The term ‘kalla kadal’ refers to the freak occurrence of high swell waves often triggered by storms as far away as the Antarctic region. Travelling thousands of kilometres across the ocean basin, the swell amplifies when it encounters a coastal current, a phenomenon known as remote forcing.
‘Kalla kadal’ is known to occur along the southern coast of India, mainly during the pre-monsoon period, in April and May, marked by clear weather. The flooding turns severe on the days of spring tide. Though not well documented in scientific literature, the swells occur almost every year with varying intensity.
In Kerala, fishermen use the term ‘kalla kadal’ to refer to the freak flooding when the sea water creeps in during good weather, like a thief arriving unannounced.
In February 2012, UNESCO formally accepted the term to explain the freak occurrence. The World Meteorological Organisation and the Intergovernmental Oceanographic Commission have also recognised the terminology.
