Analysis of Heat Impacts as Related to National Weather Service Extreme Heat Advisory and Warning Criteria in Eastern Iowa and Northwest Illinois

Extreme heat is a significant cause of weather-related illnesses and fatalities in the United States, causing more deaths than hurricanes, lightning, tornadoes, floods, and earthquakes combined. This study has two main goals. The first is to develop a synoptic composite of extreme heat events via an analysis of days with maximum temperatures at or above 100 °F at Moline, IL, which will aid forecaster situational awareness of these high impact events. Second, the study assesses the relationship of the heat index and local heat advisory/warning criteria to the workload of local emergency health service providers.

Results indicate that 100 °F+ days are not frequent at Moline, occurring only about one year in four. The typical synoptic pattern associated with these extreme heat episodes features a stronger than normal upper-tropospheric jet north of the area, a stronger than normal 500-hPA ridge over the central United States, and a warmer than normal lower-tropospheric heat dome to the southwest of the area with strong, thermal advection into the area. Analysis of local heat impacts, as determined by emergency services workload, suggests the criteria used for local heat advisories/warnings are adequate to indicate days of increased demand for heat-related emergency services. However, outliers are apparent and are associated with large-venue outdoor events.