Alert archive / Illinois / Mesoscale Discussions in 2003

Mesoscale Discussion 1997

July 27, 200325 counties in Illinois; Clinton County, Scott County, Iowa

The Storm Prediction Center issued this mesoscale discussion at Jul 27, 2003, 10:44 AM CDT for 25 counties in Illinois; Clinton County, Scott County, Iowa. It was in force for 91 min.

The area

The outline as issued.

The facts

Issued: Jul 27, 2003, 10:44 AM CDT (15:44 UTC)
Expired: Jul 27, 2003, 12:15 PM CDT
In force: 91 min
Issued by: the Storm Prediction Center

All 27 counties

Clinton County, IA, Scott County, IA, Boone County, IL, Bureau County, IL, Carroll County, IL, DeKalb County, IL, DuPage County, IL, Grundy County, IL, Henry County, IL, Jo Daviess County, IL, Kane County, IL, Kankakee County, IL, Kendall County, IL, Knox County, IL, LaSalle County, IL, Lee County, IL, Marshall County, IL, McHenry County, IL, Mercer County, IL, Ogle County, IL, Putnam County, IL, Rock Island County, IL, Stark County, IL, Stephenson County, IL, Whiteside County, IL, Will County, IL, Winnebago County, IL

The radar

The Chicago radar (KLOT), 85 km from the middle of the area, began a volume at 15:47 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.

The watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Severe Thunderstorm Watch 807Jul 27, 11:30 AM CDT

The nearest sounding before it

Davenport, (KDVN), launched 12:00Z, 3.7 hours before the alert went out and 116 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: 1771 J/kg
Mixed-layer CIN: -197 J/kg
Mixed-layer LCL: 1038 m above ground
0-6 km bulk shear: 18 kt
0-1 km storm-relative helicity: 85 m²/s²
0-3 km storm-relative helicity: 74 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

480 
ACUS11 KWNS 271544
SWOMCD
SPC MCD 271544 
ILZ000-WIZ000-IAZ000-271715-

MESOSCALE DISCUSSION 1997
NWS STORM PREDICTION CENTER NORMAN OK
1044 AM CDT SUN JUL 27 2003

AREAS AFFECTED...EXTREME ERN IA...NRN IL

CONCERNING...SEVERE THUNDERSTORM POTENTIAL 

VALID 271544Z - 271715Z

EXPECT STRONG TO SEVERE TSTMS TO INCREASE ACROSS PORTIONS OF NRN IL
OVER THE NEXT FEW HOURS. A SEVERE TSTM WATCH MAY BE NECESSARY WITHIN
THE NEXT HOUR.

IT APPEARS THAT STORMS ALONG THE LEADING EDGE OF OVERNIGHT MCS
ACROSS ERN IA WERE BEGINNING TO BECOME SURFACE-BASED NEAR COLD
FRONT/OUTFLOW BOUNDARY INTERSECTION BETWEEN DVN AND MLI. AIRMASS
AHEAD OF THIS AREA OF STRONG LOW LEVEL CONVERGENCE CONTINUES TO
DESTABILIZE WITH LATEST ESTIMATED MLCAPE VALUES AOA 1500 J/KG.
DESPITE RELATIVELY WARM TEMPS ALOFT...FAVORABLE MESOSCALE FORCING
FOR ASCENT ALONG THE FRONT/OUTFLOW...AND LARGE SCALE LIFT WITHIN
RIGHT ENTRANCE REGION OF MID/UPPER JET INDICATE CONVECTIVE
DEVELOPMENT AND INTENSITY SHOULD INCREASE OVER THE NEXT FEW HOURS.
VERTICAL SHEAR WILL REMAIN MARGINAL FOR STORM ORGANIZATION BUT
MAGNITUDE OF FORCING AND INSTABILITY NEAR THE FRONT SUGGEST THAT A
FEW DAMAGING WIND AND HAIL EVENTS WILL BE POSSIBLE.

..CARBIN.. 07/27/2003

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...LOT...ILX...MKX...DVN...

41248755 40918812 40919031 41099101 41679073 42589019
42578873 42078778

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 27, 11:30 AM CDT	Severe Thunderstorm Watch	SPC	Bureau, DuPage, Ford, Grundy, Iroquois, Kankakee and 10 more	6 hr
Jul 27, 2:29 PM CDT	Mesoscale Discussion	SPC	Cook, DuPage, Ford, Grundy, Iroquois, Kankakee and 7 more	91 min

Nearby

Mesoscale Discussions in Illinois, 2003 Mesoscale Discussions in Iowa, 2003 Every mesoscale discussion 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.