Figure 1: Annual Distribution: All Tornadoes 1950-2008
Figure 2: Annual Distribution: Strong/Violent Tornadoes 1880-1949
Figure 3: Annual Distribution: Strong/Violent Tornadoes 1950-2008
Figure 4: Annual Distribution of Tornado Days: All Tornadoes 1950-2008
Figure 5: Annual Distribution of Tornado Days: Strong/Violent Tornadoes 1880-1949
Figure 6: Annual Distribution of Tornado Days: Strong/Violent Tornadoes 1950-2008
Figure 7: Monthly Distribution: All Tornadoes 1950-2008
Figure 8: Monthly Distribution: Strong/Violent Tornadoes 1880-1949
Figure 9: Monthly Distribution: Strong/Violent Tornadoes 1950-2008
Figure 10: Hourly Distribution: All Tornadoes 1950-2008
Figure 11: Hourly Distribution: Strong/Violent Tornadoes 1880-1949
Figure 12: Hourly Distribution: Strong/Violent Tornadoes 1950-2008
Figure 13: Monthly vs. Hourly Distribution of Tornadoes
Figure 14: Approximate Tornado Tracks (ALL) 1950-2008
Figure 15: Approximate Tornado Tracks (Strong/Violent) 1880-1949
Figure 16: Approximate Tornado Tracks (Strong/Violent) 1950-2008
Figure 17: Approximate Tornado Tracks (Violent) 1950-2008

NWS
St. Louis, Missouri

WFO St. Louis CWA
Tornado Climatology

Click on a county below for a detailed list of tornadoes in each county.
Information is updated through 8/31/2010

A List of Significant Tornado Outbreaks in the WFO St. Louis CWA
A List of Violent Tornadoes in the WFO St. Louis CWA

Tornado Climatology methodology, limitations, acknowledgements and references.

Fujita (Enhanced Fujita) Scale
Damage Intensity F0(EF0) - F1(EF1) F2(EF2) - F3(EF3) F4(EF4) - F5(EF5)
Description Weak Strong Violent
Significant
 

Yearly Distribution

Average Annual Number of Tornadoes (all intensity): 13.27
Average Annual Number of Strong and Violent Tornadoes (F2-F5): 3.28

During the 59 year period from 1950 through 2008, a total of 783 tornadoes (all intensities) were identified in the LSX CWA. Significant tornadoes accounted for 191 of the tornadoes (or 24% of the total), resulting in an average 3.28 strong or violent tornadoes per year.  There were no tornadoes reported in either 1951 or 1989.  Significant tornadoes have occurred in the LSX CWA in 8 out of every 10 years.   The 10 significant tornadoes that occurred during the extended outbreak over the weekend of March 11th and 12th helped make 2006 the year with the most F2 and greater tornadoes (16). The database indicates there has been an increase in all tornadoes, but a gradual decline in the number of significant tornadoes in the past 59 years.   The pre-1950 statistics (Grazulis, 1993) are presented for comparison. 
Tornado Climatology
Tornado Climatology
Tornado Climatology

 
All Tornadoes
(1950-2008 )
Strong/Violent Tornadoes
(1880-1949)
Strong/Violent Tornadoes
(1950-2008)
 

Yearly Distribution of Tornado Days

The LSX CWA has experienced 346  tornado days (calendar day with an occurrence of at least one tornado) and 117 significant tornado days from 1950-2008, an average of 1.98 days per year. The number of significant days has also shown a gradual decline. The pre-1950 statistics (Grazulis, 1993) are presented for comparison. 
Tornado Climatology
Tornado Climatology
Tornado Climatology

 
All Tornadoes
(1950-2008 )
Strong/Violent Tornadoes
(1880-1949)
Strong/Violent Tornadoes
(1950-2008)
  
Monthly Distribution

The four-month period from March-June contains the greatest percentage of significant tornadoes (68%; 129 out of 191) and of all tornadoes (67%; 522 out of 783), only 26% of all tornadoes which occur during this period are significant (129 out of 522). In contrast, the four-month period from November-February contains only 18% of the significant tornadoes (35 out of 191) and only 12% of all tornadoes (95 out of 783), however 37% of all tornadoes which occur during this period are significant (35 out of 95). Thus for any tornado occurrence, the greatest probability of it being significant, is during the late autumn and winter.  The pre-1950 statistics (Grazulis, 1993) are presented for comparison. 
Tornado Climatology
Tornado Climatology
Tornado Climatology
  
All Tornadoes
(1950-2008 )
Strong/Violent Tornadoes
(1880-1949)
Strong/Violent Tornadoes
(1950-2008)
  
Hourly Distribution

Tornadoes are mainly a late afternoon and evening phenomena in the LSX CWA with 69% (132 out of 191) of the significant tornadoes occurring between 300 and 1100 pm CST. Only 4% (7 out of 191) occurred between 300 and 1100 am.  The pre 1950 statistics (Grazulis, 1993) are presented for comparison. 
Tornado Climatology
Tornado Climatology
Tornado Climatology
  
All Tornadoes
(1950-2008 )
Strong/Violent Tornadoes
(1880-1949)
Strong/Violent Tornadoes
(1950-2008)
  

Monthly vs Hourly Distribution

A scatter plot showing the date/time distribution of all tornadoes yields some additional interesting results. Tornadoes that occur in the late afternoon and evening hours (300 to 1100 pm CST) during the spring (March through June) account for 46% of all tornadoes (362 out of 783) and 52% of significant tornado occurrences (99 out of 191). Occurrences outside this window tend to be spread out. What is particularly disturbing is only 5 of the 11 violent tornadoes (F-4) are in this cluster. Five of the remaining violent tornadoes occurred in the winter months (from four separate severe thunderstorm events) during the late evening and overnight hours. The most notable event struck the city of St. Louis at 140 am on February 10, 1959. This violent tornado resulted in 21 fatalities and 345 injuries.
Tornado Climatology
Tornadoes (1950-2008)
Tornado Climatology
 Approximate Tornado Tracks (All) (1950-2008)
Tornado Climatology
 Approximate Tornado Tracks (Strong/Violent) (1880-1949)
Tornado Climatology
 Approximate Tornado Tracks (Strong/Violent) (1950-2008)
Tornado Climatology
 Approximate Tornado Tracks (Violent) (1950-2008)
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