Heatwave

U.S. Heatwave–Circulation Relation Using NCEP Reanalysis

• Heatwaves are defined as days with U.S.-averaged 2 m temperature anomalies above the 90th percentile.
• Composite and lag analysis of 500 hPa geopotential height shows a ridge over North America associated with heat events.
• A coherent trough–ridge pattern emerges ~3–5 days prior, while longer lags are weaker and likely noise.