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Met dept sees delay in southwest monsoon, Kerala to get rains on June 6



National weather agency, the (IMD), has forecast that southwest will arrive on the coast on June 6, “slightly delayed” than the normal onset date. But with a model error of four days, may hit the mainland any day between June 2 and June 10.


Private forecaster has predicted the onset to happen on June 4. Independent weather observers too expect a delayed this time.



Monsoon performance during the past five years shows that a delay is not necessarily associated with deficient rains. The best rainfall year in the last five years was 2016, and though the monsoon arrived on June 8 that year, rains were 97 per cent of normal, though not well spread across regions.


has been quite accurate in predicting the onset date. In the last 14 years, actual onset date was incorrect only in one instance.


Experts and scientists from the said that a delayed has no bearing on the advance of the over the entire country or its regional spread. Progress of sowing or agricultural output cannot be predicted or surmised from onset date either.


Current thermal circulation and convective patterns over northern and northwest India are dominated by western disturbances among others. This condition is not conducive for formation of a pressure gradient pulls the winds flowing north of the equator to India from the southwest direction.


The met department has been issuing operational forecasts for the date of monsoon onset over from 2005. An indigenously developed statistical model with a model error of ± 4 days is used for the purpose.


The model uses six parameters to get the probable onset date. They are: minimum temperatures over northwest 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 the east equatorial Indian Ocean, and OLR over the south-west Pacific region.


Delayed monsoon doesn’t mean deficient rains












Year

Forecast Onset Date

Actual Onset Date

Seasonal rainfall as % of normal

2014

5th June

6th June

88

2015

30th May

5th June

86

2016

7th June

8th June

97

2017

30th May

30th May

95

2018

29th May

29th May

91

2019*

6th June

Yet to happen

96



Source: IMD


Note: * Forecast only



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