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Storms move in a direction, and the damage they leave behind often carries a trace of that movement. Reading directional patterns in hail and wind damage is a skill that combines careful physical inspection with an understanding of how storms typically travel across a region, and it can help corroborate or raise questions about a claimed loss when compared against available weather data. In the upper Midwest, severe thunderstorms most commonly move from the southwest toward the northeast, though individual cells can and do deviate from that general tendency, which is part of why a documented storm track carries more weight than an assumption based on typical regional patterns.
Hail impact concentration tends to correlate with which elevations and slopes faced the storm as it passed, since hail generally falls at an angle rather than straight down, driven by the wind accompanying the storm cell. A roof slope facing the direction a storm approached from often shows denser impact marks than a slope on the opposite, sheltered side of the same structure, particularly on a hip roof or a home with distinct front and rear exposures. Siding damage follows a similar logic, with the storm-facing wall typically showing more concentrated impact than a wall shielded by the structure itself or by a neighboring building or dense tree line.
Wind-driven granule loss and creasing on shingles can show a directional pattern as well, often appearing as displaced granules pushed in a consistent direction across a slope, or as lifted or creased tabs concentrated on the windward edge of a roof. Comparing this pattern against storm motion data, which radar archives can help establish for a given event, gives a way to check whether the physical damage pattern is consistent with the storm being examined for that date.
Storm motion itself is not always a simple straight line across a map. A radar loop showing successive scans over time can reveal a storm cell’s actual track and any changes in direction as it developed, and some severe thunderstorms produce distinct rotating updrafts that can shift a cell’s forward motion relative to the broader system it is embedded in. Using an animated radar sequence rather than a single static image, where that level of detail is available, generally gives a more accurate read on the direction a given storm was moving over a property at the relevant time.
This kind of directional analysis is not absolute. Roof geometry, nearby obstructions, changes in wind direction as a storm cell rotates or evolves, and the possibility of more than one contributing storm over time can all complicate a simple front-and-back reading of a structure. An inspector considers directional evidence as one factor among several, including granule loss patterns, spatter on soft metals, and the broader weather record, rather than treating any single directional observation as conclusive on its own, and any resulting judgment about damage stays separate from questions of coverage that belong to the policy and the parties involved.
This article is general education about how the appraisal process commonly works. It is not legal advice, and specific procedures can vary by state and policy.
Russ Lis is a working property insurance appraiser and umpire based in Minnesota, serving clients nationwide. Contact Appraisal Resolution.