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ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-131300-

Public Information Statement
National Weather Service Chicago IL
747 PM CDT Wed Aug 12 2020 /847 PM EDT Wed Aug 12 2020/

...NWS DAMAGE SURVEY FOR 08/10/2020 DERECHO AND TORNADO EVENT...

.UPDATE...
Through a combination of storm surveys, photos, video, and
coordination with area EMAs, four additional tornado paths have 
been identified in association with the 08/10/2020 Derecho. These 
are: an EF-0 in Grant Park, and EF-0 in Park Forest, an EF-1 
between Yorkville and Plainfield, and an EF-1 in Ottawa. This 
brings the total number of tornadoes in NWS Chicago's area of 
responsibility to 11 from the 8/10/2020 Derecho event. In 
addition, information about significant straight line winds in 
Forreston (NW Ogle County), Somonauk ((Dekalb and LaSalle
Counties) and a corridor of enhanced straight line wind damage 
between Wheaton and Glen Ellyn (DuPage County) have been added. 

NWS Chicago continues to work with our local partners to diagnose
potential additional areas of tornado damage. We hope to have this
information finalized on Thursday. 

.OVERVIEW...
A well-organized and long-lived thunderstorm complex produced 
widespread severe wind damage across northern Illinois and Indiana
during the afternoon hours on Monday, August 10th. Associated 
straight line wind damage across NWS Chicago’s area of 
responsibility is consistent with 60 to 80 mph wind gusts, with 
pockets of enhanced winds likely in excess of 90 mph. 

Several tornadic circulations developed within the main line of 
thunderstorms, producing at least nine tornadoes across northern 
ILlinois. In addition, a lone supercell that was subsequently 
absorbed into the main line produced two tornadoes in and around 
the Rockford area, bringing the event total tornadoes to at least 
eleven. 


.FORRESTON AREA STRAIGHT LINE WINDS...

Estimated peak wind:    100 mph
Fatalities:             0
Injuries:               5

Start date:             08/10/2020
Start time:             2:15 PM CDT
Start location:         Forreston

End date:               08/10/2020
End time:               2:30 PM CDT
End location:           Forreston

Very strong straight line winds of 90 to 100 mph occurred in the
town of Forreston in far northwestern Ogle County. Reports
indicate that several mobile homes on the east side of the town
were damaged or destroyed, and photos also revealed significant
damage to a metal building near the BP gas station with associated
debris all blown towards the northeast. Widespread tree damage
also occurred. 


.SOUTHWEST ROCKFORD TORNADO...

Rating:                 EF-0
Estimated peak wind:    75 mph
Path length /Statute/:  1.5 miles
Path width /Maximum/:   50 yards
Fatalities:             0
Injuries:               0

Start date:             08/10/2020
Start time:             2:37 PM CDT
Start location:         3 SW Rockford

End date:               08/10/2020
End time:               2:38 PM CDT
End location:           1.5 SW Rockford

Survey Summary:
A very brief tornado touched down near the intersection of
Pierpont Ave and Montague Road and continued northeast into the
southwest side of Rockford. The tornado ended near the
intersection of Ferguson and Loomis streets.  All damage was to 
trees along the tornado path. 


.ROCKFORD TO CALEDONIA TORNADO...

Rating:                 EF-1
Estimated peak wind:    100 mph
Path length /Statute/:  9.2 miles
Path width /Maximum/:   300 yards
Fatalities:             0
Injuries:               0

Start date:             08/10/2020
Start time:             2:47 PM CDT
Start location:         3 NE Rockford

End date:               08/10/2020
End time:               3:05 PM CDT
End location:           1 SW Caledonia 

Survey Summary:
This tornado was associated with the same supercell thunderstorm
that produced an initial brief EF-0 tornado immediately southwest
of Rockford, but it has been determined these exist as two
separate tracks. This tornado developed as the main line of
thunderstorm caught up, and eventually merged with, the parent 
supercell with this path starting near Guilford Road just north of
Rockford College before heading northeast. Significant tree 
damage, consistent with EF-1 wind speeds, occurred in a localized 
area immediately east of Rock Valley College west of North 
Perryville Road. The tornado continued northeast, crossing 
I-90/39, producing sporadic damage before lifting near Caledonia 
Road. 


.OTTAWA TORNADO...

