Sifting Through a Vast Archive of Data

Whether it’s a $1 billion dollar disaster or a localized thunderstorm that causes damage to a few structures, there are a bevy of tools at the disposal of a forensic meteorologist to begin piecing together what the weather was like when the storm struck. The United States has over 900 land-based Automated Surface Observing Systems (ASOS) sites operated jointly by the National Weather Service (NWS), Federal Aviation Administration (FAA), and Department of Defense (DOD). In addition, there are approximately 650 similarly reliable Automated Weather Observing System sites operated by state or local governments and other non-federal entities. While 1500+ stations may seem like enough to blanket our country, there can be sizeable distances between these stations, and the weather that happens at an ASOS/AWOS station may not reflect what the weather was just a mile or two away. Thankfully, those stations are just one tool in the toolbox of a forensic meteorologist.

The National Centers for Environmental Information (NCEI) keeps a record of quality-controlled severe weather data from across the country. The Storm Events Database contains reports from NWS surface instruments; eyewitness reports by trained storm spotters or emergency management officials; media and social media reports; and occasionally, the reports of observations teams dispatched by the NWS. This searchable database can provide a few more clues to a forensic meteorologist, and the picture may come into slightly better focus, but it’s still not sharp enough.

The United States also contains a dense network of weather radar scanning the skies every 1-5 minutes to help determine precipitation rate, precipitation type, wind speed/direction, and more. There are more than 200 combined Next Generation Weather Radar (NEXRAD) and Terminal Doppler Weather Radars (TDWR) to help fill in the gaps between in-situ observations from ASOS/AWOS stations and the reports in the Storm Events Database. A forensic meteorologist uses data from these advanced radar systems to drill down even farther into exactly what was happening at any street corner in the country at a specific minute of any day for the past decade or more.

While land-based observations, the Storm Events Database, and weather radar are three important sources of weather data, they are not the only three that can be useful for a skilled forensic meteorologist. A thorough analysis may also include retrieving data from other sources including local storm reports through volunteer organizations (CoCoRaHS); news reports; archived National Weather Service forecasts, warnings, and advisories; archived computer model data; and other climate monitoring products available from NCEI for snow, ice, flood, drought and more.