Severe storms impacted eastern Iowa Friday afternoon producing an EF2 Tornado near Fairbank and damaging winds elsewhere. When the National Weather Services issues Severe Thunderstorm and Tornado Warnings for such storms, the warnings contain an estimate of storm speed and direction of travel. The featured chart presents such storm motion estimates from NWS Davenport during the summer months of June, July, and August (JJA). The warnings from Friday are highlighted with the red crosses. The blue lines attempt to show where the most frequent combinations of storm speed and motion reside. The bullseye appears to be somewhere near a storm motion from the west around 40 MPH. You can generate this chart for other months of the year and compare how the storm motion changes during the year.