Onset of northeast monsoon was announced on 21stOctober 2023. Monsoon seems to have made a mild start and the rains have been very - very limited so far. State of Kerala has witnessed scattered moderate to light rainfall. However, Tamil Nadu and Coastal Andhra Pradesh, the take off regions of winter monsoon, have largely remained silent. Except for Kerala & Mahe, all other sub divisions have observed deficient or highly deficient rainfall during the month of October. Also, it is likely to remain generally quiet till this weekend, following which, the activity will pick up, at least for Tamil Nadu and Kerala.
Withdrawal of southwest monsoon, a prerequisite for onset of northeast monsoon, was complete on 18th October clearing the way for winter monsoon. The other necessary conditions being onset of northeasterly stream along Tamil Nadu and Coastal Andhra Pradesh and establishment of seasonal low pressure over south Bay of Bengal. The flow of northeasterly winds got disrupted on account of cyclone ‘Haroon’. This tropical storm has since made landfall in Bangladesh and is likely to become insignificant, shortly. Accordingly, the seasonal northeasterly flow will resume and pick up strength as well, to accentuating the monsoon flow over entire South Peninsula.
Northeast monsoon covers five meteorological sub-divisions : Tamil Nadu & Puducherry, Kerala & Mahe, South Interior Karnataka, Coastal Andhra Pradesh and Rayalaseema. The rains invariably spill over to Coastal Karnataka, North Interior Karnataka and Telangana as well. However, northeast monsoon is the chief rainy season and lifeline for the state of Tamil Nadu. While the state receive 35% of annual rainfall (317.2mm) during the four month long southwest monsoon season, the share of northeast monsoon is bigger at 48% (438.2mm) for the duration of three months from October to December.
The early or late onset of monsoon has little bearing on the overall seasonal performance. Last three years, the onset of northeast monsoon took place on 28thOct, 25thOct and 29thOctober in 2020, 2021 and 2022 respectively. Normal date of setting of northeasterly winds over southeast Peninsula is 14thOctober and is closely followed by onset of northeast monsoon over Coastal Tamil Nadu and Coastal Andhra Pradesh by 20thOctober. Northeast monsoon has performed within normal for the last 4 consecutive years, between 2019-2022. The winter monsoon is forecast to perform normal during 2023 as well.
