Estimated Convective Winds: Reliability and Effects on Severe-Storm Climatology

Convective surface winds in the contiguous U.S. (CONUS) are classified as severe when reaching 50 kt (58 mph, 26m s^–1), whether measured or estimated.  In 2006, NCDC (now NCEI) Storm Data, from which the SPC database is directly derived, began explicit categorization of severe wind-gust reports as measured gusts (MGs) or estimated gusts (EGs).  Because of the documented tendency of human observers to overestimate wind speed, the quality and reliability of EGs (especially compared to MGs) has been challenged, mostly for nonconvective winds and controlled-testing situations, but only speculatively for bulk convective data. 

For the 10-y period of 2006–2015, a total of 150 343 quality-controlled convective-wind gust magnitudes are compared and analyzed, including 15 155 MGs and 135 188 EGs, both nationally and by geographic region.  Nonmeteorological artifacts are shown for the wind data, including pronounced “spikes” of an order of magnitude where EG values (in both mph and kt) end in the digits 0 or 5.  Results from prior wind-tunnel testing of human subjects are applied to:  1) illustrate the difference between measured and perceived winds for the severe-storm database, and 2) show the impact on the severe-wind dataset if all EGs were bias-corrected, regionally and over the CONUS.