Alert archive / Nebraska / Tornado Warnings in 2011

Tornado Warning 82, NWS Omaha, NE

August 18, 2011Knox County, Nebraska

NWS Omaha, NE issued this tornado warning at Aug 18, 2011, 7:02 PM CDT for Knox County, Nebraska. It was in force for 31 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Aug 18, 2011, 7:02 PM CDT (00:02 UTC)
Expired: Aug 18, 2011, 7:33 PM CDT
In force: 31 min
Issued by: NWS Omaha, NE
Area: Storm-based polygon

County Knox County, NE

The radar

The Sioux Falls radar (KFSD), 122 km from the middle of the area, began a volume at 00:02 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 watch it was issued in

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

Issued	Product	Office	Lasted
Aug 18, 1:27 PM CDT	Severe Thunderstorm Watch	SPC	8 hr
Aug 18, 6:38 PM CDT	Tornado Watch	SPC	5 hr

The nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 0.0 hours before the alert went out and 202 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: 1385 J/kg
Mixed-layer CIN: -135 J/kg
Mixed-layer LCL: 582 m above ground
0-6 km bulk shear: 66 kt
0-1 km storm-relative helicity: 289 m²/s²
0-3 km storm-relative helicity: 636 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 47.4

Open this sounding in Storm Lab

The text

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

123 
WFUS53 KOAX 190002
TOROAX
NEC107-190045-
/O.NEW.KOAX.TO.W.0082.110819T0002Z-110819T0045Z/

BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE OMAHA/VALLEY NEBRASKA
702 PM CDT THU AUG 18 2011

THE NATIONAL WEATHER SERVICE IN OMAHA HAS ISSUED A

* TORNADO WARNING FOR...
  NORTHERN KNOX COUNTY IN NORTHEAST NEBRASKA...

* UNTIL 745 PM CDT

* AT 655 PM CDT...TRAINED WEATHER SPOTTERS REPORTED A POSSIBLE       
  TORNADO 8 MILES NORTH OF NIOBRARA...OR 34 MILES WEST OF YANKTON.   
  DOPPLER RADAR SHOWED THIS POSSIBLE TORNADO MOVING SOUTHEAST AT 35  
  MPH.

* LOCATIONS IMPACTED INCLUDE...
  NIOBRARA...SANTEE...AND CROFTON.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

TO REPEAT...A TORNADO IS ON THE GROUND. TAKE COVER NOW. MOVE TO AN
INTERIOR ROOM ON THE LOWEST FLOOR OF A STURDY BUILDING. AVOID
WINDOWS. IF IN A MOBILE HOME...A VEHICLE OR OUTDOORS...MOVE TO THE
CLOSEST SUBSTANTIAL SHELTER AND PROTECT YOURSELF FROM FLYING DEBRIS.

&&

LAT...LON 4285 9770 4285 9766 4286 9761 4285 9757
      4286 9750 4285 9748 4282 9748 4250 9750
      4265 9823 4284 9815 4277 9806 4277 9800
      4277 9795 4279 9792 4281 9789 4286 9788
      4287 9785
TIME...MOT...LOC 0000Z 302DEG 45KT 4282 9799

$$

ZAPOTOCNY

1 follow-up statement

411 
WWUS53 KOAX 190033
SVSOAX

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NEBRASKA
733 PM CDT THU AUG 18 2011

NEC107-190043-
/O.CAN.KOAX.TO.W.0082.000000T0000Z-110819T0045Z/
KNOX NE-
733 PM CDT THU AUG 18 2011

...THE TORNADO WARNING FOR NORTHERN KNOX COUNTY IS CANCELLED...

THE STORM WHICH PROMPTED THE WARNING HAS WEAKENED BELOW SEVERE
LIMITS...AND NO LONGER POSES AN IMMEDIATE THREAT TO LIFE OR PROPERTY.
 HOWEVER SMALL HAIL AND GUSTY WINDS ARE STILL POSSIBLE WITH THIS     
 THUNDERSTORM.

LAT...LON 4285 9770 4285 9766 4286 9761 4285 9757
      4286 9750 4285 9748 4282 9748 4250 9750
      4265 9823 4284 9815 4277 9806 4277 9800
      4277 9795 4279 9792 4281 9789 4286 9788
      4287 9785
TIME...MOT...LOC 0033Z 302DEG 45KT 4259 9752

$$

ZAPOTOCNY

The office that day

Everything else NWS Omaha, NE issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 18, 7:15 PM CDT	Severe Thunderstorm Warning	OAX	Douglas, Sarpy, Washington	45 min
Aug 18, 7:21 PM CDT	Tornado Warning	OAX	Antelope, Boone, Madison	39 min
Aug 18, 7:25 PM CDT	Severe Thunderstorm Warning	OAX	Antelope, Madison, Stanton	35 min
Aug 18, 7:36 PM CDT	Severe Thunderstorm Warning	OAX	Cass, Sarpy	39 min
Aug 18, 7:45 PM CDT	Tornado Warning	OAX	Boone, Butler, Madison, Platte	30 min
Aug 18, 7:47 PM CDT	Severe Thunderstorm Warning	OAX	Cass, Lancaster, Sarpy, Saunders	43 min
Aug 18, 8:11 PM CDT	Severe Thunderstorm Warning	OAX	Cass, Lancaster, Otoe	49 min
Aug 18, 8:18 PM CDT	Severe Thunderstorm Warning	OAX	Boone, Butler, Colfax, Platte	42 min
Aug 18, 8:34 PM CDT	Flash Flood Warning	OAX	Cass, Otoe, Sarpy	6 hr
Aug 18, 8:40 PM CDT	Flash Flood Warning	OAX	Platte	77 min
Aug 18, 8:50 PM CDT	Severe Thunderstorm Warning	OAX	Butler, Seward	40 min
Aug 18, 8:55 PM CDT	Severe Thunderstorm Warning	OAX	Cass, Gage, Johnson, Lancaster, Nemaha, Otoe	38 min
Aug 18, 9:13 PM CDT	Severe Thunderstorm Warning	OAX	Johnson, Nemaha, Pawnee, Richardson	47 min
Aug 18, 9:20 PM CDT	Severe Thunderstorm Warning	OAX	Saline, Seward	40 min
Aug 18, 9:35 PM CDT	Areal Flood Advisory	OAX	Cass, Johnson, Lancaster, Nemaha, Otoe	3 hr
Aug 18, 9:49 PM CDT	Severe Thunderstorm Warning	OAX	Gage, Johnson, Lancaster, Otoe, Saline, Seward	41 min
Aug 18, 10:25 PM CDT	Severe Thunderstorm Warning	OAX	Gage, Jefferson, Johnson, Pawnee, Saline	50 min
Aug 18, 11:19 PM CDT	Severe Thunderstorm Warning	OAX	Colfax, Madison, Platte, Stanton	41 min

Nearby

Tornado Warnings in Nebraska, 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.