Monsoon to hit Kerala coast on June 3

Cyclone Mahasen likely to increase intensity of rainfall over southern peninsula

By Soma Basu
Published: Wednesday 15 May 2013

Monsoons are expected to hit Kerala on June 3. India Meteorological Department (IMD) today informed that its model suggests the date of onset of southwest monsoon over Kerala as June 3 with a model error of plus or minus four days.

Even though southwest monsoon normally advances over Andaman Sea around May 20 with a standard deviation of about one week, this year under the influence of tropical cyclone Mahasen, currently located over the central Bay of Bengal, low level cross equatorial monsoon flow has appeared over south Andaman Sea and adjoining south Bay of Bengal.
The cyclone has strengthened and deepened the cross equatorial flow and during the next few days it may lead to increased rainfall over the southern peninsula. Heavy rains are likely to lead to advance of monsoon over Andaman Sea slightly earlier than its normal date. According to IMD, past data suggests absence of any one to one association of the date of monsoon advance over Andaman Sea with the date of monsoon onset over Kerala or that with the seasonal monsoon rainfall over the country.

The onset of southwest monsoon over Kerala signals the arrival of monsoon over the Indian subcontinent and represents the beginning of rainy season over the region. From 2005 onwards, IMD has been issuing operational forecasts for the date of monsoon onset over Kerala using an indigenously developed statistical model with a model error of plus or minus four days. The monsoon forecasts for the past eight years (2005 to 2012) were correct.

According to the forecast, southwest monsoon seasonal rainfall for the country as a whole is most likely to be normal—96-104 per cent of the Long Period Average (LPA). 

Cyclonic storm Mahasen over west-central Bay of Bengal moved further north to north-eastwards at a speed of about 16 kmph and lay centred at about 850 km northwest of Port Blair, 600 km south-southwest of Kolkata, 380 km southeast of Paradip and 750 km southwest of Chittagong. It would intensify further and move north-eastwards and cross Bangladesh coast between Khepupara and Teknaff, close to Chittagong during May 16 night. Under the influence of this system, rainfall would occur at many places in Andaman and Nicobar Islands during the next 24 hrs. Mizoram, Manipur and Tripura would also receive heavy downpour on May 16 and 17. Squall with wind speeds of 40-50 kmph and reaching up to 60 kmph is likely along Andaman and Nicobar Islands during the next 24 hours. Sea condition is expected to be very rough there.

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