1.4 Warning Techniques for Rain, Flood, Sea level, Wind

Often joking about weather forecasting is a common practice to criticize the language of freezing. Kerala is one of the most troublesome regions for weather forecasting and has numerous restrictions, in fact. Kerala receives very high rainfall in monsoons every year. Kerala has two significant Monsoon season, southwest monsoon begins by the end of May or June and northeast monsoon in the long stretch of October and November.

The South West Monsoon from June to September is the rainiest season in Kerala. About 60 to 70 percent of the precipitation received by the state is through the southwest monsoon. In the southern part of Kerala, the rainfall is 70-100 cm in the southwest monsoon, while in the northern region it reaches 250-300 cm. The windward side of the Western Ghats gets exceptionally high precipitation ranging between 250cm and 400 am. Kerala receives 100 cubic km of freshwater during the southwest monsoon. Unfortunately, a major part of this is flowing towards the Arabian Ocean.

From October to December, the north-east monsoon receives an average of 40-60 cm of precipitation in Kerala. In contrast to the southwest monsoon, the northeast monsoon is characterized by more rainfall in the southern part of Kerala and less in the north. Thiruvananthapuram district receives 60-80 centimetres of rainfall while Kasaragod and Kannur district receives an average rainfall of 10-20 cm. Also, the northeast monsoon rarely stops in some years. 2016 was one such year. 20% of the normal northwest monsoon season in Kerala was not received. The afternoon thunderstorms are the peak of the season. It is followed by summer rains, and frequent low pressure and cyclone that occasionally form in the Bay of Bengal and the Arabian Sea. During the summer monsoon season, thunderstorms are wreaking havoc.

Rainfall is not a common occurrence in Kerala. Sometimes, a village does not need to rain totally. In the case of summer showers, the same village may rain it in some places and there may be no rainfall elsewhere. Rainfall in Kerala generally falls within the meteorological mesoscale range. The mesoscale is an intermediate scale between those of weather systems and of microclimates, on which storms and other phenomena occur where horizontal dimensions generally range around 5 kilometers to several 100 kilometers. Monsoon and Cyclone considered as a synoptic system, a horizontal length scale of the order of 1000 kilometers. The precipitation because of low pressure and monsoon in Kerala is considered in mesoscale and less precipitation is considered in the micro-scale.

IMD has issued a necessary severe weather warning, in that warning related to rainfall, thunderstorm, wind, and low-pressure cyclones are particularly important during monsoon season.