Following the 10 May 2015 tornado (EF1) near Lake City, IA, SPoRT Disasters team members began to acquire commercial satellite imagery through our partnership with the USGS. Once a request for imagery was made by folks in NWS Central Region, images hosted on USGS’s Hazards Data Distribution System (HDDS) web portal were obtained for processing and distribution to the Des Moines, IA Weather Forecast Office (WFO). Concurrently, teams from the DMX WFO were deployed to assess and survey damaged areas. As survey teams collected information from the field, damage points and polygons were uploaded to the NWS Damage Assessment Toolkit’s (DAT) beta damage editor as early as 12 May 2015.
By 14 May 2015, the Disasters team was able to process and disseminate commercial satellite imagery (in this case SPOT-6 panchromatic) to the DAT application for post-event damage assessment and verification by the office. Ground scarring and swirling (see red inset in the image below) from the tornado were evident as a linear feature moving SW to NE through the image. Once the imagery was delivered, members of the DMX office were able to corroborate their original damage polygon with ground scarring in the imagery. It was in this corroboration that surveyors noted divergence in the two paths, as highlighted by the figure below, and subsequently revised their outputs.
Kevin Skow, one of the surveyor’s from the DMX office who worked the event, provided the Disasters team positive feedback on the usefulness of this imagery with regards to their work, “…the modifications you are seeing in the DAT are a direct result of what we found in the satellite data. A second storm produced wind damage within a few miles of the actual tornado path that same night. The ground survey team thought that this damage might be from the tornado. However, the satellite data showed that the path was further to the NW. The satellite data also helped us fine tune the path north of Lake City. The satellite data has proven once again to be a great asset for our storm surveying operations.”
Even with some latency, this event demonstrates the importance of providing satellite imagery to forecast offices during (and following) severe weather. While satellite imagery cannot replace the work performed during ground surveys, this type of data has the ability to provide yet another source of information for surveyors to utilize during their response efforts.