Northern Illinois is beginning to grow accustomed to strange out of season tornadoes. On January 7th, 2008, an EF-3 tornado with wind speeds as high as 160 mph ripped through Boone and McHenry Counties. Then, on November 22nd, another strange out of season tornado touched down, in nearly the same place. Had it touched down earlier, however, we may have had an entirely different situation on our hands.
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| 11/22 tornadic supercell with visible BWER (bounded weak echo region, area of lower reflectivity sw of Loves Park and nw of Rockford) associated with the storm's updraft, and sometimes a precursor to tornadogenisis. |
These radar images (Storm Relative Velocity) depict the motion of particles within the storm. The doppler radar is able to detect this the same way as a police radar detects the speed of a vehicle. Meteorologists are able to use this product to detect rotation within thunderstorms, and sometimes detect tornadoes.
This is the SRV at 2:51 pm. Although the radar is picking up some rotation just northwest of downtown Rockford, there is no tornado warning, possibly because the rotation isn't quite strong enough to validate a warning at the time. HOWEVER:
Seen here is the same storm, but viewed at a higher elevation, ten minutes earlier (2:41 pm). There is very strong rotation at around 13kft, just southeast of Winnebago.
Here you can clearly see the meso tighten up. This is at about 6,500 ft. The velocity couplet is now exhibiting strong maxed out velocities in both directions. This image is at about 2:56 pm, four minutes before the tornado warning was issued.
At 3:00 pm, the NWS Chicago issued a tornado warning for Winnebago, Boone, and McHenry counties...
THE NATIONAL WEATHER SERVICE IN CHICAGO HAS ISSUED A* TORNADO WARNING FOR...
NORTHERN BOONE COUNTY...
NORTHWESTERN MCHENRY COUNTY...
EAST CENTRAL WINNEBAGO COUNTY...
* UNTIL 330 PM CST
* AT 300 PM...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO. THIS DANGEROUS
STORM WAS LOCATED NEAR LOVES PARK...AND MOVING NORTHEAST AT 50 MPH.
* LOCATIONS IMPACTED INCLUDE...
HARVARD...POPLAR GROVE AND CAPRON.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
TAKE COVER NOW. MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF A
STURDY BUILDING. AVOID WINDOWS. IF IN A MOBILE HOME...A VEHICLE OR
OUTDOORS...MOVE TO THE CLOSEST SUBSTANTIAL SHELTER AND PROTECT
YOURSELF FROM FLYING DEBRIS.
&&
LAT...LON 4249 8856 4240 8846 4222 8895 4238 8909
4250 8888
TIME...MOT...LOC 2103Z 237DEG 42KT 4236 8892
Unfortunately, judging by radar images, this warning was only issued about a minute or possibly less before the tornado was on the ground.
This image shows the tight circulation crossing I-39/90 at 3:00, when the first tornado warning was issued. The tornado touched down right around this area.
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| Tornado path very distinct just after I-39/90 (center of image) near Rock Cut State Park (right) |
Here the velocity couplet is shown entering Caledonia. Most of the most devastating damage done by this storm was in the Caledonia area, where the tornado's winds were likely reaching up to around 135 mph or more.
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| Image as tornado moves away from Caledonia at 3:09 pm. |
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| Tree damage at Beloit Rd. |
All in all, Rockford and surrounding areas lucked out big time on this one. If this tornado would have touched down even 5 minutes earlier, it likely would have ripped through parts of Rockford and Loves Park. Ten minutes earlier, and it would have ripped nearly right across town. The damage would have been far worse, being more structures "strengthen" the tornado in a way, giving it more power by turning it into a massive "blender". Not to mention, it would have moved through a much more heavily populated area.
Although the tornado did do quite a bit of damage in Boone and McHenry counties, luckily nobody was seriously injured. This storm also went on to produce an EF-1 tornado just over the state line.
Donovan Gruner
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