Friday, July 10, 2015   |   Case Studies

June 22, 2015: Coal City EF-3 Tornado

A very large, high-precipitation supercell moved across the full width of Illinois on the evening of Monday, June 22. In all, 12 separate tornadoes were confirmed by the U.S. National Weather Service, but one in particular, an EF-3 tornado that hit the town of Coal City, Ill. just before 10 pm, caused extensive damage with winds up to 160 mph.

This post-event case study analyzes the formation and path of the tornado, as well as the performance of Baron value-added data products and automated weather alerting during the event.


6_22_cc_857_ref_shear_box8:57 pm

About 45 minutes before the largest tornado strikes the Coal City area, the supercell is producing wind damage and intermittent weaker tornadoes along its destructive path. At 8:57 pm, numerous Baron Shear Markers are triggered by the storm, with a Baron Shear SCIT pointing in the direction of Coal City.


9:23 pm

A look at a 1-hour Shear Rate mosaic at 9:23 pm clearly shows the path of the highest wind shear as the storm approaches the town.




9:26 pm

At 9:26 pm, 115 mph of shear is detected as the storm nears Coal City. Baron Shear Markers continue to trigger over the most dangerous part of the storm, as a Baron Shear SCIT points in the direction of Coal City.



saftnetbox_19:30 pm

At 9:28 pm, the National Weather Service issues a Tornado Warning (red, below) that includes Coal City. This warning is based on radar-indicated rotation.

About 20 minutes before the tornado hits the town, at 9:39 pm, a Baron Safety Net alert for twisting storms is automatically generated for the specific area of Coal City. Baron alert types are shown as blue boxes in the image above.


9:45 pm

The National Weather Service updates the issued Tornado Warning with spotter confirmation of a funnel on the ground.


6_22_cc_955_ref_shear_box9:55 pm

By 9:55 pm, the supercell thunderstorm is moving through and just south of Coal City, Illinois. The tornado is currently on the ground. 6_22_cc_955_velocity




During this time, Baron De-aliased Level II Velocity data shows a very tight and intense couplet. Strong outbound returns (red) are visible next to strong inbound returns (green), indicating a likely tornado immediately south of Coal City.



9:58 pm

The Baron Button, an exclusive value-added product, indicates 100 mph of rotation at the area corresponding to the strong velocity couplet.




10:00 pm

By 10:00 pm, the storm has moved further southeast, to the south of Coal City. Baron-derived Shear Rate shows the location of the highest amount of shear.




In the same location at the same time, an area of low Correlation Coefficient (RHO) is evident, indicating a likely area of debris thrown aloft by the tornado.





10:05 pm

On the next scan at 10:05 pm, a Baron TDS (Tornado Debris Signature) marker is present, a further indication of debris aloft.




10:21 pm

Looking at a 1-hour mosaic of Shear Rate, it is easy to determine the location and movement of the most dangerous part of the high-precipitation supercell, and also that the storm was at its strongest as it moved through the Coal City area.



This image shows a local storm report with confirmation of the tornado, along with Baron and NWS alert boxes.










Lastly, this image shows all alerts issued over a 3-hour period, clearly tracing the path of the storm.










Broadcast customers subscribing to Data Essentials receive Baron SCITs. Other value-added data like Baron Shear Markers, TDS Indicator, Baron Button and others are available to Data Innovations subscribers.