned, a reminder of how quickly floodwaters can isolate communities even after a cyclone's winds have eased. In Andhra Pradesh, the damage to infrastructure has been severe.
State Energy Minister Gottipati Ravi Kumar said in West Godavari district that the very severe cyclonic storm had inflicted a loss of at least 500 crore rupees on the state's electricity infrastructure alone, a figure that underlines the scale of the repair task facing the state government.
Weather experts have also been studying how Arnab behaved as it approached the coast. A low-pressure system lingering off Tamil Nadu may have fed extra moisture into the cyclone, helping to sustain its rain bands as it neared Andhra Pradesh, experts said. However, they were clear that the two systems did not merge: there was no indication of a Fujiwara interaction, the phenomenon in which two nearby cyclonic systems rotate around each other.
The IMD had earlier noted an interaction between Arnab and a low-pressure area over the southwest Bay of Bengal, but its advisories did not describe the event as a Fujiwara merger.
The new Andaman Sea system is now the focus of attention, and forecast models do not yet agree on its future. Most ensemble and artificial intelligence-based models indicate that the circulation will move northwestwards and weaken within the next two days, according to reports of the IMD's assessment.
Several models in the Global Forecast System group, however, suggest further intensification, with some indicating that the system could become a deep depression and others raising the possibility of a cyclonic storm. That uncertainty is normal at this stage of a system's life, but it means coastal administrations cannot afford to stand down.
For residents of coastal Andhra Pradesh, the message is one of watchfulness rather than alarm. The system is still in its early stages, and its track and intensity will become clearer over the next 24 to 48 hours. But with the state already dealing with damaged power infrastructure, waterlogged areas and displaced communities, even a moderate spell of heavy rain could complicate relief and restoration work.
State disaster management officials will be watching the IMD's bulletins closely, particularly the updates on whether the system concentrates into a depression over the southeast Bay of Bengal as forecast. Fishermen, farmers and people living in low-lying coastal areas are the most exposed if the system intensifies and moves towards the coast, and advisories in the coming days are likely to spell out precautions for each group.
The sequence of events also illustrates a pattern familiar to forecasters in the Bay of Bengal during the post-monsoon cyclone season. One system barely clears the coast before another begins to organise over the Andaman Sea, fed by warm sea surface temperatures and favourable atmospheric conditions.
October and November are historically the most active months for cyclones in the Bay, and the back-to-back systems this week are a reminder of why coastal states maintain their alert posture well beyond a single landfall.
As Arnab's remnant fades over central India, bringing rain to West Bengal, Jharkhand and Madhya Pradesh in its final stages, attention shifts eastwards to the Andaman Sea. Whether the new system becomes a footnote or the season's next named storm will be decided by the atmosphere over the next two days. For now, the forecast is clear enough on one point: Andhra Pradesh, still recovering from Arnab, should prepare for more rain.
(Reporting based on The Hindu and Sambad English.)