Radar-Based Assessment of the Detectability of Giant Hail

Abstract


 The occurrence of giant hail, defined as hail ≥102 mm (4.00 in) in diameter, is a relatively rare phenomenon, accounting for less than 1% of all hail reports in the United States. Despite the infrequent nature of these events, hail of this magnitude has the potential to cause extreme damage to property and a substantial threat to exposed life. The short-term prediction of these events has been challenging. For giant hail since 2005, only 7% of convective warnings and severe-weather statements issued by the National Weather Service (NWS) accurately predicted a maximum hail size ≥102 mm prior to the report, with an average underestimated size error of 55.6 mm (2.19 in).
 The objectives of this study are to determine the detectability of giant hail in convective storms and to improve advanced recognition of these events during NWS warning operations. A total of 568 giant-hail reports, gathered over a 15-y period from 1 January 1995 through 31 December 2009 throughout the contiguous United States, served as the primary database for the research. Weather Surveillance Radar-1988 Doppler (WSR-88D) data and North American Regional Reanalysis (NARR) environmental data were collected for each case. Several radar signatures were examined to assess their utility in discriminating storms most favorable for giant hail. It was found that 99% of the storms were supercells with well-organized structure. Giant-hail producing storms were characterized by median values of rotational velocities of 24 m s-1 (47 kt), storm-top divergence magnitudes of 72 m s-1 (140 kt), and 50-dBZ and 60-dBZ echo heights of 13 100 m (43 000 ft) and 10 600 m (34 800 ft) respectively. Vertically integrated liquid water (VIL)-based products, maximum reflectivity within the storm, and reflectivity within the preferred hail-growth zone showed little to no skill in discriminating between giant hail and smaller hail sizes.

When a Dust Storm Is Not a Dust Storm: Reliability of Dust Records From the Storm Events Database and Implications for Geohealth Applications

“…Previous studies have used data from the SED to analyze the reporting of other various weather phenomena (Ashley & Black, 2008 ; Bentley et al., 2002 ; Dixon et al., 2005 ; Markowski et al., 1998 ). Many found the SED to be an inconsistent and inaccurate record of severe weather (Ashley & Black, 2008 ; Ashley & Gilson, 2009 ; Black & Ashley, 2010 ; Black & Mote, 2015 ; Blair et al., 2011 ; Downton et al., 2005 ; Miller et al., 2016 ; Trapp et al., 2006 ). Others also found the reports on damage, injuries, and fatalities to be incomplete and inconsistent (López et al., 1993 ; Santos, 2016 ).…”

How Many Types of Severe Hailstorm Environments Are There Globally?

“…In subtropical South America, the majority of significant hailstorms are not from discrete storms, such as isolated supercells, but rather from organized multicell convection (Bruick et al., 2019). In contrast, the majority of hailstorms producing hail in excess of 5 cm have been found to be associated with supercells in the United States (Blair et al., 2011; Grams et al., 2012; B. T. Smith et al., 2012).…”

Environmental and Radar Characteristics of Gargantuan Hail-Producing Storms

“…Those authors found significant underprediction of hail size both in National Weather Service warnings and Storm Prediction Center watches for these giant hail cases. Similarly, Blair et al (2017) found that severe thunderstorm warnings tended to underestimate hail size for severe (.2.5 cm) and significantly severe (.5.0 cm) hail, and that the maximum hail size officially reported in the Storm Data database tended to be considerably lower than what was actually observed. Thus, a better understanding of storms that produce very large and potentially damaging hail is needed to improve our ability to forecast, detect, and warn for these hazards, and ultimately mitigate damages to property or life.…”