Between March 1 and May 21st, Bihar has received 9% surplus rainfall and it is in normal rain category. Whereas Uttar Pradesh is large rain deficient with deficiency of 76%. In fact, pre monsoon rain and thunder shower activities are almost negligible over northern plains including Uttar Pradesh. East India has been receiving occasional rain and thundershower activities. On the other hand, moderate to heavy rain continued over Northeast India. This is why the combined rain surplus of Northeast and east India stands at 32%.
A fresh Western Disturbance has approached Western Himalayas and its induced cyclonic circulation is over Northeast Rajasthan. A trough is extending from this cyclonic circulation to Meghalaya across Uttar Pradesh Bihar and West Bengal. Moreover, humid winds from Bay of Bengal are also increasing moisture over Indo Gangetic plains.
Due to the combined impact of these weather parameters, we expect light to moderate rain with few heavy spells to occur over Western and Central parts of Uttar Pradesh and light to moderate rain over remaining parts. Scattered light to moderate rain may occur over Bihar until May 24th.
The rain will reduce significantly from May 25th over these states. However, another spell of rainfall is expected between May 27 and 29 over east and Central Uttar Pradesh as well as over Bihar.
Southwest monsoon is expected to reach Northeast India before time. We have to wait and see if it reaches over East India by first week of June. If it happens then Bihar may receive surplus rain during first 15 days of monsoon.