NOAA's National Weather Service Weather Forecast Office

PRELIMINARY DAMAGE SURVEY FOR ST. CLAIR COUNTY INCLUDING THE COMMUNITY OF SHIOLH IN SOUTHWEST ILLINOIS.

National Weather Service personnel at St. Louis conducted a survey of the damage over parts of St. Clair county Illinois, southwest of the community of Shiloh.  A tornado initially touched down 2.5 miles southwest of the Shiloh Illinois in the Casa Verde subdivision and rapidly traveled northeast across the Whiteside Elementary School and a home for retired
priests. 

Thirty-four homes sustained varying degrees of damage with four homes having considerable damage. The overall damage showed a classic convergent damage pattern indicating signs of a tornado. Damage to homes in the subdivision was rated F1 with a damage width of 100 yards.  Immediately north of the newer subdivision, the first of two microburst occurred over an older part of the subdivision.  Several large trees were uprooted and showed a classic starburst type damage pattern. 

The tornado continued northeast and caused mainly roof damage to the Whiteside Elementary School and a home for retired priests.  The roof and side of a large home for retired priests sustained considerable damage.  Damage at the elementary school was rated F0 and at the home F1.  The damage width was 70 yards wide at both locations.
A second and more intense microburst occurred along the north side of the tornado track on the west side of the home for retired priests.  A classic divergent damage pattern was observed.

Only minor damage, mainly to the upper part of trees and shingles of homes were observed during the last one-half mile of the tornado track east of North Green Mountain Road.  The upper one-third part of a small radio tower over this area also sustained considerable damage. 

Damage path length: 1.75 miles
Damage path width: greatest 100 yards; average 75 yards.
Damage intensity:  F1

Photos taken in the Case Verde Subdivision 2 miles southwest of Shiloh Illinois.  Damage was rated F1 (73 - 112 mph) over this area.

(Top Images) Damage to the roof at the Whiteside Elementary School. (Bottom Images) Damage to the home for retired priest.  Classic convergent damage pattern was noted along the tornado path.  A classic divergent (starburst) pattern was noted with the two microbursts. (Photos - R. Przybylinski).

Sequence of plan view reflectivity / storm-relative velocity data at 0.5° slice from WSR-88D St. Louis (KLSX) for the period of 1030 - 1040 PM CDT.   A small bowing segment embedded with the larger convective line moved rapidly eastward across parts of St. Clair county Illinois.  The tornadic circulation formed along the northern forward side of a small bowing segment embedded within the larger squall line.  Circulations of this type often form at very low-levels then rapidly deepen and intensify.  The squall line was moving at speeds of 55 mph.  The tornado in this event is referred to as a 'non-supercell' tornado.

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