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Eleven tornadoes were confirmed across Illinois: seven in north central Illinois in the NWS Chicago County Warning Area (CWA), two in northwest Illinois in the NWS Quad Cities CWA, and two in central Illinois in the NWS Lincoln CWA.
Six of the tornadoes across north central Illinois formed from one supercell thunderstorm. This includes the strongest tornado that was a long track EF-4 with maximum winds of 200 mph. This tornado began from near Franklin Grove (Lee County), through the northwest side of Rochelle (Ogle County), across I-39, through Fairdale (DeKalb County), and ending south of Belvidere (far southern Boone County). This tornado caused two fatalities, both in Fairdale, and a total of 22 injuries.
A tornado of this magnitude is quite rare. This was the first EF-4 or stronger tornado in the NWS Chicago County Warning Area in 25 years, since an F5 tornado struck Plainfield on August 28, 1990. This was the strongest tornado on record (since 1950) for both Ogle and DeKalb Counties.
This was the first EF-4 tornado or stronger in Illinois since two EF-4 tornadoes occurred on November 17, 2013, including one that struck the community of Washington. This was the 33rd EF-4 or stronger tornado in Illinois on record (since 1950).
The atmosphere was ripe for severe weather due to highly anomalous moisture and instability for early April across the region. A strong low pressure system advanced into this favorable air mass. Combined with robust wind shear, this helped to trigger these potent storms.
The potential for severe weather was mentioned in NWS forecast graphics and products as early as Saturday, April 4th.
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PUBLIC INFORMATION STATEMENT...UPDATED
NATIONAL WEATHER SERVICE CHICAGO IL
1247 AM CDT WED APR 15 2015
...NWS DAMAGE SURVEY RESULTS FOR 04/09/15 TORNADO EVENT...
NWS METEOROLOGISTS HAVE NOW CONFIRMED SEVEN TORNADOES ACROSS
NORTH CENTRAL ILLINOIS FROM THE EVENING OF APRIL 9. NWS CHICAGO
WOULD LIKE TO EXPRESS APPRECIATION TO NASA SPORT FOR THE SATELLITE
IMAGERY...NOAA REMOTE SENSING DIVISION FOR THE HIGH RESOLUTION
AERIAL PHOTOGRAPHY...THE CIVIL AIR PATROL FOR AREAL
PHOTOGRAPHY...AS WELL AS THE ILLINOIS STATE POLICE AND THE MCHENRY
COUNTY EMERGENCY MANAGEMENT AGENCY FOR THEIR AERIAL DAMAGE PHOTOS
AS WELL. ALL OF THIS REMOTE SENSING DATA ALONG WITH THE GROUND
SURVEYS WERE INSTRUMENTAL IN IDENTIFYING THE TORNADO PATHS LISTED
BELOW AS WELL AS THE DAMAGE INTENSITY.
THE FIRST TORNADO WAS SPAWNED OVER FAR SOUTHEAST WINNEBAGO COUNTY
INTO BOONE COUNTY BY THE FIRST SUPERCELL THUNDERSTORM...WHILE THE
NEXT SIX TORNADOES FORMED FROM ONE POWERFUL AND LONG DURATION
SUPERCELL STORM...INCLUDING THE VIOLENT LONG TRACK EF-4 FROM
NORTHERN LEE COUNTY...THROUGH OGLE AND DEKALB COUNTIES...AND
ENDING IN FAR SOUTHERN BOONE COUNTY.
THE TORNADO COUNT FROM THE APRIL 9TH EVENT FOR THE NWS CHICAGO
COUNTY WARNING AREA STANDS AS FOLLOWS...
EF-4: 1
EF-1: 3
EF-0: 3
TORNADOES WERE ON THE GROUND FOR A TOTAL OF 43.5 MILES ACROSS
NORTH CENTRAL ILLINOIS.
HERE IS A LISTING OF THE CONFIRMED TORNADOES...
.TORNADO 1...
RATING: EF-0
ESTIMATED PEAK WIND: 65 MPH
PATH LENGTH /STATUTE/: 2.8 MILES
PATH WIDTH /MAXIMUM/: 25 YARDS
FATALITIES: 0
INJURIES: 0
START DATE: APRIL 09 2015
START TIME:6:37 PM CDT
START LOCATION: 2.9 MILES S CHERRY VALLEY
START LAT/LON: 42.1926/-88.9548
END DATE: APRIL 09 2015
END TIME:6:40 PM CDT
END LOCATION: 2.5 MILES SE CHERRY VALLEY
END_LAT/LON: 42.2174/-88.9106
AN EMERGENCY MANAGER AND TRAINED SPOTTERS PHOTOGRAPHED A
TORNADO THAT TOUCHED DOWN SOUTH OF CHERRY VALLEY. THE
TORNADO DID NOT PRODUCE ANY DAMAGE.
.TORNADO 2...
