Dry December pushes 14 districts into rain-deficient zone

Chennai, however, has recorded 40 cm this season against the normal of 44 cm

December 30, 2017 11:50 pm | Updated December 31, 2017 07:11 am IST - CHENNAI

CHENNAI, TAMIL NADU, 29/11/2017: Sudden rains lash the city on Wednesday evening. A scene at Anna Salai. 
Photo: R. Ragu

CHENNAI, TAMIL NADU, 29/11/2017: Sudden rains lash the city on Wednesday evening. A scene at Anna Salai. Photo: R. Ragu

With northeast monsoon coming to an end, Tamil Nadu is likely to face a deficit of nearly 9% or 10% this season. While this may still count as ‘normal rainfall’, dry weather in December has pushed 14 districts into the rain-deficient territory.

However, weak easterlies, which is the seasonal wind, may bring light rains over one or two places in coastal region of the State. Chennai too has a chance of light showers on Sunday. This may not add much to the seasonal rainfall though, said officials of the Meteorological Department.

S.B. Thampi, Deputy Director General of Meteorology, Chennai, said Tamil Nadu has recorded nearly 40 cm of rainfall against the normal of 44 cm for the season.

Tamil Nadu and Puducherry have had a better northeast monsoon this year compared to last year when the State recorded a rainfall deficit of nearly 62%. “We consider it as normal if a particular region receives rainfall that is up to 19% excess or deficit for the season. Though the season would officially end by year- end, there may be spillover impact during the first half of January,” he said.

Peculiar trend

One of the peculiar trends this year is that while one half of the State has received considerable rainfall, the other half has witnessed deficit. Districts along north coastal region such as Chennai and Nagapattinam have received excess rainfall. Cyclone Ockhi also brought in heavy spells over districts such as Tirunelveli and Kanniyakumari.

Weather expert Y.E.A. Raj said the monsoon had failed to bring adequate rainfall in several districts such as Coimbatore, Dharmapuri, Erode, Sivaganga, Ramanathapuram and Tiruchi for the second consecutive year.

Last year too Coimbatore and Dharmapuri had recorded poor monsoon. “But a good southeast monsoon this year may provide the much needed comfort to some of these districts like Coimbatore and Theni that may end up with normal annual rainfall,” he said.

Rise in groundwater

Northeast monsoon over Chennai district has been normal this year. While this has meant a good rise in groundwater table, the city reservoirs have not benefited much as catchment areas did not get much showers.

Chennai’s rainfall cannot be directly correlated to lack of water resources as it has received fairly good rainfall on many years in the past decade. This year, Nungambakkam registered an annual rainfall of 149 cm, exceeding the normal of 140 cm. Meenambakkam registered 161 cm of rainfall against the normal of 138 cm.

The northeast monsoon is volatile and influenced by various global weather factors. But, a mild La Nina , which does not favour the monsoon, had a bearing on the rainfall, experts noted.

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