Figure 1: Map of Tornado Track in Percy, IL October 24th, 2001
Figure 2: At 1145 AM CDT, a line of severe thunderstorms moves across the Bi-State area. Notice the severe thunderstorm (Lincoln county supercell) just northwest of Carlinville, Illinois. This supercell developed as it crossed the Mississippi River into Illinois. It stayed intact all the way into northwest Indiana, causing extensive damage along the way. The Franklin County Supercell produced large hail and damaging winds over Franklin and St. Louis counties.
Figure 3: At 1209 PM CDT, three supercells were identified across the Bi-State region. The St. Charles county supercell was responsible for the damage at Portage Des Sioux. Hail and damaging winds continued to be reported with the Franklin county supercell as it entered the far western sections of St. Louis county at this time. A new storm, exhibiting supercell characteristics is observed over northern Crawford county.
Figure 4: At 1230 PM CDT, the three supercells continued to remain intact as they moved to the northeast at speeds of 55 to 60 mph. The three storms did not spawn any tornadoes over the area.
Figure 5: At 227 PM CDT, a bow echo embedded within the larger squall line moved east-northeast at 60 mph across southern Randolph county in Illinois and northern Perry county, Missouri.
Figure 6: A closer view of the bow echo at 227 PM CDT, shows a spearhead reflectivity pattern along the leading edge suggesting accelerated storm outflow.
Figure 7: Corresponding storm relative velocity pattern shows a strong tornadic circulation (bright green 100 knots inbound velocities) adjacent to a region of darker red (27 kts outbound). This circulation, referred to as a tornado cyclone and located at the top of the spearhead echo pattern, was responsible for spawning the Percy, IL tornado.
Figure 8: The Marina at Portage Des Sioux in the extreme eastern portion of St. Charles county, Missouri was hard hit by microburst winds estimated at better than 70 mph. Several sheds and docks were destroyed. One man sustained injuries when airborne debris landed on him.
Figure 9: The Marina at Portage Des Sioux in the extreme eastern portion of St. Charles county, Missouri was hard hit by microburst winds estimated at better than 70 mph. Several sheds and docks were destroyed. One man sustained injuries when airborne debris landed on him.
Figure 10: This is a location in east central Randolph county in Illinois. These photos were taken at a golf course near Percy, IL. Numerous twisted tree tops and the orientation of fallen trees and debris point to a tornado rather than straight line winds. The severity of the damage put this tornado in the F0/F1 category.
Figure 11: This is a location in east central Randolph county in Illinois. These photos were taken at a golf course near Percy, IL. Numerous twisted tree tops and the orientation of fallen trees and debris point to a tornado rather than straight line winds. The severity of the damage put this tornado in the F0/F1 category.
Figure 12: This is a location in east central Randolph county in Illinois. These photos were taken at a golf course near Percy, IL. Numerous twisted tree tops and the orientation of fallen trees and debris point to a tornado rather than straight line winds. The severity of the damage put this tornado in the F0/F1 category.
Figure 13: This is a location in east central Randolph county in Illinois. These photos were taken at a golf course near Percy, IL. Numerous twisted tree tops and the orientation of fallen trees and debris point to a tornado rather than straight line winds. The severity of the damage put this tornado in the F0/F1 category.

NWS
St. Louis, Missouri

Line of Severe Storms Moves Through the Bi-State Area
October 24th, 2001

Isolated thunderstorms that initially extended from Troy to Springfield, Missouri formed rapidly into a nearly solid line of severe thunderstorms before noon on October 24, 2001.  The severe storms formed along a progressive strong cold front which extended from northern Illinois to northern Oklahoma.  Unseasonably warm, moist, and unstable air from the south colliding with the colder air from the north, and strong winds aloft, combined to create a favorable setting for severe weather.  One storm which developed near Troy, Missouri at 1030 AM CDT (40 miles northwest of St. Louis - Lincoln county storm) took on the shape of a supercell (see reflectivity images below).  It produced hail and damaging winds over parts of Greene and Macoupin counties in southwest Illinois before exiting the St. Louis county warning area.  Strong rotation (a mesocyclone) near the pendant or hook-shaped echo are frequently observed with supercell storms.  Usually the largest hail and damaging winds occur in the southern part of the supercell, while tornadoes may occur in the vicinity of the hook.  The Lincoln county storm had a very long lifespan, and was traced over three hours, spawning tornadoes in east-central Illinois (northwest of Champaign, Illinois) and into northwest sections of Indiana.  Some supercells evolving in environments like October 24, 2001 will frequently have extended lifespans covering over 200 miles.  Other storms along the line became supercells as they moved into the St. Louis metro area after 1130 AM CDT.  Many of these storms were responsible for producing large hail and damaging winds across the metro area, including the damage at Portage Des Sioux.

After 215 PM CDT, a severe storm took on the shape of a bow echo over Perry county Missouri and traveled at speeds of 60 mph across southern and eastern Randolph county in Illinois.  A mesocyclone, showing strong rotation, was detected by the WFO St. Louis Doppler radar along the forward - northern side of the bowing segment.  Bow echoes are indicators of damaging winds and sometimes tornadoes form along the northern - forward side of the bow.  The mesocyclone with this bow echo spawned a weak tornado (F0 - F1) along the southern sections of Percy, Illinois after 230 PM CDT.

Over 55 reports of damaging winds and large hail were received at the NWS office in St. Louis on October 24th, making it one of the busiest severe weather days of 2001 across our area.

Map of Tornado Track in Percy, IL October 24th, 2001
Radar Picture from 1145 am on October 24th, 2001
Radar Picture from 1209 pm on October 24th, 2001

Radar Picture from 1230 pm on October 24th, 2001

 Radar Picture from 227 pm on October 24th, 2001

 Radar Picture from 227 pm on October 24th, 2001

 Storm Relative Motion from 227 pm on October 24th, 2001

 Damage at the Marina at Portage Des Sioux October 24th, 2001

 Damage at the Marina at Portage Des Sioux October 24th, 2001

 Damage Picture near Percy, IL October 24th, 2001

 Damage Picture near Percy, IL October 24th, 2001

 Damage Picture near Percy, IL October 24th, 2001

 Damage Picture near Percy, IL October 24th, 2001

     


Go back to the Event Archives


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.