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Very Large Hailstones From Aurora, Nebraska

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The Aurora, Nebraska, hailstorm of 22 June 2003 produced some exceptionally large hailstones, and was widely publicized. Nineteen hailstones obtained from local people have been sectioned and photographed and eight are illustrated here, recording their interior layering and external appearance. They exhibit great variability, with features that are common to large hail as well as one unusual growth form: a roughly prolate external shape indicating an approximately constant falling orientation during final growth, forming large, icicle-like projections at one end. Much of the growth is wet but not appreciably spongy, as appears to be common for large hail. While a hailstone from this storm has been called the largest recorded in the United States on the basis of its longest dimension, we suggest that the most meaningful measure of hailstone size is weight. Weight is unambiguous and easily measured, and is an excellent indicator of volume for large hail. People generally think of hail as spherical and large hail but is often far from that shape; the terms “diameter” and “circumference” are therefore inappropriate, and if records of linear dimensions are to be kept, they probably should be termed “maximum length” and “maximum perimeter.”

National Center for Atmospheric Research, Boulder, Colorado

CORRESPONDING AUTHOR: Dr. Charles A. Knight, National Center for Atmospheric Research, PO Box 3000, Boulder, CO 80307, E-mail: knightc@ucar.edu

The Aurora, Nebraska, hailstorm of 22 June 2003 produced some exceptionally large hailstones, and was widely publicized. Nineteen hailstones obtained from local people have been sectioned and photographed and eight are illustrated here, recording their interior layering and external appearance. They exhibit great variability, with features that are common to large hail as well as one unusual growth form: a roughly prolate external shape indicating an approximately constant falling orientation during final growth, forming large, icicle-like projections at one end. Much of the growth is wet but not appreciably spongy, as appears to be common for large hail. While a hailstone from this storm has been called the largest recorded in the United States on the basis of its longest dimension, we suggest that the most meaningful measure of hailstone size is weight. Weight is unambiguous and easily measured, and is an excellent indicator of volume for large hail. People generally think of hail as spherical and large hail but is often far from that shape; the terms “diameter” and “circumference” are therefore inappropriate, and if records of linear dimensions are to be kept, they probably should be termed “maximum length” and “maximum perimeter.”

National Center for Atmospheric Research, Boulder, Colorado

CORRESPONDING AUTHOR: Dr. Charles A. Knight, National Center for Atmospheric Research, PO Box 3000, Boulder, CO 80307, E-mail: knightc@ucar.edu
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