How Localized Heavy Rainfall Contributed to Roadway Debris in a Pennsylvania Injury Case
AccuWeather analyzed more than two months of weather preceding the roadway incident.
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A flooded road is impassable following heavy rainfall, Saturday, June 22, 2024, in Lincoln County, South Dakota. (AP Photo/Josh Jurgens)
Executive Summary
In a Pennsylvania roadway-related personal injury case, AccuWeather Forensic Services investigated whether heavy rainfall could have washed debris and loose material onto the road. By analyzing more than two months of weather data, forensic meteorologists identified several periods of intense rainfall, including a localized cloudburst capable of producing substantial runoff, flooding, washouts, and debris flows. The findings demonstrated why site-specific weather analysis can reveal critical conditions that monthly rainfall totals and distant weather stations may miss.
Key Takeaways
-- AccuWeather analyzed more than two months of weather preceding the roadway incident.
-- Meteorologists used surface observations, climatological records, precipitation measurements, Doppler radar, and NOAA precipitation-frequency data.
-- Seven separate days had brief rainfall rates of at least one inch per hour at the incident site.
-- One thunderstorm produced approximately 1.50 to 1.75 inches of rain in only 40 minutes.
-- Peak rainfall rates during that storm exceeded two inches per hour.
-- The localized cloudburst was estimated to have an average recurrence interval of approximately 10 to 25 years at that location.
-- The analysis concluded that rainfall of this intensity could have washed loose stones or gravel onto traveled lanes where the terrain directed runoff toward the roadway.
Investigating Whether Rainfall Contributed to Roadway Debris
AccuWeather Forensic Services was asked to determine whether heavy rainfall could have contributed to debris and loose material being washed onto a Pennsylvania roadway. The investigation focused on the weather conditions during the two months preceding the personal injury incident, with particular attention given to short periods of intense rainfall capable of generating significant runoff.
Because the final disposition of the litigation was not available, the forensic weather case study focused exclusively on AccuWeather’s meteorological investigation and findings. The objective was to reconstruct the rainfall conditions at the site and assess whether those conditions could have moved stones, gravel, or other loose materials onto the roadway.
Reconstructing Site-Specific Rainfall Conditions
AccuWeather’s forensic meteorologists reviewed surface weather observations, climatological records, precipitation measurements, Doppler radar data, and NOAA precipitation-frequency information. This combination of independent sources provided a more detailed picture of conditions at the incident location than a monthly rainfall total or data from a distant weather station could provide.
The analysis identified seven separate days when rainfall rates at the site briefly reached or exceeded one inch per hour. Even when these bursts were short, rainfall at that intensity could generate substantial runoff, especially in areas where sloping terrain directed water toward the roadway.
A Localized Cloudburst Revealed by Doppler Radar
One thunderstorm was significantly more intense than the other events studied. Approximately 1.50 to 1.75 inches of rain fell in only 40 minutes, while peak rainfall rates exceeded two inches per hour. Flooding, washouts, and debris flows were also reported throughout the surrounding area.
AccuWeather concluded that rainfall of this intensity was sufficient to wash loose stones or gravel from areas beside the roadway onto traveled lanes wherever the terrain directed runoff toward the road. The storm provided important context for evaluating the roadway conditions associated with the personal injury case.
Why Monthly Rainfall Totals Did Not Tell the Full Story
Another report associated with the litigation stated that there was no indication of unusual rainfall during the month in question. However, AccuWeather’s review of Doppler radar and other meteorological evidence identified a highly localized cloudburst that was not apparent from the broader monthly data.
The analysis determined that a rainfall event of this magnitude would occur, on average, only once every 10 to 25 years at that location. This finding illustrates why localized forensic weather analysis can be essential in cases involving roadway drainage, erosion, flooding, washouts, and debris. By reconstructing individual storms at a specific location, AccuWeather can provide attorneys with scientifically supported evidence about weather conditions and their potential effects.
Why attorneys and insurers use AccuWeather Forensics
AccuWeather Forensic Meteorologists provide objective weather reconstruction and analysis that clarify environmental conditions surrounding disputed events. Using the greatest collection of weather-related data available, including publicly available and proprietary data sets, our experts analyze historical weather records, local observation data, snow and ice conditions, precipitation history and temperature trends to support insurance disputes, accident investigations, property damage cases and other litigation.
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