NWC REU 2017
May 22 - July 28



Photo of author

General Hail Occurrence Frequency in Convective Storms Using mPING Data

Stormi Noll and Kim Elmore


What is already known:

  • There is no method to discriminate between small hail and large raindrops using radar products.
  • If hail is often present, the quantitative precipitation estimation (QPE) will be negatively impacted.
  • The meteorological Phenomena Identification Near the Ground (mPING) smart phone application allows public citizens to submit reports of the weather occurring at their location.

What this study adds:

  • This study helps to determine the extent to which small hail is expected to be present in convective storms.
  • It confirms that hail cannot be detected based on composite reflectivity alone.
  • mPING reports can be used to better understand hydrometeor characteristics.


While non-severe hail is perceived as having little direct societal impact, it can negatively impact the quantitative precipitation estimation (QPE), something that can have significant societal impact. Miscalculated QPE can lead to mismanagement of emergency services, poor hydrologic forecasts, and mismanagement of water resources. By determining the proportion of convective storms that are associated with any hail but, particularly small or non-severe, we can begin to understand the extent to which QPE is affected by small hail. The current hydrometeor classification algorithms have little skill at discriminating between small hail and large raindrops. Thus choosing a threshold at which to make adjustments to QPE due to hail is difficult. We can use meteorological Phenomena Identification near the Ground (mPING) crowd-sourced weather reports to make a rough estimate of how common small hail is at the surface within convective storms. By pairing mPING data with composite reflectivity within identified storms, no clear hail/no hail threshold emerges, and so adjusting QPE based on reflectivity values is unlikely to result in much improvement in QPE.

Full Paper [PDF]