Alert archive / Illinois / Tornado Warnings in 2011

Tornado Warning 17, NWS Quad Cities, IA

August 12, 2011Stephenson County, Illinois

NWS Quad Cities, IA issued this tornado warning at Aug 12, 2011, 5:39 PM CDT for Stephenson County, Illinois. It was in force for 26 min. 3 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Aug 12, 2011, 5:39 PM CDT (22:39 UTC)
Expired: Aug 12, 2011, 6:05 PM CDT
In force: 26 min
Issued by: NWS Quad Cities, IA
Area: Storm-based polygon

County Stephenson County, IL

The radar

The Milwaukee radar (KMKX), 111 km from the middle of the area, began a volume at 22:39 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.

What was reported inside it

Time	Report	Where	Remark
Aug 12, 5:39 PM CDT	HAIL 0.88	4 N German Valley, IL	NICKEL SIZED HAIL AND SMALLER.
Aug 12, 5:40 PM CDT	HAIL 0.88	3 Nw German Valley, IL
Aug 12, 5:50 PM CDT	TSTM WND DMG	German Valley, IL	4-5 INCH DIAMETER TREE LIMBS DOWN.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Davenport, (KDVN), launched 12:00Z, 10.7 hours before the alert went out and 109 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1545 m above ground
0-6 km bulk shear: 27 kt
0-1 km storm-relative helicity: 38 m²/s²
0-3 km storm-relative helicity: 60 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.

533 
WFUS53 KDVN 122239
TORDVN
ILC177-122315-
/O.NEW.KDVN.TO.W.0017.110812T2239Z-110812T2315Z/

BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
539 PM CDT FRI AUG 12 2011

THE NATIONAL WEATHER SERVICE IN THE QUAD CITIES HAS ISSUED A

* TORNADO WARNING FOR...
  SOUTHEASTERN STEPHENSON COUNTY IN NORTHWEST ILLINOIS...

* UNTIL 615 PM CDT.

* AT 538 PM CDT...TRAINED SPOTTERS AND DOPPLER RADAR INDICATED A
  TORNADO NEAR GERMAN VALLEY...OR 11 MILES EAST OF FREEPORT...MOVING
  EAST AT 15 MPH.

* THE TORNADO WILL OTHERWISE REMAIN OVER MAINLY RURAL AREAS OF THE
  INDICATED COUNTY.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THE SAFEST PLACE TO BE IN A TORNADO IS IN A BASEMENT OR INTERIOR ROOM
OR HALLWAY ON THE LOWEST FLOOR OF A BUILDING.

&&

LAT...LON 4220 8940 4219 8953 4220 8955 4230 8955
      4230 8939 4220 8939
TIME...MOT...LOC 2239Z 271DEG 15KT 4223 8943

$$

DLF

1 follow-up statement

934 
WWUS53 KDVN 122305
SVSDVN

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
605 PM CDT FRI AUG 12 2011

ILC177-122314-
/O.CAN.KDVN.TO.W.0017.000000T0000Z-110812T2315Z/
STEPHENSON IL-
605 PM CDT FRI AUG 12 2011

...THE TORNADO WARNING FOR SOUTHEASTERN STEPHENSON COUNTY IS
CANCELLED...

THE SEVERE THUNDERSTORM THAT WAS CAPABLE OF PRODUCING A TORNADO HAS 
MOVED OUT OF THE WARNED AREA. THEREFORE THE TORNADO WARNING HAS BEEN 
CANCELLED.

LAT...LON 4220 8940 4219 8953 4220 8955 4230 8955
      4230 8939 4220 8939
TIME...MOT...LOC 2304Z 271DEG 15KT 4223 8929

$$

DLF

The office that day

Everything else NWS Quad Cities, IA issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 12, 4:43 PM CDT	Special Weather Statement	DVN	Stephenson	62 min
Aug 12, 5:23 PM CDT	Severe Thunderstorm Warning	DVN	Stephenson	22 min
Aug 12, 5:24 PM CDT	Flash Flood Warning	DVN	Stephenson	2 hr

Nearby

Tornado Warnings in Illinois, 2011 Every tornado warning in 2011 Tornadoes in 2011

Sources

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