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Met dept: Monsoon onset over Kerala delayed by a week

The onset of southwest monsoon over Kerala signals the arrival of monsoon over the Indian subcontinent and represents beginning of rainy season over the region.

Written by Nisha Nambiar | Pune | Updated: May 16, 2016 11:06 am
monsoon, monsoon in india, monsoon prediction, monsoon onset, monsoon onset date, monsoon in kerala, weather prediction, weather in india, rainfall in india, rainfall delay, rainfall delay india, weather update, weather news The southwest monsoon advances over the Andaman Sea normally around May 20 with a standard deviation of about one week.


The onset of the southwest monsoon over Kerala, which signals the arrival of monsoon over the Indian subcontinent, will be delayed by a week, the India Meteorological Department (IMD) said Sunday.

In a statement, the IMD said the statistical model forecast it uses suggests that the monsoon onset over Kerala is to be delayed slightly and is likely to set over Kerala on June 7, with a model error of plus or minus four days.

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S Pai, Deputy Director General (Climate division), Pune IMD, said: “Of the six predictors, five predictors that are used in the statistical model indicate delayed monsoon over Kerala. These predictors indicate the seasonal transition. Pre-monsoon showers to monsoon showers show lagging in these predictors, so we say that there is delay of onset over Kerala. However, we cannot rule out the possibility of a depression forming in the Bay of Bengal which will help monsoon to set over south Andaman Sea around May 17 and over north Andaman Sea on May 20. This will cause increased rainfall activity in the southern peninsula.”

Read Also: Monsoon delayed but not likely to be deficient

The onset of southwest monsoon over Kerala represents the start of the rainy season. The normal date for monsoon onset over Kerala is June 1. Since 2005, IMD has been issuing operational forecast for the onset using an indigenously developed statistical model with a model error of plus or minus 4 days.

The model uses the following six predictors: minimum temperatures over north-west India, pre-monsoon rainfall peak over south peninsula, outgoing long wave radiation (OLR) over South China Sea, lower tropospheric zonal wind over southeast Indian Ocean, upper tropospheric zonal wind over east equatorial Indian Ocean, and outgoing long wave radiation (OLR) over the south-west Pacific region.

The forecast of the monsoon onset issued in the last 11 years (2005-2015) except 2015 proved to be correct. The verification of the forecast for the last five years is given below (see box).

“We have had that one exception as there was a system in the Arabian Sea last year so the monsoon got delayed,’’ Pai said.

The verification of the forecast for the last 5 years is given below.

Year Actual Onset Date Forecast Onset Date
2011 29th May 31st May
2012 5th June 1st June
2013 1st June 3rd June
2014 6th Juner 5th June
2015 5th June 30th May

The southwest monsoon advances over the Andaman Sea usually around May 20 with a standard deviation of about one week. The IMD has observed strong convective activity over the equatorial Indian Ocean for the last several days. A well-marked low pressure area has formed over the Indian Ocean which will concentrate into a depression and move north-westward.

The IMD said that the conditions are becoming favourable for the onset of southwest monsoon over Nicobar Islands, south Andaman Sea and parts of south Bay of Bengal around May 17 and advancement over the entire Andaman Sea close to its normal date.

It also said that past data suggests that there is no association of the date of monsoon advance over the Andaman Sea either with the date of monsoon onset over Kerala or with the seasonal monsoon rainfall over the country.
Meanwhile, private weather forecasters issued an early forecast date of May 29. Last week, Skymet issued the onset date as May 29. Other forecasters said a delay in monsoon is noticed in the years after El Nino year.


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  1. K
    May 15, 2016 at 9:44 am
    Welcome news for south block for rains!hope if not believing scientific series than belief in the almighty gods.
    1. Yogesh Sharma
      May 15, 2016 at 2:13 pm
      This is a very dangerous reality. Natural calamities are very regular havoc in this nation……….But for certain reason people and government both are responsible for such disasters…….. One rain has failed the system. Governments and people have destro the entire environment………….. One can see environment, floods, draught related departments, offices, NGOs, activists, etc., in every street and corner but doing nothing. Environment , floods, draught , have become a money minting Taksal. All are one in looting and destroying the environment but do nothing……….. There are some very easy and simple ways to control such disasters such as floods, droughts, heat etc., 1-Plant and protect trees. 2- Increase and protect forests and forests cover. 3-Increase and protect wet land and wet land area. 4-Construct and protect dams, check dams and ponds. 5-Harvest rain water. 6-Link Rivers. 7-Use solar energy. 7-Generate power by Hydro power projects.8-Control potion. 9-Remove encroachments from river beds and wet lands.. And say good by to floods, droughts, water scarcity, famine and deaths, avoid heat and global warming and enjoy good environment. Dams, River linking and rain water harvesting are the permanent solution for floods and droughts, heat and warming.
      1. A
        May 15, 2016 at 1:14 pm
        Monsoons are like Indian Railways. Most of the Times late!
        1. B
          Bombay Splash
          May 15, 2016 at 12:30 pm
          Nahi, aaj kal, allah kafiron pe pani nahi barsata. He has become intelligent in last few years (since NaMo has become PM). He too is protesting against the rising intolerance!!! ;-)
          1. D
            Dharmendra singh
            May 15, 2016 at 12:29 pm
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