The onset of Southwest Monsoon mostly springs a pleasant shade, so different from the past few and rarely a repeat of the earlier ones. The first phase takes place in three spurts. The first knock is over the South Andaman Sea and the Nicobar Islands around 22nd May. The next stop follows within days to reach the North Andaman Sea and Sri Lanka on 26th May. The much-awaited mainland arrival of the Southwest Monsoon is announced around 01st June covering minuscule portion of the South Peninsula. Sometimes it may not strictly observe these stops and could jump or skip to reach the next.
The monsoon current arrived over the South Andaman Sea on 17th May, 5 days before its usual arrival. There were heavy rains thereafter over Sri Lanka and North Andaman Sea in association with the formation of cyclone Amphan but the NLM (Northern Limit of Monsoon) remained unchanged. Looks like, the sea conditions will be bubbling with the monsoon drivers on either side of the coastline in the next few days. Close on heels of Cyclone Amphan in the Bay of Bengal, the Arabian Sea also may respond shortly, pushing the monsoon line.
There are no linkages between arrival of Southwest Monsoon over the Andaman Sea or Kerala and overall seasonal performance. The earliest arrival of monsoon over Kerala was 18th May 2004 and the most delayed on 18th June 1972. Both years were droughts, the latter severe than the former. The earliest arrival since 2010 was 29th May in 2011 and 2018. The former one was a normal monsoon and the latter nearly drought.
The complete monsoon onset over the country takes place in three phases. The first one advances from south to north over peninsular India along with northeastern parts and the second relay the current over central and eastern parts. The third and the final push is over North India to establish the current. The first phase invariably takes a good leap just in few days but the second half of advancement is mostly in bits and pieces. This also means that the complete onset after the initial push keeps getting complicated and advances in many installments. However even these dates have hardly any strong connection with the overall performance.
The Southwest Monsoon is likely to arrive around 28th May within a margin of 2 days. The conditions are shaping up in the equatorial belt strengthening the crossflow. NLM may take one big leap to announce before time ingress.
