LAMY, N.M. — Every summer evening at 7 o’clock, Thomas Ashcraft receives a personalized weather report. It is monsoon season, and he is getting advice from a meteorologist in Colorado on where to look for the massive thunderstorms that erupt over the western High Plains.

Armed with sensitive cameras and radio telescopes, Mr. Ashcraft hunts for sprites — majestic emanations of light that flash for an instant high above the thunderheads, appearing in the shapes of red glowing jellyfish, carrots, angels, broccoli, or mandrake roots with blue dangly tendrils. (Weather buffs call the tall, skinny ones “diet sprites.”) No two are alike.

And they are huge — tens of miles wide and 30 miles from top to bottom. But because they appear and vanish in a split-second, the naked eye tends to perceive them only as momentary flashes of light. It takes a high-speed camera to capture them in detail.