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.