Why it's hard to track the rain

A duty officer peered into a digital screen and jotted down the reading on a notepad, a scientist ran his finger along a set of numbers and adroitly held two different coloured pens to make markings on a map of India as his colleague frowned while staring into three monitors showing different satellite images. “The low pressure is still over West Bengal,“ he muttered.A phone call broke the silence in the room. It was a resident calling to ask if it would rain the coming week.
It is that time of the year when the city awaits the onset of the monsoon.It is also the time when jokes on the weatherman and his forecasts tend to do the rounds. But weather forecasting is more than just a prediction game, as TOI learned after a visit to the Regional Meteorological Centre in the city where scientists pore over a dozen maps, scrutinise the pattern of the wind on sepia-toned images and run through stacks of numbers sent by other meteorological centres.
One of the primary functions of the national weather services is to forecast weather parameters such as rainfall, temperature, wind and humidity in a region over a particular time period. The predictions they make, although subject to ridicule, are crucial not just to the public but to various departments like aviation, fishing and agriculture.

While the forecast in most western countries are precise, Met office here may come across as being archaic.Despite having several satellites, a number of observatories in the region that comprises Andhra Pradesh, Karnataka, Kerala, Tamil Nadu, Puducherry and Lakshadweep are still minimal, say experts. “Weather and climate is a complex system where we need to worry about space observations and ground data.Despite several advancements we are unable to predict weather so well mainly because we do not have enough automatic weather stations,“ said B N Suresh, Vikram Sarabhai distinguished professor at Isro, who was in the city to deliver a lecture.
Weather forecasting is of three types -short range (two days), medium range (four-10 days) and long range (more than a month). “We are probably the only country that does long-range forecasting. We use var ious statistical techniques to predict weather, and we have data from back in the 19th century to track climatic trends,“ said Y E A Raj, former deputy director general of Regional Meteorological Centre, Chennai.The department also co-relates the data with a particular weather parameter that happened in the past to make a prediction.
He maintained that the model the department used to forecast was on par with international standards.“We are accurate in our short and long range forecast. But, it is not always easy to forecast the monsoon here, especially the northeast monsoon because it is volatile and dependent on various conditions,“ said Raj.Air pressure, temperature, mountain ranges, ocean currents and many other factors combine to produce an enormous quantity of interacting variables all of which can alter the weather to a greater or lesser extent.
The Met office has predicted a bountiful northeast monsoon this year. “This is not based on random intuition,“ said Raj. “It is based on our observation of the El Nino effect, satellite images and data collected for more than a century ,“ he said.