Supercell lightning is a product of a supercell thunderstorm, a rotating thunderstorm which has higher than normal electrical activity. These storms produce the most intense and dangerous light shows on earth with the most highly charged cloud to ground lightning of any warm weather thunderstorm.
Most thunderstorms produce in-cloud lightning, sometimes called intra-cloud or sheet lightning, but supercell’s have such high electrical charges that they produce mostly cloud to ground lightning, although on rare occasions you can witness ground to cloud or cloud to cloud lightning with bright fractal streams of lightning arching from one cloud to another. Supercell lightning is unique in the fact that it produces a positive charge rather than the negative charge that occurs with most thunderstorms. This fact has inclined the scientific field to intensify studies of supercells and have found a definite relationship between the lightning flash speed, ground-strike polarity and the intensification of the storms themselves. Lightning data has also shown that LP (Low Precipitation) storms produce mostly positive strikes while HP (High Precipitation) storms produce mostly negative strikes. Positive ground strikes occur very frequently in supercell storms with flash rate times being extremely fast holding a higher current with longer current durations.
Supercells have enough energy to form out away from other storms but can and often do form within squall lines where multicell storms have lined up in a series. Supercells are also deviants, the energy that they contain can cause extreme changes in direction very quickly and sporadically. These storms are considered the most dangerous type of storms due to the extreme weather they can produce with some supercells having holes called “lightning holes”, where updrafts are found and precipitation is minimal, that form just before it becomes severe. Supercell thunderstorms have continuously rotating updrafts from the beginning and are notorious for producing large, long lived tornadoes making them responsible for most of the significant tornadoes in the United States. Supercell lightning may be the main indicator of an impending tornado with an increase in flash speed having been documented as a supercell makes its characteristic right turn before producing a tornado. The lightning’s polarity changes from positive to negative as the tornado touches down with lightning flash rates also increasing with the presence of hail inside the storm.
Supercell lightning and the storms that produce it are enabling researchers to understand more about how a storm forms and intensifies. The use of supercell lightning data could improve warning times for severe storms and lead to better, more accurate forecasts.
http://www.srh.noaa.gov/jetstream/tstorms/tstrmtypes.htm
http://www.srh.noaa.gov/jan/?n=local_research_positive_strike
http://www.publicaffairs.noaa.gov/releases2000/may00/noaa00r511.html
http://www.crh.noaa.gov/crh/ssd/pdf/ta04-01.pdf
http://www.nssl.noaa.gov/observations/ltmap.php