RATING: EF-4
ESTIMATED PEAK WIND: 200 MPH
PATH LENGTH /STATUTE/: 30.2 MILES
PATH WIDTH /MAXIMUM/: 700 YARDS
FATALITIES: 2
INJURIES: 22
START DATE:APRIL 09 2015
START TIME:6:39 PM CDT
START LOCATION:0.9 MILES NE FRANKLIN GROVE
START LAT/LON: 41.8530/-89.2896
END DATE:APRIL 09 2015
END TIME:7:20 PM CDT
END LOCATION:5 NNW KIRKLAND
END LAT/LON: 42.1623/-88.8792
THIS LONG TRACKED VIOLENT TORNADO DESTROYED NUMEROUS HOMES AND
FARMSTEADS...AS WELL AS TOSSED VEHICLES...ALONG ITS PATH FROM
NORTH CENTRAL LEE COUNTY ACROSS EASTERN OGLE...NORTHWEST
DEKALB...INTO EXTREME SOUTHERN BOONE COUNTY. THIS INCLUDED ACROSS
THE FAR NORTHWEST SIDE OF ROCHELLE...ACROSS INTERSTATE 39...AND
DIRECTLY THROUGH FAIRDALE.
| Path Segments of the EF-4 Tornado | ||||
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.TORNADO 3...
RATING: EF-0
ESTIMATED PEAK WIND: 65 MPH
PATH LENGTH /STATUTE/: 1.9 MILES
PATH WIDTH /MAXIMUM/: 100 YARDS
FATALITIES: 0
INJURIES: 0
START DATE:APRIL 09 2015
START TIME:7:05 PM CDT
START LOCATION:2.9 MILES E LINDENWOOD
START LAT/LON: 42.0583/-88.9752
END DATE:APRIL 09 2015
END TIME:7:08 PM CDT
END LOCATION:4.6 ENE LINDENWOOD
END LAT/LON: 42.0739/-88.9457
THIS BRIEF SATELLITE TORNADO OVER FAR EASTERN OGLE COUNTY WAS
CONFIRMED USING AERIAL SURVEY INFORMATION AND RADAR DATA.
.TORNADO 4...
RATING: EF-1
ESTIMATED PEAK WIND: 110 MPH
PATH LENGTH /STATUTE/: 4.0 MILES
PATH WIDTH /MAXIMUM/: 100 YARDS
FATALITIES: 0
INJURIES: 0
START DATE: APRIL 09 2015
START TIME: 7:15 PM CDT
START LOCATION: 3.1 MILES NW KIRKLAND
START LAT/LON: 42.1334/-88.8776
END DATE: APRIL 09 2015
END TIME: 7:21 PM CDT
END LOCATION: 6 MILES S BELVIDERE
END_LAT/LON: 42.1786/-88.8287
THIS TORNADO PATH WAS IDENTIFIED USING STORM CHASER VIDEO...GROUND
SURVEY AND AERIAL SURVEY INFORMATION. THE TORNADO FORMED IN FAR
NORTHWEST DEKALB COUNTY AND LIFTED IN FAR SOUTHERN BOONE COUNTY.
.TORNADO 5...
RATING: EF-0
ESTIMATED PEAK WIND: 85 MPH
PATH LENGTH /STATUTE/: 0.4 MILES
PATH WIDTH /MAXIMUM/: 30 YARDS
FATALITIES: 0
INJURIES: 0
START DATE: APRIL 09 2015
START TIME:7:24 PM CDT
START LOCATION: 3.8 MILES S BELVIDERE
START LAT/LON: 42.2073/-88.8425
END DATE: APRIL 09 2015
END TIME: 7:25 PM CDT
END LOCATION: 3.9 MILES S BELVIDERE
END_LAT/LON: 42.2020/-88.8465
THIS TORNADO WAS SPAWNED BY THE SAME STORM THAT PRODUCED THE LONG
TRACK EF-4 SHORTLY AFTER THAT TORNADO LIFTED.
.TORNADO 6...
RATING: EF-1
ESTIMATED PEAK WIND: 110 MPH
PATH LENGTH /STATUTE/: 3.9 MILES
PATH WIDTH /MAXIMUM/: 50 YARDS
FATALITIES: 0
INJURIES: 0
START DATE: APRIL 09 2015
START TIME:7:25 PM CDT
START LOCATION: 6 MILES SE BELVIDERE
START LAT/LON: 42.2442/-88.7386
END DATE: APRIL 09 2015
END TIME:7:31 PM CDT
END LOCATION: 5.6 MILES ESE BELVIDERE
END_LAT/LON: 42.1942/-88.7748
THIS TORNADO WAS SPAWNED BY THE SAME STORM THAT PRODUCED THE LONG
TRACK EF-4 SHORTLY AFTER THAT TORNADO LIFTED.
.TORNADO 7...
RATING: EF-1
ESTIMATED PEAK WIND: 90 MPH
PATH LENGTH /STATUTE/: 0.3 MILES
PATH WIDTH /MAXIMUM/: 30 YARDS
FATALITIES: 0
INJURIES: 0
START DATE: APRIL 09 2015
START TIME: 7:50 PM CDT
START LOCATION: 4.4 MILES EAST SOUTHEAST OF HARVARD
START LAT/LON: 42.3982/-88.5309
END DATE: APRIL 09 2015
END TIME:7:51 PM CDT
END LOCATION: 4.6 MILES EAST SOUTHEAST OF HARVARD
END_LAT/LON: 42.4019/-88.5272
THIS BRIEF TORNADO SNAPPED AND UPROOTED 6 TO 7 TREES AT A
PROPERTY ON MCGUIRE ROAD SOUTHEAST OF HARVARD THEN CAUSED MINOR
TREE DAMAGE ON THE NORTH SIDE OF THE ROAD BEFORE ENDING.
