Upward Electrical Discharges From Thunderstorm Tops
A variety of storm top electrical discharges have been observed using several types of low-light imagers, film, and the human eye. Recently, a video recorded an unprecedented, bright blue upward discharge from a tropical thunderstorm top near Puerto Rico. The event reached the base of the ionosphere. The horizontal dimensions of cloud top discharges can range from 100 m to several kilometers. Upward extents vary from 100 m to 70 km. Shapes include “points” of light, upwardly flaring trumpets, and narrow, vertical, lightning-like channels, some topped with expanding blue, flame-like features. Visual appearances range from brilliant white lightning-like channels to a grainy, almost particulate appearing jets of dim blue light, and sometimes as a blue flame within which a brilliant white channel appears. The classical blue jet is at the lower limit of human night vision whereas some upward discharges have been clearly seen during daylight. Cloud top “pixies” last no longer than 16.7 ms, whereas upward lightn...