November is supposed to be the rainiest month in Chennai as the state receives more than 50% of its annual rainfall from the northeast monsoon. Formation of a series of low pressure system in the Bay of Bengal which turn into possible cyclones is the major reason for the rainy weather in the city during winter months (Oct – Dec). With the current cyclonic storm Helen set to hit Andhra Pradesh by tomorrow night, heavy rain is expected in Chennai. November started off on a dry note but the weather in Chennai turned extremely wet and rainy by the middle of the month. Chennai started receiving continuous showers only from 15th onwards. Below are the rainfall figures. 15th November – 11 mm 16th Nov – 124 mm 17th Nov – 43 mm 18th Nov – 0.1 mm The normal rainfall figure for Chennai in the month of November is 407.4 mm, while the actual rainfall recorded so far has only been 202.8 mm. Therefore, in spite of heavy showers in the last few days, Chennai is facing a rain deficit of over 50%. Further, the normal rainfall figures from Oct 1 to Nov 13 in Chennai is 465 mm, however the actual figure for the same period this year has only been 220.7 mm. This is deficit by about 53%. “The week is expected to be rainy for Chennai, firstly because of Cyclone Helen and then because of another system brewing over the weekend in the Andaman Sea”, says a senior Meteorologist at Skymetweather.com. Helen could give heavy to very heavy rain, between 60 to 100 mm”, he added. Current forecasts suggest that after making landfall, cyclone Helen could continue to give rain over coastal stations of Andhra and Chennai for 48 to 72hours. Afterwards, a low pressure system will appear in the Andaman Sea which will further intensify into a deep depression and again bring rain to Chennai from the 26th of November. Speaking further our meteorologist said,"We can clearly say that the remaining days of the November month for Chennai will be rainy. Though, this good amount of rain may or may not cover up the rain deficit being faced in Chennai." Sky will be cloudy to overcast this week in Chennai and winds will pick up to reach a speed of 80 to 100 kmph as cyclone Helen comes closer. Photo by Argophilia.