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![Project Vortex-99 nssl0209.jpg Project Vortex-99](/sites/default/files/styles/max_1300x1300/https/s3.amazonaws.com/s3-east-testmedia-noaa.woc.noaa.gov/dam/Photos/legacy/pl23_nssl0209.jpg?itok=CqVT95CK)
Description
Project Vortex-99. Occluded mesocyclone tornado.Occluded means old circulation on a storm; this tornado was formingwhile the new circulation was beginning to form the tornadoes which preceededthe F5 Oklahoma City tornado. Photo #2 of sequence. (Image credit: OAR/ERL/National Severe Storms Laboratory (NSSL))