STORM TRACK: March 31, 1978 (Volume 1 Issue 3)

Before describing picture taking techniques, the following list explains the types and characteristics of lightning forms.

(A) Ball lightning: A rare form of lightning in which a persistent and moving luminous white or colored sphere is seen: the explanation and even existence of this form of lightning are yet, controversial. Although as a meteorologist I've looked for this phenomena for years, it continues to be very elusive. I recently corresponded with a fellow weather guesser who did have luck in viewing ball lightning. He said, 'As I was driving across the central plains, a severe thunderstorm outbreak forced me off the road, to seek shelter under an overpass. During the most intense period of the storm, with continuous cloud to ground strokes occurring all around me, one particular bolt hit a nearby wood/metal fence. A second later,. three well defined balls -three to six inches in diameter- were traveling very slowly along the top of the fence. The color varied from light, blue to light green. The smell of ozone was almost over powering. The duration of the balls lasted nearly 30 seconds before they disappeared with an explosive bang.' I asked him if what he observed may have been St. Elmo's fire. He stated that it wasn't, 'being in the navy and to sea on and off during the last twenty years, I've seen St. Elmo's fire and what I saw under that overpass wasn't that.'

Reports of sphere dimensions vary from a few inches to a yard. Duration varies from a few seconds to several minutes. Many reported cases follow a brilliant lightning flash and may be physiological in nature (after-image). Other reported cases have, however, occurred without preceding flash. Sometimes more than one sphere is seen by an observer, or a sphere is reported in the same locality by various observers. They have been reported to vanish harmlessly, to bounce from the ground or an obstruction,and pass into or out of rooms leaving -in some cases- sign of their passage such as a hole in a window pane.

(B) Forked lightning (A specialized form of streak lightning): Lightning in which many luminous branches from the main discharge channel are visible. Such branching occurs in response to local variations of space charge close to the main channel.

(C) Pearl-necklace & chain lightning: A rare form of lightning, also termed 'bead lightning,' in which variations of brightness along the discharge path give rise to a momentary appearance similar to pearls on a string.

(D) Ribbon lightning: A term applied to a minor variation of streak lightning which looks like what would be obtained if a camera were moved.sideways while photographing a stroke. It is possible for the ionized path of the lightning stroke to be blown sideways with the wind during a multiple stroke flash. A 30-milo-per-hour wind would move air laterally 44 feet in one second. The second stroke of a two stroke flash may follow the first stroke by perhaps .07 second, so that the subsequent stroke could be displaced 3 feet from the first. I have viewed this relatively rare event on several occasions. It is truly impressive, especially with 3 or more multi-flashes.

(E) Rocket, lightning: A very rare and unexplained form in which the speed of propagation of the stroke is slow enough to be perceptible to the eye. Although impossible to show with a still camera, a movie camera that runs at 54 frames-per- second could possibly show this. It seems that this lightning type depends on the characteristic (physical) of the lightning itself.

The reason why no two lightning strokes are identical is because the cloud's charge and altitude, and the air's temperature, pressure and resistance all vary. For general purposes, however, we can divide lightning into two general categories --"Hot and Cold." Cold lightning is of very short duration but with high current: it has explosive effects upon the things it strikes. It occurs most frequently on the hottest days and is responsible for the larger number of multiple stroke.", (see Fig. 1). Hot lightning has low currents of long time duration and is more apt to burn the things it hits (see Fig. 2). This characteristic is very much associated with rocket lightning.

(F) Sheet lightning: The popular name applied to a 'cloud discharge' form in which the emitted light appears diffuse, and there is an apparent absence of a main channel because of the obscuring effect of the cloud. This is the most common lightning type. Although one would think that it would not be worth photographing, interesting lightning effects can be achieved. Strange shadowing and interesting foreground objects will add a moody 3-D realism.

(G) Heat lightning: is merely lightning too far away for the thunder to be heard or the individual stroke itself to be actually seen. The light from an ordinary lightning flash can be reflected or diffused by clouds, giving the impression of a broad area of flashing light (Not nearly as vivid as sheet lightning, hence not as photographable).

"Using any 35mm single lens reflex camera, set your exposure setting to B-bulb and attach a cable release that is long enough so as not to interfere. Because exposures are taken at night, owing to better contrast between bolt and backdrop, a good tripod is a must. One can improvise by resting his camera on the ground or on a car, making certain to steady the frame while exposing. Typical film for distinct cloud to ground strokes would be High Speed Ektachrome (ASA-160 + ). These slides prove to be excellent for public viewings. 8" X 10" print copies can be made, showing very little graininess. Depending on frequency of return strokes, distance from storm and precipitation in the air, exposures at f/8 to f/16 and from 10 to 90 seconds will prove interesting. Only through experience will you be certain how long to expose. A 50mm lens will generally give best results. If the storm is very close, a wide angle 28mm lens may work out. With sheet lightning less distinct by nature, use Kodacolor II print film,(ASA 400). Try using plus-x or tri-x black and white film. Exposures at, f/2.8 to f/5.6 and from 30 to 150 seconds give good results.

Daylight lightning photos are difficult to take because of the great amount of light, even in the darkest thunderstorms. But since lightning can often be timed on a periodic basis, an exposure of 1/4 to 1 second at f/11 to f/16 may give you luck. Of course, movies during daylight hours will easily show you a good bolt, now and then.

In conclusion, every good photo requires 10 bad attempts. However, that good shot will be worth your efforts."

(Ed. Note: "LTJG" Curtis will be serving the taxpayers for the next, year at 75 deg E longitude and 7 deg S latitude somewhere in the Indian Ocean.(on Diego Garcia). He will be the Officer in Charge of the Naval Weather Service Detachment there. On the way west to depart these hallowed shores, Jan will be traveling through the Oklahoma area about May 3-6 and would like to contact someone there "about doing some storm chasing." I'm sure he has some interesting stories to share about Naval weather forecasting.)