How Determining Raindrop Sizes Can Boost Storm Forecasts?

Even as heat wave conditions prevail over Chattisgarh, Jharkhand, Bihar, Gangetic West Bengal and Odisha, isolated thunderstorms occurred in pockets of Sub-Himalayan West Bengal, Sikkim, Assam and Meghalaya during the past twenty four to forty eight hours. The advent of storms are good news for many who are eagerly waiting for them to douse the sun baked country and smell petrichor relief.

Thunderstorms are likely to continue in isolated pockets of Northeast India while some isolated dust storms can precipitate over northwest India. Forecasts by the India Meteorological Department indicate isolated dust storms over Punjab, Haryana, Chandigarh, Delhi and West Uttar Pradesh over the next couple of days.
Dust storms (also called black storms or Kali Andhi) in northwest India and thunder storms (Nor'westers, known locally as Kaal Baishakhi) in east & northeast India are a traditional well hound of solace from heat during the scorching summer, preceding the onset of Southwest Monsoon.

But how strong a thunderstorm would be? How much rain is expected from a certain storm? Forecasts have been steadily improving over time but the prediction of severity of storms formed on land surface have been a no go area for weather forecasters till now. But not any longer.

A storm's severity depends on many factors interacting among each other including, but not limited to, temperature, humidity, jet streams, wind shear, and lo and behold, the size of rain drops. While upper air weather measurement systems have been gauging many of these factors globally, the size of the rain drops contained in clouds have been neglected.

Any person who has ever been caught in the rain can tell that rain drops differ size. The rain drops typically become heavy as they move down a cloud and the ones at the bottom are the largest (4-6 mm). Rain drops on the top are the smallest (0.5-2 mm) while the middle range is of 3-5 mm. And according to National Aeronautics and Space Administration (NASA) scientists, it is important to know what size of rain drops clouds mostly contain in order to predict the harshness of the storm effectively.

A satellite launched jointly by NASA and JAXA (Japanese Aerospace Exploration Agency) is however going to change the way storm severity is forecast by helping meteorologists ascertain the ratio of various rain drop sizes contained in a cloud. The Global Prediction Management (GPM) satellite is fitted with a precipitation radar system that images rain drops (and snow flakes) in three dimensional.

The rain drop images can be fed as data into storm prediction weather models (statistical-mathematical computer programs) and engender more accurate storm forecasting across the globe. Forecasts like 'thunder storm activity in the evening with an 80 per cent chance of 9 mm' may soon become a reality.