Rating:                 EF-1
Estimated peak wind:    100 mph
Path length /Statute/:  0.75 miles
Path width /Maximum/:   150 yards
Fatalities:             0
Injuries:               0

Start date:             08/10/2020
Start time:             2:59 PM CDT
Start location:         Ottawa

End date:               08/10/2020
End time:               3:01 PM CDT
End location:           Ottawa

The tornado started south of Marquette street west of Michigan
street and progressed eastward. The tornado impacted several
businesses ripping off well-anchored roofing material and snapping
a power pole at its base. It was here that the max intensity of
the tornado was reached with peak winds of around 100 mph. The
tornado then continued eastward ripping shingles off roofs of
buildings and houses just west of Route 23 and shredding trees.
The tornado is believed to have lifted in an inaccessible forested
area east of the Fox river. Eye witnesses indicated the tornado
may have had multiple vortices with clear rising and rotating
motion of debris. 


.SOMONAUK STRAIGHT LINE WINDS...

Estimated peak wind:    90 mph
Fatalities:             0
Injuries:               0

Start date:             08/10/2020
Start time:             2:59 PM CDT
Start location:         Somonauk

End date:               08/10/2020
End time:               3:01 PM CDT
End location:           Somonauk

Widespread tree damage with a few trees snapped very near their
base were observed throughout Somonauk and surrounding areas.
Seven large and new utility poles were also snapped about 10 feet
up from thier base about three miles north of Somonauk on 
Somonauk Road. The damage was consistent with straight line winds 
up to 90 mph. 


.SOUTHEAST MARENGO TORNADO...

Rating:                 EF-1
Estimated peak wind:    95 mph
Path length /Statute/:  5.7 miles
Path width /Maximum/:   200 yards
Fatalities:             0
Injuries:               0

Start date:             08/10/2020
Start time:             3:05 PM CDT
Start location:         5 SW Marengo

End date:               08/10/2020
End time:               3:11 PM CDT
End location:           3 SW Marengo 

Survey Summary:
This EF-1 tornado started on Harmony Road immediately southwest of
I-90 near the McHenry/DeKalb County line. Tree damage consistent
with winds around 95 mph occurred immediately northeast of I-90.
The tornado heavily damaged a single family home near Maple Street
before heading northeast and lifting near Coral and Dunham Roads.


.YORKVILLE TO SOUTH PLAINFIELD TORNADO...  

Rating:                 EF-1
Estimated peak wind:    105 mph
Path length /Statute/:  14.5 miles
Path width /Maximum/:   250 yards
Fatalities:             0
Injuries:               0

Start date:             08/10/2020
Start time:             3:15 PM CDT
Start location:         4 S Yorkville

End date:               08/10/2020
End time:               3:30 PM CDT
End location:           4 S Plainfield

The tornado started on the far south side of Yorkville near Walsh
Drive where a pergola was destroyed, siding was ripped off a
house, and parts of a fence and a tree were thrown over a roadway.
Eyewitnesses accounts indicate the debris was lifted and twirled,
consistent with a tornado. The tornado then progressed east- 
southeastward producing damage to trees along State Route 126 
toward Schlapp Road. The most significant damage was found east of
Schlapp Road along Wheeler road where trees were mangled, a farm 
building was destroyed with debris deposited in a nearby field, 
and a large grain bin was bent inward. Wood panels were thrown 
into the ground leaving scour marks in the grass. Six power poles 
were snapped along Ridge road, and a 1000-1500 lb auger was moved 
about 50 feet. This is where the tornado likely reached peak 
intensity with winds near 105 mph. The tornado continued southeast
into neighborhoods south of Renwick road producing mainly tree 
damage, and ended just before I-55. A swath of damaging winds 
consistent with speeds of 70 to 80 mph continued into Crest Hill 
based on prolific tree damage. 


.WHEATON TORNADO....

Rating:                 EF-1
Estimated peak wind:    90 mph
Path length /Statute/:  0.3 miles
Path width /Maximum/:   200 yards
Fatalities:             0
Injuries:               0

Start date:             08/10/2020
Start time:             3:35 PM CDT
Start location:         .25 NE Wheaton

End date:               08/10/2020
End time:               3:36 PM CDT
End location:           0.5 NE Wheaton

Survey Summary:
A very brief tornado touched down near the intersection of
Seminary Avenue and Scott Street before moving northeast where it
knocked a roughly 50 foot steeple around to the north side of the
College Church in Wheaton. The tornado then produced minor tree
damage before  lifting near College Avenue and Howard Street. 


