Why is heavy rainfall battering Kerala?

Why is heavy rainfall battering Kerala?

Subject: Geography

Section: Climatology

Concept:

Why is Kerala witnessing heavy rains?

Kerala is presently under the influence of at least three rainfall triggering weather conditions.

1. There are strong Westerly winds flowing-in from the Arabian Sea, and bringing moisture over Kerala.
2. The presence of an east-west shear zone located 10 degrees north over the southern peninsula. This vertical zone — that can prevail either in the lower, middle or upper atmospheric levels — allows active winds of high speeds to interact. This zone also allows monsoon winds to remain active, thus causing intense rainfall over the area under its influence.
3. The IMD further stated that the presence of a north-south trough running between Chhattisgarh and Comorin areas, which are located closer to south Kerala is causing widespread rainfall.

Why more rainfall this year?

The expectations of a normal monsoon in August and September are premised on the persistence of La Nina, the converse of El Nino and characterised by the cooling of the waters of the Central Pacific. The ensuing effects are expected to help bring more rain to the Indian subcontinent, unlike the El Nino which normally dries up the rain. However, the Indian Ocean Dipole, another index of significance, marked by a swing of warm waters between the eastern and western halves of the Indian Ocean, to the monsoon is expected to be negative. A negative outlook is expected to be unfavourable for the monsoon, though M. Mohapatra, Director-General, IMD, said that this was not expected to translate into a serious deficit due to the favourable effect of La Nina.