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Development of warning thresholds for one inch or greater hail in the Albany New York County warning area
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  • Alternative Title:
    Warning thresholds for one inch or greater hail in the Albany New York County warning area
  • Description:
    The National Weather Service (NWS) changed the criterion for severe hail from 0.75 in (1.9 cm) to 1.00 in (2.5 cm) on 5 January 2010. Many techniques have been developed for forecasting severe hail, such as examining echo tops of various reflectivity values, Vertically Integrated Liquid (VIL) Density, and using reflectivity echo (dBZ) heights relative to the -20°C level. However, hail forecasting techniques using these examples are all based on the legacy 0.75 in severe hail criterion. In an attempt to better warn for 1.00 in hail, 384 hail reports were examined from the NWS Albany County Warning Area (CWA) between 2005-2010. This study examined values for: the reflectivity echo height at various dBZ thresholds (50, 55, 60 and 65 dBZ), gridded and cell-based VIL, Storm Echo Top (ET), VIL Density and several other parameters at a storm-scale level. This study also calculated mean and median values for each parameter in connection with the new severe hail criterion, which would be potentially useful to a warning forecaster in an operational setting. For example, storms producing severe hail, on average, had reflectivity echo tops of 3.6-5.1 kilofeet (kft) higher than non-severe storms. Other parameters detailed in this paper can also be used in conjunction with each other to give warning meteorologists confidence of the existence of severe hail within a thunderstorm.
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