2011 has been a prolific year for major tornado outbreaks. We know of the storms that have impacted our cities and towns across the country. We also are generally familiar with the devastating outbreaks affecting cities like Joplin, Tuscaloosa, St. Louis & Raleigh. There is one outbreak though that many people overlooked because of the timing of the event. This outbreak occurred in Central Oklahoma, produced 2 EF-4 tornadoes and one 60+ mile long EF-5 tornado. However, due to the timing of the event, most of the nation’s focus was elsewhere on another community that was severely impacted.
On May 24th (2 days after Joplin), a number of tornadoes impacted central Oklahoma (NWS – Norman Event Summary). The most powerful of these was rated as an EF-5 tornado impacting the El Reno area. That storm was not only sampled by mobile and fixed weather radar, but the outer edges of the tornado actually were directly measured by the Oklahoma Mesonet station at El Reno (see images below).
The mesonet station measured a wind gust to 151mph (click on the photo to the left to visit the AMS blog). There are nearly 120 stations throughout Oklahoma as a part of the Oklahoma Mesonet. This information proves invaluable to having field verified weather observations that are directly measured. Even though this tornado was on the ground for nearly 60 miles and had a width of 1 mile, direct measurements of this nature are not usually seen. There were 9 fatalities and nearly 200 injuries with this storm.
At nearly the same time as the El Reno/Piedmont storm was hitting those areas, two other storms were rolling through Central Oklahoma, further to the Southeast. These two storms ended up tracking to less than ten miles from Norman Oklahoma where the National Weather Center is located – housing some of the nation’s brightest and best minds in severe weather research.
Additionally, the Dual-Polarization Radar at KOUN is located in Norman. This radar has the upgrade to dual polarization technology. While no surprise to those in Oklahoma, the resolution and quality of the dual-pole data has significant implications that should help to save many lives.
Also, due to the proximity of these damaging violent tornadoes to the weather radar, the radar is able to show in high enough resolution what is called a debris ball on radar. These debris balls are usually found at the end of a hook echo. [NOTE: DO NOT WAIT TO TAKE SHELTER UNTIL THIS IS ON RADAR! WHEN A TORNADO WARNING IS ISSUED TAKE IMMEDIATE TORNADO SAFETY PRECAUTIONS!].
Takeaway for Emergency Managers, GIS professionals, the media, and #SMEM crowd:
The National Climate Data Center Weather and Climate Toolkit (WCT) continues to be a go to resource for us during these types of events. The graphic below shows a radar loop (click image to view animation) of two separate storms producing EF-4 tornadoes at the same time. As the loop progresses, note where the hook echo (and debris ball) track. Additionally, see where the points have been added onto the display showing the path of these features.
Throughout this year, in EF-2+ tornadoes from supercell storms that have occurred within 50-60 miles of the radar site, and especially in the case of the violent tornadoes (EF4+), this signature has been quite evident on radar time and time again. Based on that experience, and awareness from Social Media, Broadcast Media, and National Weather Service warnings, I was able to monitor the path of this storm in realtime. In fact, I was actually traveling through Hartsfield Airport in Atlanta at the time for a conference in Colorado. The plane event had wi-fi on it and I was able to view this data as it was happening from 35,000 feet, looking out the left side of the plan AT the storms as we flew over Kansas.
The greatest takeaway though, is that the NCDC WCT allows users to place annotation points on the map. When debris ball signatures are evident in tornado warned storms, those points can be added to the map and even as a GIS shapefile. The timestamp from the radar image (shown on the right of the graphic) can be entered as the value for each annotation point, so that you can see the times when the debris ball tracked over certain areas.
While this can’t be used for identifying damage to specific structures, it can definitely help to help bring focus to an otherwise chaotic situation. These points can be connected to one another and that rotation centerline can be buffered (1/4 1/2, 3/4 mile on each side). This produces a corridor of highest potential damage that can be referenced by emergency managers to compare to the locations of 911 calls for service. These could be used by the local media to identify damage path areas that through a chopper fly-over. These could also be used by any of these entities or to identify other facilities or communities in the impact area.
In the case of Joplin, St. Louis, Raleigh, Tuscaloosa and even Greensburg from several years ago, this analysis process can be used to help identify extremely significant features from long-tracked violent tornadoes. This in turn can increase the collective awareness of the ongoing significant event which in turn allows resources to be more effectively coordinated to support the response, search and rescue, damage assessment and recovery from the event.
Each of us has a portion of the puzzle in responding to disasters in our communities. Looking at the images shown above, note how the dots on the map derived from the debris ball signatures on radar match up almost exactly with the actual confirmed path as reported by the National Weather Service several days later. By putting these pieces together in the minutes after the tornado happens (each point can be derived every 5 minutes – after the radar is updated), we can share relevant information that helps to focus data collection efforts that are needed to rapidly respond with an appropriate scope and scale.
There are many people willing to help… but we need to look at how we can share information like this more effectively with a broad community in order to facilitate their involvement in the response/recovery process so they can provide back to us the pieces of the puzzle that we are so desperately seeking.
For more information on the May outbreak, visit the National Weather Service – Norman website at http://www.srh.noaa.gov/oun/?n=events-20110524