Storm Study in Oklahoma Records Extreme Weather Events
On June 6 at 6:30 p.m., the last launch of more than 1400 weather balloons marked the end of field operations for the six-week Midlatitude Continental Convective Clouds Experiment, or MC3E, at the ARM Southern Great Plains site. Led by Mike Jensen, MC3E principal investigator from Brookhaven National Laboratory, and Walt Petersen, MC3E principal investigator from the NASA Global Precipitation Measurement Mission, approximately 150 researchers, students, volunteers, and SGP operations personnel joined together to ensure the success of the complex collaboration between DOE and NASA. The ARM and NASA GPM programs conducted MC3E to address scientific questions on convective systems that are of mutual interest. For DOE, convective systems have been identified as a high priority scientific uncertainty. NASA's goal was to collect detailed observations of precipitation physical characteristics toward improving GPM satellite-based precipitation retrieval algorithms.
Late spring weather in the Midwest generated some of the most severe weather ever recorded in the state of Oklahoma and produced a variety of convective cloud conditions including convective lines with trailing stratiform, widespread stratiform rain, elevated or weak convection, boundary layer clouds, and mid- or high-level clouds. All of this was captured by two research aircraft and the wide array of ground-based radars, precipitation sensors, and other instruments throughout the study domain. NASA sponsored approximately 70 ER-2 flight hours and 45 flight hours for the University of North Dakota's Citation and collected airborne data in approximately 16 different cases to include data collections for 3 priority cloud-sampling cases for DOE. These cases provide an unprecedented, comprehensive data set for studying cloud and precipitation processes and improving climate models for years to come.
Some Notable Cloud Cases
Dream Scenario: MC3E researchers defined their “dream scenario” as a well-defined line of convective storms with a large stratiform rain region propagating directly over the SGP Central Facility. On May 20, they received conditions very close to their wish, as the previous day’s forecast held true and the team put their plans in motion to take advantage of widespread convection and precipitation. As the system moved over the site, it was sampled by all the ground-based instruments and radars and sampled from above and within by aircraft flying well-defined cross sections over the Central Facility. More details are available in the MC3E blog entry, The (Almost) Dream Scenario.
Tornado Time: On the afternoon of May 23, a strong line of convective storms moved over the SGP Central Facility, bringing some of the heaviest rain and strongest winds measured during MC3E. While no tornadoes were observed at the Central Facility, there were confirmed reports at different locations. As the line moved to the northeast, a tornado was clearly observed by the new C-band scanning ARM precipitation radar about 50 km to the northeast of the SGP Central Facility (see Figure). Although a tornado circulation is clearly evident in the radar observations, no related damages were reported.
On May 24, another series of storm cells spawned numerous tornadoes that touched down in Oklahoma. One of these tornadoes passed within 1/4 mile of SGP instruments located at a small SGP “extended facility” in El Reno. Although outside of the MC3E radar domain, instrumentation at an Oklahoma Mesonet site collocated with the ARM site at El Reno recorded winds of around 150 mph and an extreme pressure drop as the tornado passed through.
A tornado from the same storm system moved toward the MC3E weather balloon launch site at Purcell, as captured on video by an MC3E radiosonde launcher. This tornado was eventually classified as an EF-5, with an intensity described as “incredible.” An EF-4 tornado is classified as “devastating” and an EF-6 as “inconceivable.” Images of the tornado aftermath at El Reno are available in Flickr, and an animation from nearby radar data is available on YouTube.
Reaching Out for Understanding
Part of doing good science is helping taxpayers understand how their money is being spent. Jensen joined collaborators from NASA during a media day at Offut Air Force Base in Nebraska to answer questions about the campaign and its various components. Along with fellow BNL researcher Scott Giangrande, Jensen also led a “science café” discussion at the public library in Norman, Oklahoma, discussing the campaign in a casual atmosphere with the group of about 20 in attendance.
And last, but certainly not least, Jensen and other members of the MC3E team took time to share their experience through a field blog, writing on topics ranging from instrument overviews and weather conditions to personnel profiles and downtime activities. All the MC3E blog entries serve as a very useful reference about the campaign.
Now the task of analyzing the data collected during MC3E begins as teams of scientists will work together to unlock information about the life cycle of precipitating cloud systems. These initial analyses will be shared at several scientific conferences later this year, including:
- the American Meteorological Society’s Conference on Radar Meteorology in Pittsburgh, Pa., in September and,
- the American Geophysical Union’s Annual Fall Meeting in San Francisco, Ca. in December. Jensen and Petersen will host a session entitled “Convective Cloud Lifecycle [sic] during the Midlatitude Continental Convective Clouds Experiment (MC3E).”