Tamil Nadu is a rain shadow area to South West Monsoon (SWM) and nearly 32 per cent of the total annual rainfall of Tamil Nadu is received from this monsoon. Farmers of Dharmapuri, Krishnagiri, Salem, The Nilgris Kanyakumari and western parts of Vellore and Tirunelveli are most benefitted from this seasonal rainfall.
District level rainfall forecast for the forthcoming Southwest monsoon, 2017 (June to September) over Tamil Nadu was developed at Agro Climate Research Centre, Tamil Nadu Agricultural University, Coimbatore based on the Southern Oscillation Index of summer season and Sea Surface Temperature values of east pacific ocean using Australian Rainman International V.4.3.software.
The historical rainfall data collected from Tamil Nadu Agricultural University Stations were used to represent the basis for district rainfall data set. In the absence of data from research station in a particular district, data from Rainman software were used alternatively. Rainfall expected during Southwest monsoon season, 2017 with 60 per cent probability is given below
Sixty five per cent of the State will be receiving the normal rainfall during this South West Monsoon season 2017.
Normal Rainfall is expected in Salem, Namakkal, Dharmapuri, Krishnagiri and The Nilgiris districts and also for Chennai, Coimbatore, Cuddalore, Dindigul, Dindigul, Erode, Kancheepuram, Kanyakumari, Madurai, Perambalur, Pudukottai, Sivagangai, Theni, Tiruvallur, Tiruvannamalai, Villupurum and Vellore districts normal rainfall is expected.
Deficit Rainfall is expected in Nagapattinam, Ramanathapuram, Tirunelveli, Tutucorin, Tiruppur, Karur, Virudhunagar, Trichy, Thanjavur, Ariyalur and Tiruvarur districts.
For the Normal rainfall forecast districts, existing agro technologies along with weather based agro advisories and normal cropping pattern may be followed
For the Deficit rainfall forecast districts, with the available irrigation facilities, short duration less water requiring crops may be raised. This forecast can be used for making strategic agricultural farm decisions.