Europe: Average upper-level (300hPa) winds from June 28 - July 4, 2015 amidst an ongoing heatwave across Europe. The wavy jet stream formed into an omega block, so named after its resemblance to the greek letter omega. Map based on NCEP/NCAR Reanalysis data (Text after Tom Di Liberto: Summer heat wave arrives in Europe. NOAA Climate.gov » Event Tracker, July 14, 2015 ).