Hail spatter refers to distinctive marks left on surfaces after a hailstorm. These marks are not always indicative of structural damage but reveal the hailstones’ path and characteristics. Observing hail spatter provides insights into a recent weather event, offering clues about hail size, density, and the storm’s direction.
Understanding Hail Spatter
Hail spatter appears as blemishes on surfaces where dirt, grime, or oxidation have been removed by impacting hailstones. Unlike physical damage like dents or fractures, spatter marks represent a cleaning effect, not a compromise to material integrity. These clean spots contrast with the surrounding weathered surface, making them noticeable.
Spatter appearance varies, often presenting as a rounded head with a tail, resembling an asteroid’s trajectory. The rounded head indicates the initial impact point, and the tail suggests the hailstone’s direction as it broke apart. These marks fade within a year or two as the cleaned surface re-oxidizes or accumulates new debris.
Spatter marks offer information about hailstones. The rounded head’s size approximates the hailstone’s diameter, especially for smaller hail. The spatter’s crispness and contrast indicate hailstone hardness; harder hailstones create sharper, more defined marks.
The Mechanics of Spatter Formation
Hail spatter forms from the kinetic energy transferred when a hailstone strikes a surface. Hailstones achieve significant velocities, with larger stones falling faster. A 1-inch hailstone falls around 50 miles per hour, and a 3-inch hailstone reaches nearly 90 miles per hour. This velocity, combined with the hailstone’s mass, determines the impact energy.
When a hailstone, especially a softer or “slushy” one, strikes a surface, it deforms or breaks apart. This impact causes the hailstone to act as a cleaning agent, dislodging accumulated dirt, dust, and oxidized material. The material properties of the hailstone and the impacted surface determine how distinct the spatter mark will be.
Hailstone density influences spatter appearance. Softer, less dense hailstones scatter more upon impact, creating larger, less defined patterns without significant structural damage. Conversely, harder hailstones still produce spatter but also cause indentations or other physical damage. The angle at which the hailstone strikes the surface affects the spatter pattern, with perpendicular impacts leading to more pronounced marks.
Identifying Hail Spatter
Identifying hail spatter involves looking for clean, discolored spots on weathered surfaces. These marks are commonly found on items accumulating grime, such as trash cans, electrical panels, siding, painted fences, and window sills. HVAC units, particularly their covers, are frequent locations for observing spatter.
When inspecting for spatter, observe the overall pattern. Hail falls randomly, so spatter marks appear in a scattered distribution rather than in straight lines or uniform clusters. The spatter mark’s shape provides clues; a rounded leading edge with a trailing “tail” indicates the hailstone’s approximate size and the storm’s direction.
Differentiating hail spatter from other marks is important. Spatter is an aesthetic change and does not involve dents, cracks, or punctures, which are signs of actual damage. Since spatter is temporary, its presence suggests a recent hailstorm, within the last one to two years. Missing spatter on an otherwise impacted surface indicates older damage.