இய அர இய வாைல ஆ ைற GOVERNMENT OF மடல வாைல ஆ ைமய INDIA METEOROLOGICAL 6, க சாைல, ெசைன - 600006 DEPARTMENT ெதாைலேப : 044- 28271951. Regional Meteorological Centre No. 6, College Road, –600006 Phone: 044- 28271951.

Weather summery of for the month of September-2021

The MJO (MADDEN-JULIAN-OSCILLATION), lay over East Indian Ocean. It moved eastwards with enhanced amplitude and entered into maritime continent (Southeast Asia) and stayed over there during the entire month. Hence the phase of MJO favoured the convective activity and hence the formation of low-pressure systems over North Indian Ocean (NIO) during the month. As per global model forecasts, the neutral ENSO (EL-NINO- SOUTHERN OSCILLATION) conditions are likely to continue. Negative IOD (INDIAN OCEAN DIPOLE) is likely to continue over the Indian Ocean. Probabilistic forecast issued by IMD for September 2021 indicated that normal to below normal rainfall activity would be over Tamilnadu and the same is realized.

Weather / Synoptic conditions prevailed in Tamil Nadu and adjoining sea areas:

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On 01st September, East-west shear zone and convective activity caused moderate to heavy rainfall at a few places over Tamilnadu. During the period from 02nd to 08th September, 2021, Cyclonic circulation, Shear zone, Southwest monsoon current and convection caused moderate to heavy rainfall at a few places over Tamilnadu. The highest weekly average rainfall of 84.6 mm recorded in and lowest weekly average rainfall of 3.3 mm recorded in . During the period from 09th to 15th September,2021, no significant synoptic features were seen over Tamil Nadu and surrounding areas, however, Southwest monsoon winds and convective activity caused light to moderate rain with isolated heavy rainfall over Tamilnadu. The highest weekly average rainfall of 72.4 mm recorded in district and no rain recorded in few districts during this week. During the period from 16th to 22nd September, 2021, Cyclonic circulation, Southwest monsoon current and convection caused moderate to heavy rainfall at a few places over Tamilnadu. The highest weekly average rainfall of 135.2 mm recorded in and lowest weekly average rainfall of 5.2 mm recorded in . During the period from 23rd to 29th September, 2021, Cyclonic circulation, Southwest monsoon current and convection caused moderate to heavy rainfall at a few places over Tamilnadu. The highest weekly average rainfall of 108.8 mm recorded in and lowest weekly average rainfall of 3.8 mm recorded in .

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On 30TH September, due to convection light to moderate with isolated heavy rain occurred over Tamilnadu. Highest rainfall recorded in centimetres during September: Western ghats: Devala (Nilgiris) 16 each. In the land area: collectorate 18. Highest Maximum temperature recorded: The maximum temperatures were normal in most places and at one or two places especially in , Thoothukudi and Karur districts, the maximum temperatures were three to five degrees Celsius above their normal. Madurai airport recorded 39.8 degrees Celsius on 15th. Fishermen warnings Issued: For Southwest Bay of Bengal, Comorin area and Gulf of Mannar Fishermen warnings were issued 13 days during September 2021 advising them not to venture into sea. Reported Rainfall, Normal and its percentage departure from normal: Tamil Nadu and Puducherry as a whole recorded 117.6 mm rainfall, which is 1% less than its normal value of 118.3 mm and Puducherry recorded 124.0 mm rainfall which is 9% less than its normal value of 136.6 mm in September.

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RAINFALL STATEMENT SEPTEMBER 2021 Districts Actual (mm) Normal Departure (%) (mm) Ariyalur 149.9 132.5 13 Chengalpattu 97.1 137.6 -29 Chennai 121.2 129.5 -6 Coimbatore 213.0 120.4 77 144.6 127.7 13 Dharmapuri 91.4 164.5 -44 Dindigul 72.9 135.6 -46 Erode 73.4 105.3 -30 Kallakurichi 135.1 157.1 -14 Kanchipuram 136.3 156.1 -13 Kanyakumari 155.7 116.7 33 Karaikal 91.9 111.8 -18 Karur 105.9 102.2 4 Krishnagiri 134.9 166.3 -19 Madurai 129.1 127.6 1 121.2 109.2 11 Nagapattinam 101.6 87.9 16 Namakkal 106.1 131.5 -19 Nilgiris 178.3 172.0 4 126.6 113.2 12 Puducherry 141.5 139.0 2 Pudukottai 146.0 115.9 26 Ramanathapuram 67.8 55.5 22 Ranipet 207.0 138.4 50 Salem 171.6 154.5 11 Sivagangai 152.9 100.4 52 Thenkasi 28.2 44.7 -37 Thanjavur 132.7 114.8 16 Theni 54.9 85.6 -36 Tirunelveli 35.3 34.0 4 Tirupathur 239.1 161.8 48 Tiruppur 51.8 72.3 -28 Tiruvallur 91.0 142.4 -36 Tiruvannamalai 217.8 163.0 34 Tiruvarur 144.5 110.8 30 Toothukudi 28.0 31.4 -11 Tiruchirapalli 115.2 125.4 -8 Vellore 187.1 163.0 15 Villupuram 110.9 136.2 -19 Virudhunagar 56.0 85.4 -34 Tamilnadu 117.6 118.2 -1 Tamilnadu, Puducherry 117.6 118.3 -1 & Karaikal

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TAMILNADU DISTRICTS SEPTEMBER 2021

In Total, during June to September, Tamil Nadu and Puducherry as a whole recorded 393.4 mm rainfall, which is 17% above than its normal value of 336.1 mm and Puducherry recorded 382.7 mm rainfall which is 10% less than its normal value of 425.6 mm.

Dr. N. PUVIARASAN SCIENTIST – “E” For Deputy Director General of Meteorology Regional Meteorological Centre, Chennai

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