EF SCALE: THE ENHANCED FUJITA SCALE CLASSIFIES
TORNADOES INTO THE FOLLOWING CATEGORIES.
EF0...WEAK......65 TO 85 MPH
EF1...WEAK......86 TO 110 MPH
EF2...STRONG....111 TO 135 MPH
EF3...STRONG....136 TO 165 MPH
EF4...VIOLENT...166 TO 200 MPH
EF5...VIOLENT...>200 MPH
NOTE:
THE INFORMATION IN THIS STATEMENT IS PRELIMINARY AND SUBJECT TO
CHANGE PENDING FINAL REVIEW OF THE EVENT AND PUBLICATION IN
NWS STORM DATA.
$$
NWS CHICAGO
Aerial Damage Photos
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| Landsat-8 Satellite image clearly showing the track of the tornado (Darkened line area northwest of Rochelle, IL) |
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| Northwest Rochelle Tornado Damage (Courtesy Civil Air Patrol) | Northwest Rochelle Tornado Damage (Courtesy Civil Air Patrol) |
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| Another view of damage to a neighborhood northwest of Rochelle showing high-end EF-4 impacts to homes. (Courtesy Air-One and photographer Dave Youngblut) |
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| Fairdale (Courtesy Civil Air Patrol) | Aerial of Fairdale looking Northeast. Courtesy of NGS/NOAA |
Ground Damage Photos
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| Northwest Side of Rochelle | North of Rochelle |
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| Fairdale Area |
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| Fairdale Area | Fairdale Area |
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NWS Chicago Facebook April 9, 2015 Photo Album
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| East of Dixon. This is the base of the storm that would soon thereafter produce the long-lived tornado that would track into Ogle and DeKalb Counties. Courtesy of Lora Ludwig. |
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| Near Ashton. Courtesy of PBrooks Photography. |
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Looking northwest of Rochelle. Courtesy of Dean Schultz. |
Large hail at McHenry Country Club. Courtesy of Jeff Grubich. |
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| Near I-39 Looking North of Rochelle. Courtesy of Jodi Mair. |
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| Near I-39. Courtesy of Walker Ashley. |
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| Near Hillcrest. Courtesy of Larissa Sebree. |
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| Radar loop from 3:30 pm - 8:45 pm on April 9, 2015 |
The four panel radar images below display: radar reflectivity (top left), radar storm relative velocities from two different radars (top right and bottom right) and Correlation Coefficient (CC). Storm relative velocity tells us if a storm has rotation. The green colors in the imagery represent winds blowing towards the radar, while the red colors indicate winds blowing away from the radar. Therefore, strong rotation can be inferred in the storms showing bright red colors directly adjacent to bright green colors in the storm relative velocity images. This is also the area of the storm where the tornado is most likely to be occurring. Reflectivity and storm relative velocity used together with CC data can indicate the presence of debris resulting from a tornado. In basic terms CC is the correlation between the reflected horizontal and vertical power returns that the dual pol weather radar provides. CC data tends to be near one with most precipitation type echoes. Therefore, when the CC data is found to be very low (represented by the blue colors), it suggests that the radar is not sampling precipitation.
Notice that in the second radar four panel for the Franklin Grove to Margeno supercell time stamped 6:59 pm that a clear area of low CC data (Blue area) is identifiable within the radar reflective hook echo just north of Rochelle. This area also corresponds with the area of strong rotation as noticed in the storm relative velocity image in the top right. The Low CC in this area tells the radar operator that the strong reflectiveives within the hook echo in the top left panel is not precipitation, but is actually the radar seeing the debris being lofted from a tornado.
| Near Rockford Airport to Cherry Valley to Harvard Supercell | |
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| 6:37 pm | 6:52 pm |
| Franklin Grove to Fairdale to Belvidere to Margeno Supercell | |
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| 6:45 pm | 6:59 pm |
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| 7:15 pm | 7:29 pm |
The atmosphere was ripe for severe weather due to highly anomalous moisture and instability for early April across the region. A strong low pressure system advanced into this favorable air mass. Combined with robust wind shear, this helped to trigger these potent storms.
| NWS Storm Prediction Center Severe Weather Outlooks for April 9th and Dates Issued | ||||
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| April 4th | April 5th | April 6th | April 7th | April 8th |
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| Day 1 Severe Weather Outlook Issued on April 9th at 11:30 a.m. | Day 1 Tornado Outlook Issued on April 9th at 11:30 a.m. |
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| Tornado Watch Issued at 1:50 pm | Graphical Short Term Forecast at 6:10 pm | Graphical Short Term Forecast at 7:40 pm | NWS Warnings on April 9th from 12pm-12am |
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