According to the Indian Meteorological Department (IMD), the severe cyclonic storm will cross the coast between Nellore and Machillipatnam, close to Ongole around Friday afternoon.
The IMD has issued cyclone warning to south Andhra Pradesh and adjoining north Tamil Nadu coasts.
A bulletin by the IMD Thursday morning said Helen' over westcentral Bay of Bengal intensified into a severe cyclonic storm and lay centred about 460 km east-northeast of Chennai, 360 km east of Ongole, 260 km east-southeast of Machillipatnam and 230 km south-southeast of Vishakhapatnam.
Under its influence, rainfall at most places with heavy to very heavy rainfall at a few places would occur over coastal Andhra Pradesh commencing from Thursday forenoon. Isolated extremely heavy falls (25cm or more) would occur over south coastal Andhra Pradesh on Thursday and Friday.
Squally winds speed reaching 55-65 kmph gusting to 75 kmph would prevail along and off south Andhra coast. The wind speed would gradually increase upto gale wind speed of 100-110 kmph, gusting to 120 kmph at the time of landfall.
The IMD has warned that storm surge of about 1 to 1.5m height would inundate the low lying areas of Nellore, Prakasham, Guntur and Krishna districts at the time of landfall.
The control room numbers are 040-23456005, 23451043
Sea condition will be rough to very rough along and off south Andhra coast. Extensive damage to thatched roofs and huts and minor damage to power and communication lines was expected due to uprooting of trees.
Fishermen have been advised not to venture into the sea. The authorities have hoisted warning signals at all ports along Andhra coast.
The state government has alerted all coastal districts, especially south coastal districts. The district collectors were directed to evacuate people from low-lying areas close to the coast.
A control room to monitor the situation has been opened at the state secretariat in Hyderabad. The control room numbers are 040-23456005, 23451043.
Nellore District Collector N. Srikant held a meeting with officials to review the situation. He said 69 habitations in 11 'mandals' were identified as low-lying and the people were being evacuated. Two teams of National Disaster response Force (NDRF) were positioned in the district.
NDRF personnel have also reached Prakasam district. The authorities had taken up evacuation of people from 28 villages to relief camps.
Heavy rains were lashing Rajahmundry and other parts of East Godavari district since Thursday morning. Tidal waves washed away a part of sea wall at Uppada, flooding beach road and affecting the vehicular traffic.
'Helen' is threatening Andhra coast even as the state is yet to recover from the massive damages caused by 'Phailin' and heavy rains last month.
Andhra Pradesh has nearly 1,000 km long coastline and the nine district faces cyclone threats every year, especially between September and November.