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Marissa Illinois Tornado and Damaging Wind Event - August 19, 2004 |
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| During the late afternoon of August 19, 2004 discrete convective storms developed over northern Randolph County Illinois and moved east-northeast into far southeast St. Clair county. One of the stronger storms spawned a weak tornado 4.0 miles north-northeast of Marissa and caused minor structural and tree damage beginning 1.0 mile southwest of the intersection of Lenzburg East Road and Illinois Highway 4. Two microbursts were identified during the assessment, one adjacent and southeast of the tornado track and a second approximately 1.0 mile south of the tornado track. Tree and corn damage were noted with each of the microbursts. The overall width of the tornadic damage track was approximately 40 yards while the overall damage length was 2.0 miles. | ||
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Damage to two machine sheds near the southwest corner of Lenzburg East Road and Illinois Highway 4 in far southeast St. Clair County. Windows and sliding from a nearby farm home (immediately left of the picture) were damaged. Witnesses at this farmstead and adjacent farmstead observed the tornado and described it having a mikly white appearance. Viewing southwest. Click on image for a larger view of this picture. | |
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Debris from the machine sheds was scattered north of Lenzburg East Road and west of Highway 4. Viewing north-northwest. | |
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In addition to the scattered debris a few large trees were snapped near the base of the trunk. Viewing east-northeast. | |
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Scattered tree damage north of Lenzburg East Road and immediately west of Highway 4. Viewing northeast. | |
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Approximately 3/4 mile northeast of the intersection of Lenzburg East Road and Highway 4, several trees were snapped halfway up in a wooded area. Viewing northeast. | |
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A microburst partially or completely flattened corn along and south of the tornado track east of Highway 4 and along and north of Erb Road. | |
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Far left image: Low-level plan-view reflectivity image from WFO St. Louis at 4:42 PM CDT showing the discrete mini-supercell which spawned the weak tornado and caused wind damage south of the tornado track. Near left image: shows the low-level storm-relative velocity image of a weak mesovortex just prior to tornado touchdown. The mesovortex is located near the northwest side of the discrete storm. |
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Far left image: Low-level plan-view reflectivity image taken at 4:52 PM CDT from WFO St. Louis. The discrete mini-supercell moved into far southwest Washington County Illinois. Near left image: Low-level plan-view storm-relative velocity image showing a second mesovortex with this storm. This mesovortex was responsible for producing wind damage. |
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