It is a fact that parts of South India have been witnessing rainfall since the 28th of May. As of now, most conditions (as set by the IMD) have been met for the onset of Southwest Monsoon over Kerala, according to us.
Rainfall has now reached parts of Telangana, Rayalaseema and Karnataka, as heavy showers have been recorded over South India, including some of the major cities. This rainfall pattern has extended up to Konkan and Goa region in the last 24 hours.
Here’s a look at the rainfall figures across South India on Monday.
Andhra Pradesh – Hyderabad 47 mm, Kurnool 47 mm, Anantpur 55 mm and Ramagundam 2 mm.
Tamil Nadu – Chennai 22 mm, Karaikal 37 mm, Cuddalore 23 mm, Coimbatore 3.1 mm and Cunnoor 8.6 mm.
Karnataka – Bangalore 27.8 mm, Chitradurga 67.2 mm, Belgaum 45mm, Gulbarga 2 mm, Gadag 0.7 mm, Honawar 1.2 mm, Karwar 0.8 mm and Magalore 0.2 mm
Kerala – Punalur 4.6 mm, Kottayam 16.2, Kannur 12.6 mm, Thiruvananthapuram 5.6 mm, Kochi 10.4 mm and Alappuzha 0.5mm, Thrithala in Palakkad district 108.2 mm, Kondungallur in Thrissur district 100 mm, Ponnani in Malappuram 46.3 mm, Kuppady in Wayanad 51 mm, Cheruthazham in Kannur district 75 mm and Kasargode 34.2 mm
Konkan – Goa 11 mm and Ratnagiri 11 mm.
Among all the conditions required for the onset of Monsoon, good amounts of rain is the most important factor. Rainfall figures recorded in Kerala and Karnataka in the last few days are a clear indication that the above criteria has been fulfilled.
Monsoon usually enters Rayalaseema, Telangana and Karnataka within 4 to 5 days of its onset over Kerala and then from there it heads towards Bay of Bengal and Northeast India. This pattern has now been recorded in the last 24 hours.
While parts of Karnataka have already been witnessing heavy showers since the 28th of May, Telangana in particular observed good amounts of rain in the last 24 hours, leading to a drastic drop in temperatures, by about 9° to 10°C. Here, mercury levels were recording close to 40⁰C until last week.
Further forecasts suggest Monsoon rain is likely to continue in the southern parts of the country for 48 hours. However, the intensity of rain could diminish.
Considering that this is an El Nino year, we can not depend entirely on set methods to indicate the onset date of the Monsoon. “Effects of El Nino are well known and well-studied by weathermen across the globe by now, but what changes it might bring in the onset dates of Southwest Monsoon in India are yet to be well researched”, says AVM (Retd) G.P Sharma. “El Nino in India may not just affect the overall monsoon performance, increasing or decrease rainfall in a region, it may also have a huge impact on date of onset”, he further added.
Continuous rain in Kerala from the 28th of May till now, therefore indicates that monsoon arrived before the official date of 1st of June.
Weather records show, two El Nino years, 2012 and 2009 saw changes in the onset dates of Southwest Monsoon over Kerala. While in 2009 the date of onset was nine days before the official onset date, i.e. 23rd May, it was delayed in 2012 by about four days and arrived on the 5th of June. 2009 was a drought year with 27% below normal rainfall whereas 2012 was a year with 7% below normal rains.
This year, another change possibly brought about by El Nino, is the onset of Southwest Monsoon over Sri Lanka which was delayed by about nine days. The onset was declared yesterday as opposed to the normal onset date of 25th May. Skymet had also predicted staggered monsoon rains across East and Central India this year, signs of which are beginning to arise already.
It is indeed necessary to expect variation in weather in India due to the El Nino phenomenon as it further amplifies the truant nature of monsoon, leading to excess or deficit rainfall in different pockets. And this is why other than focusing only on effects of El Nino on the 'amount' of rainfall, there is a serious need to revise the official dates set years ago for the onset of Southwest Monsoon.
Ways of establishing the arrival of Monsoon in India are still primitive and orthodox. It would scientifically not be wise to expect a copy book onset of monsoon in India every year. Relying on fixed dates of onset or on parameters set decades ago leads to too much confusion in this day and age, hence it is imperative revise techniques and to rethink the indicators of Monsoon onset.