Alert archive / Illinois / Severe Thunderstorm Warnings in 2003

Severe Thunderstorm Warning 142, NWS Chicago, IL

July 20, 2003Cook County, Illinois

NWS Chicago, IL issued this severe thunderstorm warning at Jul 20, 2003, 10:50 PM CDT for Cook County, Illinois. It was in force for 25 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Jul 20, 2003, 10:50 PM CDT (03:50 UTC)
Expired: Jul 20, 2003, 11:15 PM CDT
In force: 25 min
Issued by: NWS Chicago, IL
Area: Counties, with a storm outline in the text

County Cook County, IL

The radar

The Chicago radar (KLOT), 49 km from the middle of the area, began a volume at 03:53 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

Did it verify

Not verified. The Iowa Environmental Mesonet's Cow found no qualifying storm report inside this severe thunderstorm warning while it was in force. That is not proof nothing happened: reports are thin where few people live.

Cow counts a report within 15 km of the polygon while the warning was in force: a tornado for a tornado warning; hail of 1 inch or more, a gust of 58 mph or more or wind damage for a severe thunderstorm warning; a flash flood report for a flash flood warning.

The watch it was issued in

The SPC watch in force over the same counties when this warning went out.

Issued	Product	Office	Lasted
Jul 20, 10:15 PM CDT	Severe Thunderstorm Watch	SPC	7 hr

The nearest sounding before it

Lincoln, IL (KILX), launched 00:00Z, 3.8 hours before the alert went out and 210 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 3794 J/kg
Mixed-layer CIN: -5 J/kg
Mixed-layer LCL: 1094 m above ground
0-6 km bulk shear: 39 kt
0-1 km storm-relative helicity: 10 m²/s²
0-3 km storm-relative helicity: 40 m²/s²
Significant tornado parameter: 0.4
Supercell composite: 2.8

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Chicago, IL wrote its last area forecast discussion before this severe thunderstorm warning went out at Jul 20, 3:15 PM CDT, 7 hours 35 minutes earlier.

Area forecast discussion, Jul 20, 3:15 PM CDT, 7 hours 35 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO IL
315 PM CDT SUN JUL 20 2003

PUBLIC DISCUSSION AFTERNOON ZONES/GRIDS:

MAIN PROBLEM THIS EVENING IS WITH TSTM FCST.  SPC HAS LOWERED REGION
INTO SLIGHT RISK AS LO LEVEL FEATURES ARE AS YET POORLY DEFINED. SFC
DEW POINTS HAVE RISEN INTO LOER 70S BUT MOISTURE CONVERGENCE REMAINS
QUITE NEBULOUS ACROSS MOST OF MIDWEST.  CONVECTIVE DEBRIS HAS
CONTRIBUTED TO RELATIVE STABILIZATION COMPARED TO AREAS TO OUR W AND
S WHERE LIFTED INDEX VALUES ARE NOW RUNNING AOB -10.  BASED ON
THIS...BELIEVE DYNAMIC FORCING WILL BE REQUIRED TO GENERATE
CONVECTION.  VIGOROUS, DIGGING S/W TROF NOW ROTG SSEWD ACROSS WRN
ONTARIO WITH VORT TAIL ARCING SWWD INTO ND ATTM BASED ON AFTN SATLT
LOOPS.  EXPECT THIS TO TRIGGER MORE ORGANIZED CONVECTION NXT FEW HRS
WELL TO OUR NW WITH THESE STORMS MAINTAINING THEMSELVES OVERNIGHT
DUE TO MORE FAVORABLE DYNAMICS.  AS A RESULT WILL KEEP LIKELY POPS
GOING IN FCST BUT WILL MENTION THIS AS AN OVERNIGHT EVENT.  THIS IS
ALSO SUPPORTED BY MOS AND ALL MODELS CONCUR IN BRINGING OMEGA MAX
ACROSS FA OVERNIGHT.  SOME PRECIP WILL LIKELY LINGER INTO MONDAY
MORNING.  REMAINDER OF FCST CHANGED LTL FROM GUID WITH ETA AND GFS
IN FAIRLY GOOD AGREEMENT ON STRENGTH OF COLD AVDECTION THRU ERLY
PART OF UPCOMING WEEK.   WILL KEEP MOSTLY CLOUDY CONDS AT LEAST THRU
MONDAY DUE TO SHARP CYCLONINC TURNING IN MID/UPR LVL FLOW AND ASSD
COLD ADVECTION.  SKIES SHOULD CLEAR TUES NIGHT AS H5 TROF AXIS
SHIFTS EWD AND SFC HI PRES BUILDS SEWD INTO FA.

