Second Phase Of Monsoon Onset Starts, Central And Eastern Parts May Get Covered

Southwest Monsoon has advanced over the south Peninsula covering the states of Kerala, Tamil Nadu, Karnataka, and Goa. The stream swept entire Northeast India in one go. It also covered large parts of Maharashtra, Andhra Pradesh, and Telangana during the 1st phase of onset between 01st and 15th June. Monsoon made an early entry into Gujarat but traveled at a low pace on the eastern side of the country. By now, it should have covered the entire Odisha, West Bengal, and half wat through to Chhattisgarh, Bihar, and Jharkhand.

The second phase of monsoon onset spans between the 16th and 25th June.  Unlike in phase 1, where the monsoon travels south to north over Peninsular India along with northeastern parts, 2^nd phase rolls largely from east to west covering East India and Central parts. The Bay of Bengal(BoB) branch during this phase is more active than the western arm of the Arabian Sea. While BoB  is instrumental in covering complete state of West Bengal, Odisha, Bihar, Jharkhand,  Chhattisgarh, Madhya Pradesh, East Uttar Pradesh, Uttrakhand and large chunks of Himachal Pradesh and Ladakh, the Arabian Sea branch moves slowly from South Gujarat to Saurashtra (leaving Kutch) and brushes South Rajasthan.

The 2^nd onset phase of the monsoon is of shortest duration but covers substantial parts, including core monsoon rainfed zone of Maharashtra, Odisha, Chhattisgarh and Madhya Pradesh. The northern limit of  monsoon just stops short of Delhi and West Uttar Pradesh of the eastern arm and halts short of Kutch on the western side.  The 3^rd and final onset phase of monsoon between 26^thJune and 08^thJuly is tracked together by both the respective arms. This also is the most crucial phase and vulnerable to stagnation of monsoon stream. The monsoon has to reach the last posts of West Rajasthan during this period. This invariably is helped by the western disturbance, as the monsoon current otherwise goes rather weak before entering Jammu & Kashmir, Punjab and border areas of Rajasthan.

Monsoon 2021 was very peculiar in the last onset phase. Monsoon stream was fairly fast to cover the  southern, eastern and central parts of the country. However, the eastern arm got stuck between 13^thJune and 11^thJuly without a shake over West Uttar Pradesh and the western arm was stagnant from 19^thJune to 11^thJuly over South Rajasthan. Monsoon got bogged down on the outskirts of Delhi for nearly one month from 13^thJune to 12^thJuly 2021. Seasonal stream could travel to the last posts of West Rajasthan only on 13^thJuly 2021. Vagaries of monsoon continue to be mysterious and difficult to unfold.