CLOUD-TO-GROUND LIGHTNING IN HURRICANE-ANDREW

The spatial and temporal distribution of cloud-to-ground lightning was examined in Hurricane Andrew of 1992. Lightning locations available f rom the National Lightning Detection Network were superimposed on infr ared satellite images to relate lightning activity to hurricane cloud structure. A distinct radial variation occurred in time-averaged flash density, with a weak maximum in the eye wall, a region of near-zero f lash density 40 to 100 km from the center, and a steady increase to a large maximum in the outer rainbands 190 km from the center. This radi al distribution is consistent with the convective structure of mature hurricanes. Eye wall lightning tended to be episodic, occurring almost exclusively prior to and during periods of intensification of the sto rm. During these periods, negative flashes occurred several kilometers inward from the highest eye wall cloud tops, in the region of the lar gest radar reflectivity. Positive eye wall flashes, while small in num ber, tended to occur directly under the highest cloud tops. The result s are suggestive of a normal dipole in sign but outwardly tilted along the sloping eye wall. In general, hurricane flash characteristics res embled those for a background data set of nonhurricane flashes from th e same area. The exception occurred for negative flashes in the eye wa ll, which had a much smaller mean peak current than the background (25 .3 kA versus 44.9 kA).