Lightning likes to strike some sites.

Lightning often seems to strike with a random pleasure of its own. Yet, on a large enough scale, there is some pattern to the flashes. A new study by two meteorologists at the National Oceanic and Atmospheric Administration (NOAA) underscores the important role local topology and weather play in determining where lightning strikes. And because of this link, the researchers say, lightning data can provide an unclouded way to track regional meteorology, especially when other tools, such as radar, are not available.

Raul Lopez and Ronald Holle of NOAA's Environmental Research Laboratories in Boulder, Colo., analyzed the location and timing of lightning flashes during June, July and August 1983 in two 300-kilometer-by-300-kilometer study regions in northeastern Colorado and central Florida. Their data came from lightning flash mapping systems that cover two-thirds of the United States and much of Canada. The researchers results, recently submitted to MONTHLY WEATHER REVIEW, show that flashes do fall into general patterns.

In Colorado, the highest densities of flashes occurred along an arc nestled against the Continental and Palmer Lake Divides and generally followed the daily patterns of rainfall and wind flow measured by other techniques during previous summers. In Florida, the pattern was more diffuse, but it appears to reflect the patterns of land and sea breezes, which in turn may be controlled by the shape of Florida's coasts. Thunderstorms and lightning, the researchers suspect, congregate where the coastline bulges toward the sea, encouraging sea breezes to converge and build up into clouds over the land.