ENSO Related Severe Thunderstorm Climatology of Northwest Missouri

Peter Browning
National Weather Service Office, Pleasant Hill MO
National Weather Service Office

1803 North 7 Highway

Pleasant Hill MO 64080
816-540-5147
816-540-5922
peter.browning@noaa.gov

An examination of severe weather reports during ENSO years are compared to a 48 year database (1950-1997) to discern the impact of ENSO on the amount and severity of reported severe weather. The database consists of reports for the county warning area (CWA) of the Pleasant Hill MO National Weather Service Forecast Office. This CWA is comprised of 44 counties in Northwest Missouri and adjacent portions of Northeast Kansas. Results show a relationship between the number of annual tornadoes reported and the ENSO cycle. During the 12 warm cycle (El Nino) years, the average number of tornadoes is 8.9 while the average for the 8 cold cycle (La Nina) years is 15.4. The average for all years is 11.6. The range in both warm and cold cycles is 24 and 28 respectively, indicating that any one year regardless of the ENSO cycle could contain many or few tornadoes. The median was more revealing with the warm cycle years favoring fewer tornadoes (4) while cold cycle years favored more (13.5) than the median for all years (10.5). When examining severe hail and wind damage reports, the reverse was true. On average, more severe hail and wind damage reports occurred during the warm cycle years than during the cold cycle years. An analysis of the warm and cold cycle years and the severity (strong tornadoes, large hail) of the severe weather are also examined. Variations in the duration and intensity of ENSO cycles are also compared to account for the wide variability in the data from one warm (cold) cycle year to the next.