Between March 1 and May 21, Bihar has received 9% surplus rainfall and it is in the category of normal rains. Whereas Uttar Pradesh is deficient in heavy rainfall with a deficit of 76 percent. In fact, the activities of pre-monsoon rain and thundershowers are almost negligible over the northern plains including Uttar Pradesh. Occasional rain and thundershowers are occurring over East India. On the other hand, moderate to heavy rains are continuing over Northeast India. This is the reason why the combined rainfall surplus of Northeast and East India is 32%.
A Fresh Western Disturbance has reached over West Himalayas and its Induced Cyclonic Circulation lies over Northeast Rajasthan. From this cyclonic circulation, a trough is extending up to Meghalaya across Uttar Pradesh, Bihar, and West Bengal. Apart from this, moist winds coming from the Bay of Bengal are also increasing the moisture in the Gangetic plains.
Due to the combined effect of these weather parameters, we expect the light to moderate rain with some heavy rain over western and central parts of Uttar Pradesh and light to moderate rain over the remaining parts. Light to moderate rain may occur in Bihar till May 24.
Rainfall in these states will reduce significantly from May 25. However, East and Central Uttar Pradesh as well as Bihar are likely to receive rains once again between May 27 and 29.
It is expected to reach Northeast India before the onset of the Southwest Monsoon. We will have to wait and see if it reaches East India by the first week of June. If this happens, Bihar may receive additional rains during the first 15 days of the monsoon.