Though Kerala received rainfall of 23.3 cm as against a normal of 29.2 cm in October 2011 registering a deficiency of 29 per cent, some of the stations such as Kochi, Thiruvananthapuram and Alappuzha received only 9.3 cm, 10.9. cm and 8.1 cm respectively .
The transition of southwest to northeast monsoon takes place in the month of October in the southern peninsula including Kochi.
The Kochi area gets a normal rainfall of 32.6 cm in the month of October, the fourth highest after June, July and August.
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The October rainfall of Kochi is 11 percent of its annual rainfall and is about two-thirds of its northeast monsoon season rainfall from October to December.
The normal pattern of rainfall in the month of October is thunderclouds develop over the ghats, move towards west and give thundershowers in the afternoon and evening on most days.
The best October rainfall during the period 1901 – 2010 was received in the year 1932 with a rainfall amount of 90.6 cm more which was more than two-and-half times the normal rainfall while the poorest October rainfall of 8.8 cm was received in the year 1924.
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In 2011, the October rainfall of Kochi is the third lowest since 1901 at 9.3 cm.
The other two years when it has been lowest are 8.84 cm (1924) and 8.88 cm (1982) respectively.
( The author is retired Director, Meteorological Centre, Thiruvananthapuram )