Southwest Monsoon has failed to arrive at mainland Kerala, so far. Earlier, skymet had predicted its likely arrival on 26thMay with a margin error of +/-3days. Under the influence of cyclone Asani, cross equatorial flow did come up bringing before time arrival of monsoon over Andaman Sea. Thereafter, the progress has been incremental and the surge is still struggling to cross Gulf of Mannar and the Comorin Sea. It may move forward over these areas over the next 2 days but hitting coastline of Kerala remains uncertain.
Kerala and Coastal Karnataka had been raining pleasantly till 23rdMay. Nearly all the 14 earmarked locations registered adequate rainfall between 16th and 23rd May. However, it significantly quietened later and out of 14 stations, merely 5-6 locations have recorded requisite amount of rainfall over the last 3 days. The outgoing long wave radiations (OLR) values have also been hanging around the borderline limits. It is not at all reflecting the monsoon feel in terms of showers, clouds and delightful breeze.
One of the necessary condition for declaring onset over Kerala is when at least 60% of the available 14 stations ( >/= 9 ) report 24hr rainfall of 2.5mm or more on 2 consecutive days. OLR values also need to be under 200 watt/ sq. meter on these 2 days. Westerly winds with sufficient depth and speed are required to prevail in the specified window in the equatorial region.
Oceanic indices play significant role for the ushering of monsoon and progress, as well. La Nina conditions continue to prevail and seem favorable for the season. Skymet has summed up the situation and delay attributed : “ Numerical models which we depend on to predict the onset failed us. The negative IOD is having larger than life impact early in to the season even as a helpful La Nina in the equatorial Pacific holds promise. What happens in our backyard in the Indian Ocean has a pronounced effect on the weather than the tele-connection that the Pacific farther away may have had.”
In all probabilities, the onset over mainland may roll over to next week. There are hardly any promising indications of thunderous onset or speedy progress. Rather, it is appearing “ slow and sluggish” for the next one week, to start with.