After a short spell of dry weather, the much-awaited northeast monsoon is likely to set in a couple of days over Tamil Nadu this year.
Meteorologists note that easterly winds that usher in the winter monsoon may return after October 24. The weather models of the European Centre for Medium Range Weather Forecast predict chances of the monsoon setting in over the southern region around October 27. Isolated rainfall activity is expected to occur in some parts of south Tamil Nadu for the next few days.
While they allow for a delay of over seven days than the normal onset time, weather experts note that the monsoon, known for its volatile nature and long dry spells, may bring heavy rainfall within a short period.
This year, a few places like Nagapattinam need 100% rainfall from northeast monsoon to meet their annual requirements. Y.E.A. Raj, former deputy director general of meteorology, said four good rain spells are sufficient to achieve a good monsoon year. Going by past data, the State has experienced consecutive years of excess rainfall or drought.
While November is considered the wettest month, there have been weather systems in December too.
Nearly 33 weather systems have crossed the Tamil Nadu coast in the past five decades since 1967 in the form of either depressions, cyclones or severe cyclonic storms.
According to the IMD, nearly 25 weather systems crossed near Chennai (about 100 km north or south of Chennai) during the monsoon.
In the past 16 years, there have been seven weather systems that crossed within 110 km of Chennai.
Sometimes, a trough or low pressure area is enough to bring good rainfall, say weather experts.
