The anomalous winter thunderstorms of the Hokuriku Coast


  • T. Takeuti,

  • M. Nakano,

  • M. Brook,

  • D. J. Raymond,

  • P. Krehbiel


Multistation electric field change measurements have confirmed earlier findings that lightning ground strokes in the Hokuriku winter storms generally lower positive charge to earth. Only one out of eight flashes involved the ‘normal’ negative strokes commonly found in summer storms. The mode of discharge appears to favor the continuing current type: eight out of twelve strokes to ground were followed by a continuing current. Despite the ‘abnormal’ stroke polarity, the Hokuriku storms appear to exhibit a normal dipolar structure (positive charge uppermost), although the dipole is apparently severely tilted in the direction of the wind shear. A crude estimate of charge height based upon one negative cloud-to-ground flash and one positive flash locates the negative charge below the positive charge in a cloud system whose bases are at 400 m and radar tops are at 7.5 km. The reason for the occurrence of dominantly positive return stroke flashes in these winter storms remains unclear.