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No. 57: May-Jun 1988

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The large-scale structure of electrical storms

Ground-based observers see only a few of the anvil-shaped clouds comprising a big electrical storm. The entire storm may stretch for hundreds of kilometers -- and it is not a simple structure.

The latest surprise is that all large electrical storms are bipolar; that is, the rare positive lightning strokes are concentrated at the northeast end of the storm complex, while the negative strokes are everywhere else along a northeast-southwest line. This bipolar structure persists for several hours, and it has been found in all North American storms analyzed so far. This insight into the structure of large electrical storms was provided by magnetic lightning detectors that have now been installed over nearly 75% of the United States.

The positive lightning strokes are of longer duration and more liable to start fires than the common negative strokes. But why are they concentrated at one end of the storm complex? R. Orville ventures that in a big mesoscale electrical storm, the prevailing winds blow the positively charged upper portions of the clouds to the northeast, thus establishing bipolarity.

(Orville, Richard E., et al; "Bipole Patterns Revealed by Lightning Locations in Mesoscale Storm Systems," Geophysical Research Letters, 15:129, 1988. Also: Anonymous; "New Lightning Theory Strikes," Eos, 69:57, 1988.)

Reference. Large thunderstorm complexes are cataloged in GWH3 in: Tornados, Dark Days. For ordering information: visit: here.

Lightning distribution across Florida Lightning distribution across Florida on February 22, 1987, 8:00-9:00pm. The plus signs designate positive lightning strokes.

From Science Frontiers #57, MAY-JUN 1988. 1988-2000 William R. Corliss

Science Frontiers Sourcebook Project Reviewed in:


  • "A sourcebook of unexplained phenomena is therefore a valuable addition to a collection of scientific literature. William R. Corliss has provided this in the past with his source books of scientific anomalies in several subjects, and now he has provided it for astronomy. He has done an excellent job of collecting and editing a large amount of material, taken in part from scientific journals and in part from scientific reporting in the popular or semi-scientific press." -- "The Mysterious Universe: A Handbook of Astronomical Anomalies", reviwed by Thomas Gold, Cornell University, in Icarus, vol.41, 1980

  • "An interesting, systematic presentation of unusual weather [..] This book is recommended for a general audience" --"Corliss, William R., Tornados, Dark Days, Anomalous Precipitation, and Related Weather Phenomena, Sourcebook Project, 1983.", revieweed in Choice, September 1983
  • "..the science is necessarily somewhat speculative, but Corliss's symthesis is based on reputable sources." -- "Corliss, William R. (Compiler). Lightning, Auroras, Nocturnal Lights, and Related Luminous Phenomena" reviwed by Joseph M. Moran, Univ. of Wisconsin in Science Books and Films, Sep/Oct 1983

  • "Before opening the book, I set certain standards that a volume which treads into dangerous grounds grounds like this must meet. The author scrupulously met, or even exceeded those standards. Each phenomenon is exhaustively documented, with references to scientific journals [..] and extensive quotations" -- "Book Review: The moon and planets: a catalog of astronomical anomalies", The Sourcebook Project, 1985., Corliss, W. R., Journal of the Royal Astronomical Society of Canada, Vol. 81, no. 1 (1987), p. 24., 02/1987