Washington, Jan 3: A new research, using computer simulations, has suggested that if the size of the rain and hail drops in thunderstorms are big, they are likely to lead to the formation of tornadoes.

The research was undertaken by Nathan Snook and Ming Xue, from the School of Meteorology and Center for Analysis and Prediction of Storms, University of Oklahoma, Norman, Oklahoma, US.

One of the largest sources of uncertainty in weather prediction involves how microscale structures influence larger-scale phenomena.

For instance, previous studies have demonstrated that the structure, dynamics, and evolution of thunderstorms are very sensitive to cloud microphysical parameters.

However, those studies used resolutions too coarse to resolve tornadoes or tornado-like circulations and were therefore not able to study the sensitivity of tornadogenesis to microphysics.

Snook and Xue have now conducted simulations of severe tornadic thunderstorms using a grid of 100-meter (328-feet) spacing.

They found out that when the sizes of rain and hail drops are large, weaker cold pools due to reduced evaporative cooling/melting over smaller geographic regions result.

Such weak cold pools are found to produce conditions that enhance low-level rotation.

The authors' simulations show that strong, sustained vertical updrafts are positioned near and above the low-level circulation centers, providing strong dynamic lifting and vertical stretching to the air at the lower levels, which favors the creation of tornadoes.

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