Seven destructive tornadoes struck Oklahoma on May 24, 2011. The tornadoes were well forecast by the National Weather Service (NWS), and NSSL was in position to capture the storms in several ways.
NSSL’s dual-polarized X-band mobile radar captured the early and mature stages of the first tornado reported near Canton Lake, Okla. The data will be compared with another X-band dual-polarized radar for accuracy. This storm produced an EF-3 tornado.
The phased array radar successfully sampled a tornadic supercell every one minute as it evolved and went on to produce devastating EF-4 damage in towns west of Oklahoma City, Okla. A comparison of PAR data with the damage path shows that the radar captured rotation in the storm 12 minutes before it touched down. This tornado was on the ground for two hours with a 75-mile long track.
Visiting forecasters in the NOAA Hazardous Weather Testbed 2011 Spring Experiment found it interesting to be under the threat of tornadoes and then to be in the forecast path of them. They watched the storms out the window and on the National Weather Radar Testbed Phased Array Radar along with the area Terminal Doppler Weather Radar and the NWS NEXRAD. These radars showed the evolution of two confirmed tornadic debris balls as both storms moved towards Norman, Okla. Participants also reported the NSSL/CIMMS weather-adaptive 3D variational data assimilation system (3DVAR) products all handled the track and evolution of the storms and tornadoes very well.
The American Red Cross of Central Oklahoma began using NSSL’s Warning Decision Support System – Integrated Information (WDSS-II) to map rotation tracks of the storm and deploy their teams by 8 a.m. the next day.
And, several NSSL scientists have been in the field as part of NWS teams to survey the tornado tracks and assign EF-Scale ratings based on the damage they find. The EF-Scale is an estimate of the strength of the tornado based on damage to structures and vegetation. Preliminary results show three tornadoes out of the seven in central Oklahoma were ranked a violent EF-4.