.CHI...NONE
MERZLOCK

Hazardous weather outlook, Jul 20, 7:35 PM CDT, 3 hours 15 minutes before

ILZ003>006-008-010>014-019-020>023-032-033-039-INZ001-002-010-011-019
-2011200-

HAZARDOUS WEATHER OUTLOOK/UPDATED
NATIONAL WEATHER SERVICE CHICAGO IL
735 PM CDT SUN JUL 20 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL AND NORTHEAST
ILLINOIS...NORTHWEST INDIANA...AND THE ADJACENT WATERS OF LAKE
MICHIGAN.

.DAY ONE...TONIGHT

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE TONIGHT OVER
NORTHERN ILLINOIS AND NORTHWEST INDIANA.

A STRONG COLD FRONT AND UPPER AIR DISTURBANCE ARE STILL TO THE
NORTHWEST OF ILLINOIS. THUNDERSTORMS MAY REDEVELOPE TOWARD MIDNIGHT
OVER SOUTHWEST WISCONSIN AND THEN MOVE SOUTHEAST OVER THE AREA. ANY
STORMS WILL BE CAPABLE OF HIGH WINDS AND HAIL.

.DAYS TWO THROUGH SEVEN... MONDAY THROUGH SUNDAY

THERE IS A CHANCE OF LINGERING SHOWERS AND THUNDERSTORMS EARLY
MONDAY. THESE THUNDERSTORMS ARE NOT EXPECTED TO BE SEVERE.  THE NEXT
CHANCE OF THUNDERSTORMS WILL BE ABOUT SATURDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED AGAIN LATE TONIGHT.
.

&&

           NWS CHICAGO WEBPAGE

    HTTP://WWW.CRH.NOAA.GOV/LOT (LOWER CASE)
OR  HTTP://WEATHER.NOAA.GOV/CHICAGO (LOWER CASE)

AF

In the hours before

Local storm report, Jul 20, 6:09 PM CDT, 4 hours 41 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO IL
609 PM CDT SUN JUL 20 2003

TIME(CDT)  .....CITY LOCATION..... STATE  ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0608 PM    HOMETOWN                  IL   WIND DAMAGE
07/20/03   COOK                           WIND GUST TO 60 MPH
                                          WITH MODERATE TREE
                                          LIMBS DOWN. REPORTED BY
                                          STORM SPOTTER.

Local storm report, Jul 20, 6:21 PM CDT, 4 hours 29 minutes before

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Local storm report, Jul 20, 6:58 PM CDT, 3 hours 52 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO IL
658 PM CDT SUN JUL 20 2003

TIME(CDT)  .....CITY LOCATION..... STATE  ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0604 PM    BURBANK                   IL   60 MPH TSTM GUST
07/20/03   COOK                           REPORTED BY HAM RADIO
                                          OPERATOR.

0608 PM    HOMETOWN                  IL   WIND DAMAGE
07/20/03   COOK                           WIND GUST TO 60 MPH
                                          WITH MODERATE TREE
                                          LIMBS DOWN. REPORTED BY
                                          STORM SPOTTER.

0612 PM    EVERGREEN PARK            IL   WIND DAMAGE
07/20/03   COOK                           A FEW TREES DOWN. ONE
                                          TREE UPROOTED AND FELL
                                          ONTO HOUSE. REPORTED BY
                                          MEDIA.

0615 PM    WOODRIDGE                 IL   WIND DAMAGE
07/20/03   DUPAGE                         WIND GUSTS 50-60 MPH
                                          WITH LIMBS DOWN ON
                                          BRENTWOOD CT. REPORTED
                                          BY LAW ENFORCEMENT
                                          OFFICIAL.

