The following is a partial list of key terminology (with acronyms, where applicable) related to VDE Americas’ hail risk advisory products and services.
Average annual loss (AAL). The estimated value of the expected financial loss that may occur in any given year based on severe hail events.
Cumulative distribution function. A probability distribution function that represents the probability that a selected random variable will be less than or equal to a specific value.
Freezer iceball (FIB). A laboratory-manufactured hailstone proxy with standardized physical characteristics for conducting ballistic-impact testing to published engineering standards.
Impact energy. The amount of kinetic energy of a falling hailstone, as determined by its mass and velocity, immediately prior to impact with the surface of a PV module or other object.
Naturally occurring hail (NOH). Frozen objects of nature with widely varying shapes, sizes, and material properties. The kinetic energy of NOH varies from one event to another, resulting in differences in hailstorm damage potential.
National Oceanographic and Atmospheric Administration (NOAA). A scientific and regulatory agency operating under the U.S. Department of Commerce that monitors oceanic and atmospheric conditions and forecasts weather.
Next-Generation Radar (NEXRAD). A network of high-resolution S-band Doppler weather radar stations that detects precipitation and wind jointly operated by the National Weather Service, Federal Aviation Administration, and the U.S. Air Force.
Poisson distribution. A discrete probability distribution—named after French mathematician Siméon Denis Poisson—that is used in probability theory and statistics to show how many times an event is likely to occur over a specified period.
Probable maximum loss (PML). The estimated value of the largest financial loss likely to result from a hail event within a specific period of time, based on plant location and capacity, accounting for operating assumptions and excluding insurance considerations.
Return interval (RI). The estimated amount of time between discrete events. Mathematically, it represents the value of a given quantity that is expected to be equaled or exceeded on average once every time interval (t) with an event probability in any given year of 1/t.
Severe Weather Data Inventory (SWDI). NOAA’s integrated database of severe weather records for the United States.