Not all lightning requires rain – it can also occur under dry conditions (or during volcanic eruptions). As rain falls, it can encounter a very dry air mass and may evaporate before reaching the ground. Consequently, dry lightning is notorious for sparking wildfires. Under normal thunderstorm conditions, precipitation would immediately extinguish any spark from the lightning. However, these dry lightning events are often accompanied by wind and can easily spread a small smoldering flame.
Unsurprisingly enough, Bruce Springsteen wrote a song a few years back titled “Dry Lightning.” Too bad his mentions of the weather phenomenon completely miss the point. It could very well be typical thunderstorm lightning in the distance:
The only thing in sight
Is dry lightning on the horizon line
Just dry lightning and you on my mind
Dry lightning most often occurs over the Western United States and can easily be predicted and tracked. One tracking program, at OC Weather, is updated every minute. This is a good thing, considering the latest (8/21/09) NWS statement for Southern Califiornia:
…THREAT OF THUNDERSTORMS THIS AFTERNOON THROUGH SUNDAY FOR SOUTHWEST
MOST OF THE MOISTURE WILL INITIALLY BE CONFINED TO THE MID AND
UPPER LEVELS OF THE ATMOSPHERE THROUGH TONIGHT…WITH THE LOWER LEVELS
REMAINING FAIRLY DRY. THIS WILL RESULT IN THE POTENTIAL FOR DRY LIGHTNING
STRIKES AND GUSTY WINDS WITH THUNDERSTORMS THROUGH TONIGHT…BRINGING
HEIGHTENED FIRE WEATHER CONCERNS TO THE REGION. BY SATURDAY…THE
AIR MASS MOISTENS…BRINGING AN INCREASED CHANCE OF MEASURABLE PRECIPITATION
ACROSS SOUTHWEST CALIFORNIA…ALONG WITH THE POTENTIAL FOR BRIEF HEAVY
Remember, it’s spelled ‘lightning’ and not ‘lightening’!