Here are the latest developments:
The storm, packing wind speeds of upto 120 kilometres per hour, is likely to cross the southern Andhra Pradesh coast between Nellore and Machillipatnam, according to the Indian Meteorological Department (IMD).
Heavy to very heavy rainfall has been predicted at a few places over north coastal Andhra Pradesh and the adjoining Guntur, Krishna and West Godavari districts of south coastal Andhra Pradesh in the next 48 hours. Isolated heavy showers have also been forecast for the Rayalaseema and Telangana regions.
The Met department has warned of a storm surge of about 1 to 1.5m height that could inundate the low-lying areas of West and East Godavari, Krishna, Guntur and the adjoining areas of Prakasam district at the time of landfall.
Around 25,000 people have been evacuated from low-lying areas, reports Associated Press quoting an official.
Fishermen, too, have been warned against venturing into the sea. Authorities have hoisted warning signals at all ports along the state's coast.
Chief Minister Kiran Kumar Reddy has directed the chief secretary to closely monitor the situation in coordination with collectors of all coastal districts.
Teams from the National Disaster Response Force (NDRF) have already been moved to Nellore and Prakasam districts. The National Disaster Management Authority (NDMA) has also rushed six teams to the region.
A control room to monitor the situation has also been opened at the state secretariat in Hyderabad. The control room numbers are 040-23456005, 23451043.
The weather department has clarified that Helen's intensity would be "much less" than cyclone Phailin, which slammed into the Odisha coast on October 12, bringing in its wake torrential rains and wind speeds of over 200 kilometres per hour in the state and in north coastal Andhra Pradesh.
Andhra Pradesh has a nearly 1,000-kilometre-long coastline and the nine districts there cyclone threats every year, especially between September and November.
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