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Posted at 10:45 AM ET, 07/30/2009

Cloud-to-Cloud Lightning Puts on a Show

By Kevin Ambrose

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An expansive area of cloud-to-cloud lightning over Washington this past Saturday night. By CWG photographer Kevin Ambrose.

The most common type of lightning associated with a thunderstorm is cloud-to-cloud lightning. This type of lightning never reaches the ground and is often best viewed after a thunderstorm has exited the area, or has missed an area. Cloud-to-cloud lightning will often produce a vivid light show, visible in the sky for many miles away from the parent thunderstorm. This was the case on Saturday evening, with a frequent cloud-to-cloud lightning show as storms moved east of D.C.

What causes cloud-to-cloud lightning? Keep reading for more photos and discussion...

An interesting display of cloud-to-cloud lightning over the Tidal Basin, April 3, 2006. By CWG photographer Kevin Ambrose.

Once enough electric charge has been accumulated in a growing storm, a lightning bolt can occur. Lightning bolts normally travel from cloud to cloud (CC) or from cloud to ground (CG). Most storms produce more CC than CG flashes -- about twice as many in the typical storms we see around here, and about six times more in tropical storms.

Cloud-to-cloud lightning behind the Washington Monument, August 27, 2003. By CWG photographer Kevin Ambrose.

Exactly what triggers cloud-to-cloud lightning is still unknown and is an area of continued research. Having watched thunderstorms for years, I find that as a thunderstorm is rapidly growing and intensifying, there are frequent cloud-to-ground strikes. As the thunderstorm matures, and even starts to collapse, I see more cloud-to-cloud lightning. I've also noticed that certain sectors of a thunderstorm produce cloud-to-ground strikes while other sectors seem to have more cloud-to-cloud lightning. Thunderstorms go through cycles of growth and collapse and this may partly explain this observation.

By Kevin Ambrose  | July 30, 2009; 10:45 AM ET
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One question here: Is it possible sometimes to hear the thunder from cloud-cloud lightning, since a number of folks seem to hint that audible thunder means cloud-to-ground lightning. My opinion is that LOUD thunderclaps are almost certainly cloud-ground, but I can't be so sure about all those fainter rumbles I'm always hearing in thunderstorms.

Additionally is cloud-cloud presently detected by any of the available lightning detection services? I have my suspicions about this since many more "bolts" show up on Vaisala maps than on either StrikeStar U.S. or NALDN maps. Hence, I'm tending to conclude that Vaisala, like AM "sferics", tends to register ALL lightning strokes, while the other sevices tend to concentrate on the more dangerous cloud-to-ground strokes.

Speaking of lightning detection services, WWLLN, based in Seattle, Washington [a location not particularly noted for its thunderstorms!] has good coverage maps of world-wide thunderstorm activity, chiefly at temperate and tropical latitudes, but WWLLN also covers higher latitudes in North America and Europe. I believe the strikes they record are mainly cloud-to ground. Outside North America, the Czech Hydrometeorolgical Institute provides good lightning detection coverage for Central Europe, due largely to the fact that the Tatras, Beskids, and neighboring Carpathian ranges in the Czech and Slovak Republics and nearby countries have some of the highest thunderstorm frequencies in Europe. In fact the Slovak national anthem states that "the High Tatras flash with lightning and echo with thunder".

Posted by: Bombo47jea | July 30, 2009 12:15 PM | Report abuse

Great photos, Kevin. I've seen some amazing CC lightning while flying above thunderstorms, especially at night.

Posted by: Ann-CapitalWeatherGang | July 30, 2009 12:27 PM | Report abuse

Another interesting thing I've noticed is that lightning and thunder tends to be more evident when a thunderstorm is approaching, passing by without a lot of rain at one's location, or retreating, than when it is actually raining heavily at one's location. Thunder is particularly evident as a storm is retreating, and this is probably the basis for the "thirty-minute rule" [Don't go outside until 30 minutes after the last clap of thunder.] Occasionally very loud "bangs" occur during a retreating storm; these may be nearby thunderclaps from very powerful "positive" cloud-ground strokes from the tops of retreating Cb clouds.

Tropical cyclones don't always produce a lot of lightning when mature, but frequent lightning may be indicative of strengthening eyewall activity. While over the central Gulf, Katrina was producing far more lightning than is normally seen in a major hurricane. This lightning occurred while Katrina was at Category 4 to 5 near the deep pool of warm water in the Central Gulf. Heavy thunderstorms often occur on the fringes of strong hurricanes and are generally more frequent in the southeast quadrant of the storm.

Posted by: Bombo47jea | July 30, 2009 12:44 PM | Report abuse

As for the cause of all types of lightning, it seems to involve mainly positive/negative charge separation in ice crystals buffeted by turbulence in cumulonimbus clouds. This is why the tallest clouds in summer contain most of the lightning.

In addition, areas of electrical charge in clouds induce opposite charges on the ground, or vice versa, accounting for the majority of "negative" cloud-to-ground strokes observed.

Posted by: Bombo47jea | July 30, 2009 1:03 PM | Report abuse

Bombo47jea: On rare occasions, I have heard loud thunder from cloud-to-cloud lightning, but it more common to hear the lower volume, rolling thunder. The cloud-to-cloud lightning bolt can span a great distance across the sky and, if it is very close overhead, the thunder will be loud. Other portions of the bolt that are farther away will be heard at different times, giving the effect of rolling thunder.

Posted by: Kevin-CapitalWeatherGang | July 30, 2009 2:37 PM | Report abuse

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