![]() lakes and the Sea of Japan appears to be related to the height of the −10☌ isotherm above the surface ( Kitagawa 1992 Michimoto 1993 Steiger et al. The likelihood that lightning flashes will occur in storms over U.S. (2009) showed that modifying model output at low levels to account for heat and moisture flux from Lakes Erie and Ontario yielded “lake induced” CAPE values in excess of 1790 J kg −1 for two lightning-producing lake-effect storms. Lightning occurs more frequently in early winter when the water is warmer, although the degree of instability required to trigger convection capable of producing lightning remains somewhat uncertain because the maximum instability is realized over water, whereas thermodynamic measurements from soundings are typically made on a downwind shoreline ( Schultz 1999). ![]() The thunderstorms that develop in this weather pattern are surface based, triggered by strong surface heat and moisture fluxes between the warm water and the colder air overriding it. East Coast ( Orville 1990, 1993), and over and downwind of the Sea of Japan during Siberian cold-air outbreaks ( Kitagawa and Michimoto 1994). 2009), in the vicinity of the Great Salt Lake of Utah ( Schultz 1999 Schultz et al. The first weather pattern is associated with cold air moving over warm water, such as over and downwind of Lakes Erie and Ontario ( Moore and Orville 1990 Schultz 1999 Lackmann 2001 Steiger et al. Together, these studies have provided an understanding of common meteorological weather patterns that support the development of wintertime thunderstorms. A significant body of work has also been compiled for winter thunderstorms occurring along the western coast of Japan. 1997 Holle and Cortinas 1998 Moore and Idone 1999 Hunter et al. Since their work, a number of cold-season thunderstorm climatologies for the United States have been developed ( Colman 1990 Holle et al. The first scientific attempt to produce a climatology of wintertime thunderstorms for the United States was that of Curran and Pearson (1971). In western literature, records of winter thunderstorms first appear in the late nineteenth and early twentieth centuries ( Herschel 1888 Butterworth 1895 Beldon 1927). Interest in wintertime lightning and thunder dates to the Han Dynasty of ancient China (206 BC–220 AD), when emperors regarded winter thunderstorms as abnormal and evil, portending invasions or natural disasters ( Wang 1980 Wang and Chu 1982). About 55% of the flashes were associated with cloud-to-ground flashes while 45% were in-cloud flashes. Over 90% of the cloud-to-ground flashes had negative polarity, suggesting the cells were not strongly sheared aloft. Radar measurements obtained in convective updraft regions showed enhanced spectral width within the temperature range from −10° to −20☌, while microphysical measurements showed the simultaneous presence of graupel, ice particles, and supercooled water at the same temperatures, together supporting noninductive charging as an important charging mechanism in these storms.Ī climatology of lightning flashes across the comma head of 16 winter cyclones shows that lightning flashes commonly occur on the southern side of the comma head where dry-slot air is more likely to overrun lower-level moist air. Updrafts within convective cells in both storms approached 6–8 m s −1, and convective available potential energy in the cell environment reached approximately 50–250 J kg −1. ![]() A second case study of a cutoff low is presented to examine the relationship between lightning flashes and wintertime convection. ![]() Lightning, when it occurred, originated from the elevated convection. A case study of a deep cyclone is presented illustrating how upper-tropospheric dry air associated with the dry slot can intrude over moist Gulf air, creating two zones of precipitation within the comma head: a northern zone characterized by deep stratiform clouds topped by generating cells and a southern zone marked by elevated convection. This paper presents analyses of the finescale structure of convection in the comma head of two continental winter cyclones and a 16-storm climatology analyzing the distribution of lightning within the comma head.
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