Delineation of most favorable winds for southwest monsoon rainfall along Kerala coast.

The western coastal region of India is the most dominant region that encounters the southwesterly winds that bring about 80% of rainfall over India during the southwest monsoon period (June to September). As the winds bring moisture, it can be justifiably presumed that faster winds would bring more moisture. Identification of such favorable winds could make significant inputs to prognostic models. The daily winds during each month of the southwest monsoon and that during the pre- and post-monsoon are examined for the southwestern coast of Kerala, India. It is found that higher precipitation occurs at the wind speed of 4–5 m/s during the monsoon months and at slower/weaker winds during the pre- and post-monsoon months. Further, these favorable winds are faster (5–6 m/s and 6–7 m/s) in southern Kerala in comparison to that in northern Kerala (4–5 m/s). The favorable winds over the offshore/seaward side are faster than those over the coastal areas. The precipitation is higher in the northern region than in the southern region. The direction associated with higher precipitation is east-northeast in northern Kerala and east in southern Kerala. The correlation between the winds and precipitation is higher in the northern regions than in the southern regions, indicating higher prognostic value of the wind for monsoon forecast in northern Kerala. The principal component analysis of bi-plots of precipitation shows variability profiles of winds in the different class intervals all along the coast. In general, the classes of winds that comprise principal component-1 are not associated with the winds that induce higher precipitation, while the winds that are most favorable show lower variability indicated by proximity to principal component-2. K-means clustering shows that the precipitation is found to be homogeneous in southern Kerala in comparison to that in northern Kerala. [ABSTRACT FROM AUTHOR]

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