NASA Researches Storm Prediction     NASA scientists think they have found a new way to some severe storms. They have found almost a dozen cases where the number of lightning flashes increase dramatically as tornados develop. But it's not just any lightning. The type of lightning NASA is studying occurs inside clouds and isn't visible to the naked eye, at least in the daytime. The researchers from NASA's Marshall Space Flight Center use ground and space-based monitoring equipment to spot the flashes. They don't have enough data yet to say how often the intense lightning goes along with tornado formation. But they say eventually the research could improve the accuracy of tornado warnings.