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| Chennai |
The Northeast Monsoon that brings bulk of rain in Tamil Nadu is likely to revive over the state in next 24-48 hours. Bountiful rains are in forecast for Chennai, Tamil Nadu which may again bring the flood threat over the state.
Peninsular India observes very good rain during the Northeast Monsoon season, particularly Tamil Nadu. In fact the state being a rain shadow area, receives more rains during the Northeast Monsoon season as compared to the Southwest Monsoon season.
According to the data available with Skymet Meteorology Division in India, the coastal areas of the state receive 60% of their annual rainfall during the Northeast Monsoon period, while the interiors observe 50% of their annual rainfall. During the four-month long period (June to September) of Southwest Monsoon, Tamil Nadu receives only 317 mm of rain, while the Northeast Monsoon season from October to December gives a good 438 mm of rain in the state.
Rainfall during the Northeast Monsoon depends on atmospheric systems. Also the El Nino plays an important role in enhancing rainfall activity during this period. While its impact on the Southwest Monsoon is adverse. This time around Northeast Monsoon is expected to end with 111% rainfall of the LPA, with a probability of 88%.
Characteristic of NE Monsoon Rains
During the Northeast Monsoon season, weather systems like low pressure areas and cyclonic circulations move in lower latitudes of Bay of Bengal and reach the state across southwest Bay.
Unlike the Southwest Monsoon, where the weather systems are spread well, the Northeast Monsoon observes a sequence of weather systems. These weather systems have a characteristic of giving rain for three to four days and thereafter taking a break for a couple of days.
Rainfall in Tamil Nadu in November
Meanwhile, the state with 485 mm of rain so far has already exceeded the seasonal average of 438 mm. In November alone the state has received 352 mm of rain, which is more than the monthly average of 170 mm.
The state capital Chennai has also witnessed some very heavy rains this time. In fact, the city has received 1186 mm of rain in the month of November so far, which is three times the monthly average of 407 mm. On five occasions in November Chennai recorded three digit 24 hour rainfall. The highest being 265 mm between November 15 and 16.
Such heavy rains are not uncommon during this season. However, these spells are not sudden and can be forecast.
And with one more month of active Northeast Monsoon left, the rainfall figures in the state are expected to really shoot up. Also the cyclones which form in the Bay of Bengal have a tendency to move towards Tamil Nadu during December and give heavy to very heavy rain, particularly along the coast.
Another Heavy Spell Approaching
Meanwhile, from November 29 another spell of heavy rain is going to hit the state, particularly southern parts of Tamil Nadu. A low pressure area supported by a cyclonic circulation in the south-west Bay of Bengal will give this rain. According to meteorologists at Skymet, this system will move very slowly and stay in the region for some time. The period of intense rain would be between December 1 and December 3.
[thanks to skymet]
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