.WHEATON TO GLEN ELLYN STRAIGHT LINE WINDS...

Estimated peak wind:    90 mph
Fatalities:             0
Injuries:               0

Start date:             08/10/2020
Start time:             3:36 PM CDT
Start location:         1 ENE Wheaton

End date:               08/10/2020
End time:               3:38 PM CDT
End location:           1 NE Glen Ellyn

After a very brief break in damage after the Wheaton tornado
lifted, a corridor of enhanced straight line winds developed at
the southern flank of a circulation. Damage to trees and utility
poles were noted, with the peak of the damage corridor occurring
east of North Main Street and towards Lake Ellyn Park. Damage in
this region is consistent with wind speeds of up to 90 mph. 


.LOMBARD/VILLA PARK TORNADO....

Rating:                 EF-1
Estimated peak wind:    95 mph
Path length /Statute/:  2.1 miles
Path width /Maximum/:   200 yards
Fatalities:             0
Injuries:               0

Start date:             08/10/2020
Start time:             3:39 PM CDT
Start location:         1 NE Lombard

End date:               08/10/2020
End time:               3:42 PM CDT
End location:           1 NW Villa Park

Survey Summary:
The same storm which produced the brief Wheaton tornado produced
another region of tornado damage immediately east of I-355 just
east of Lilacia Park. This tornado also continued in a
northeasterly direction, uprooting trees--some snapped at the
trunk--as well as causing some house damage including a few with
substantial roof damage. The worst damage occurred near and around
the Lombard Common just south of St. Charles Road. Damage eased
considerably on the north side of the circulation, with a more
gradual drop off in damage to its south. The tornado lifted just 
northeast of the Jefferson Middle School. 


.PARK FOREST TORNADO...

Rating:                 EF-0
Estimated peak wind:    85 mph
Path length /Statute/:  2 miles
Path width /Maximum/:   350 yards
Fatalities:             0
Injuries:               0

Start date:             08/10/2020
Start time:             3:57 PM CDT
Start location:         1.5 SW Park Forest

End date:               08/10/2020
End time:               4:59 PM CDT
End location:           0.5 ESE Park Forest

A brief tornado touched down very close to the Cook/Will county
line near Shabbona Drive. It racked northeast where it produced a
localized area of fairly widespread tree damage consistent with
high-end EF-0 wind speeds. The worst damage was confined to a
small area near Marquette and Somonauk Parks, although very little
structural damage was noted in this area. The tornado lifted over
Schuberts Woods Forest Preserve. Sporadic straight-line wind
damage continued east towards State Street east of South Chicago
Heights. 


.ROGERS PARK (CHICAGO) TORNADO....

Rating:                 EF-1
Estimated peak wind:    110 mph
Path length /Statute/:  3.2 miles
Path width /Maximum/:   300 yards
Fatalities:             0
Injuries:               0

Start date:             08/10/2020
Start time:             3:59 PM CDT
Start location:         Near Lincolnwood

End date:               08/10/2020
End time:               4:04 PM CDT
End location:           Jarvis and Fargo Beaches

Survey Summary:
This tornado initially touched down south of the intersection of
Crawford and Touhy avenues in the suburb of Lincolnwood. It then
continued moving just north of due east before moving offshore
near the Jarvis and Fargo Beaches. The most intense damage,
consistent with that of a high-end EF-1 tornado, occurred within 
approximately one mile of the lakefront, as well as near and 
within Phillip Rogers Park.


.GRANT PARK TORNADO...

Rating:                 EF-0
Estimated peak wind:    80 mph
Path length /Statute/:  1.5 miles
Path width /Maximum/:   250 yards
Fatalities:             0
Injuries:               0

Start date:             08/10/2020
Start time:             4:04 PM CDT
Start location:         1 NE Grant Park

End date:               08/10/2020
End time:               4:06 PM CDT
End location:           Grant Park

An EF-0 tornado touched down just northwest of Grant Park along N
11000 E Road and traveled southeast through Grant Park.
Considerable tree damage was found along the path. The tornado
ended near Lake Metonga. 


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. 

We thank local academic and emergency management partners for
their help in surveying the damage from the 8/10/2020 derecho
event. 

$$

Bardou/Borchardt/Carlaw/Castro/Izzi/Lenning/Lincoln/Sirvatka