Monsoon arrives early in Kerala, may hit Mumbai by first week of June

The southwest monsoon hit Kerala on Tuesday, three days before its scheduled arrival, the India Meteorological Department (IMD) has said.

The onset of monsoon over the southern state marks the commencement of the four-month-long rainy season in the country.

June 1 is the official onset date for the arrival of monsoon in the country and it takes more than a month-and-half to cover the entire country.

The IMD has made a forecast of “normal” rainfall this season.

Skymet, a private weather forecasting agency and a rival of the IMD, had said that the monsoon made its arrival in Kerala yesterday.

According to the IMD, if after May 10, 60 percent of the available 14 stations – Minicoy, Amini, Thiruvananthapuram, Punalur, Kollam, Allapuzha, Kottayam, Kochi, Thrissur, Kozhikode, Thalassery, Kannur, Kudulu and Mangalore – report 2.5 mm or more rainfall for two consecutive days, the onset of monsoon over Kerala can be declared on the second day.

This is one of the main parameters for declaring the arrival of monsoon.

Besides this factor, the westerly winds must be up to 15,000 feet above main sea level and outgoing long-wave radiation less than 200 wm-2 (watt per square metre) to declare the arrival of monsoon.

All the necessary parameters were met following which the onset of monsoon over Kerala was announced, Mritunjay Mohapatra, Additional Director General, IMD said.

Typically, monsoon hits Mumbai and Maharashtra approximately two weeks after it’s arrival in Kerala.

However, the IMD weather models show a rapidly progressing monsoon after its arrival in Kerala, as a result of which Maharashtra can receive rainfall as early as June 6/7. In comparison, the monsoon had hit Mumbai on June 12 last year.

Parts of north Konkan, meanwhile, could witness pre-monsoon activity such as light rainfall by June 3 due to the low-pressure area that has developed in the south eastern Arabian Sea.