Special weather statement, Jul 20, 7:15 PM CDT, 3 hours 35 minutes before

ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-
ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-ILZ023-ILZ032-ILZ033-ILZ039-
210200-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE CHICAGO IL
715 PM CDT SUN JUL 20 2003

THE NATIONAL WEATHER SERVICE IN CHICAGO HAS CLEARED ALL COUNTIES
IN SEVERE THUNDERSTORM WATCH 774. COUNTIES CLEARED INCLUDE:

IN ILLINOIS:
BOONE...COOK...DE KALB...DU PAGE...FORD...GRUNDY...IROQUOIS...
KANE...KANKAKEE...KENDALL...LAKE...LA SALLE...LEE...LIVINGSTON...
MCHENRY...OGLE...WILL...WINNEBAGO...

THIS INCLUDES THE CITIES OF...AURORA...BELVIDERE...CHICAGO...
DE KALB...DIXON...GIBSON CITY...JOLIET...KANKAKEE...LA SALLE...
MORRIS...NAPERVILLE...OREGON...PONTIAC...ROCKFORD...WATSEKA...
WAUKEGAN...WOODSTOCK...YORKVILLE...

Local storm report, Jul 20, 10:39 PM CDT, 11 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO IL
1039 PM CDT SUN JUL 20 2003

TIME(CDT)  .....CITY LOCATION..... STATE  ...EVENT/REMARKS...
           ....COUNTY LOCATION....

1034 PM    KANKAKEE                  IL   1.75 INCH HAIL
07/20/03   KANKAKEE

Local storm report, Jul 20, 10:43 PM CDT, 7 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO IL
1043 PM CDT SUN JUL 20 2003

TIME(CDT)  .....CITY LOCATION..... STATE  ...EVENT/REMARKS...
           ....COUNTY LOCATION....

1015 PM    LONG GROVE                IL   .75 INCH HAIL
07/20/03   LAKE                           REPORTED BY STORM
                                          SPOTTER.

The office that day

Everything else NWS Chicago, IL issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 20, 10:12 PM CDT	Special Marine Warning	LOT		93 min
Jul 20, 10:12 PM CDT	Special Marine Warning	LOT		93 min
Jul 20, 10:12 PM CDT	Special Marine Warning	LOT		93 min
Jul 20, 10:17 PM CDT	Severe Thunderstorm Warning	LOT	Kankakee	58 min
Jul 20, 11:49 PM CDT	Special Marine Warning	LOT		86 min
Jul 20, 11:49 PM CDT	Special Marine Warning	LOT		86 min
Jul 21, 1:21 AM CDT	Severe Thunderstorm Warning	LOT	Lee	54 min
Jul 21, 1:47 AM CDT	Severe Thunderstorm Warning	LOT	DeKalb	43 min
Jul 21, 2:08 AM CDT	Severe Thunderstorm Warning	LOT	Kendall, LaSalle	32 min
Jul 21, 2:16 AM CDT	Severe Thunderstorm Warning	LOT	Ford, Livingston	44 min
Jul 21, 2:26 AM CDT	Severe Thunderstorm Warning	LOT	Will	64 min
Jul 21, 2:45 AM CDT	Flash Flood Warning	LOT	Cook, Will	3 hr
Jul 21, 2:53 AM CDT	Severe Thunderstorm Warning	LOT	Iroquois	37 min
Jul 20, 11:03 PM CDT	Severe Thunderstorm Warning	LOT	Jasper	42 min
Jul 20, 11:37 PM CDT	Severe Thunderstorm Warning	LOT	Newton	38 min
Jul 21, 12:50 AM CDT	Severe Thunderstorm Warning	LOT	Jasper	25 min
Jul 21, 5:37 AM CDT	Flash Flood Warning	LOT	Jasper, Lake, Newton, Porter	113 min

Nearby

Severe Thunderstorm Warnings in Illinois, 2003 Every severe thunderstorm warning in 2003

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.