Alert archive / Tennessee / Tornado Watches in 2011
Tornado Watch 165
The Storm Prediction Center issued this tornado watch at Apr 20, 2011, 2:42 AM EDT for 48 counties in Tennessee. It was in force for 5 hr.
The area
The outline as issued.
The facts
- Issued
- Apr 20, 2011, 2:42 AM EDT (06:42 UTC)
- Expired
- Apr 20, 2011, 8:04 AM EDT
- In force
- 5 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1 in
- Strongest gust expected
- 60 kt
All 48 counties
Anderson County, TN, Bledsoe County, TN, Blount County, TN, Bradley County, TN, Campbell County, TN, Cannon County, TN, Carter County, TN, Claiborne County, TN, Cocke County, TN, Coffee County, TN, Cumberland County, TN, DeKalb County, TN, Fentress County, TN, Franklin County, TN, Grainger County, TN, Greene County, TN, Grundy County, TN, Hamblen County, TN, Hamilton County, TN, Hancock County, TN, Hawkins County, TN, Jefferson County, TN, Johnson County, TN, Knox County, TN, Lincoln County, TN, Loudon County, TN, Marion County, TN, McMinn County, TN, Meigs County, TN, Monroe County, TN, Moore County, TN, Morgan County, TN, Overton County, TN, Pickett County, TN, Polk County, TN, Putnam County, TN, Rhea County, TN, Roane County, TN, Scott County, TN, Sequatchie County, TN, Sevier County, TN, Sullivan County, TN, Unicoi County, TN, Union County, TN, Van Buren County, TN, Warren County, TN, Washington County, TN, White County, TN
The radar
The Nashville radar (KOHX), 142 km from the middle of the area, began a volume at 06:42 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 SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 30%
- One or more EF2 to EF5 tornadoes
- 20%
- Ten or more severe wind reports
- 50%
- One or more gusts of 65 knots or more
- 10%
- Ten or more severe hail reports
- 10%
- One or more hailstones of 2 inches or more
- 5%
- Six or more combined severe hail and wind reports
- 80%
Warnings issued inside it
4 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 20, 3:09 AM EDT | Severe Thunderstorm Warning | OHX | Clay, Cumberland, DeKalb, Fentress, Jackson, Macon and 7 more | 36 min |
| Apr 20, 3:11 AM EDT | Severe Thunderstorm Warning | OHX | Bedford, Cannon, Coffee, Cumberland, DeKalb, Giles and 8 more | 64 min |
| Apr 20, 4:11 AM EDT | Severe Thunderstorm Warning | OHX | Coffee, Cumberland, Fentress, Grundy, Overton, Putnam and 3 more | 49 min |
| Apr 20, 4:17 AM EDT | Severe Thunderstorm Warning | MRX | Anderson, Campbell, Morgan, Scott | 58 min |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
Nashville Metro, TN (KBNA), launched 00:00Z, 6.7 hours before the alert went out and 143 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.
- Mixed-layer CAPE
- 1997 J/kg
- Mixed-layer CIN
- -93 J/kg
- Mixed-layer LCL
- 1626 m above ground
- 0-6 km bulk shear
- 29 kt
- 0-1 km storm-relative helicity
- 92 m²/s²
- 0-3 km storm-relative helicity
- 239 m²/s²
- Significant tornado parameter
- 0.4
- Supercell composite
- 7.7
The text
As transmitted, in the capitals the NWS used until 2016.
087
WWUS20 KWNS 200643
SEL5
SPC WW 200643
TNZ000-201400-
URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 165
NWS STORM PREDICTION CENTER NORMAN OK
245 AM EDT WED APR 20 2011
THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF
EASTERN TENNESSEE
EFFECTIVE THIS WEDNESDAY MORNING FROM 245 AM UNTIL 1000 AM EDT.
TORNADOES...HAIL TO 1 INCH IN DIAMETER...THUNDERSTORM WIND GUSTS
TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.
THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 80 STATUTE
MILES EAST AND WEST OF A LINE FROM 55 MILES NORTH OF KNOXVILLE
TENNESSEE TO 35 MILES WEST OF CHATTANOOGA TENNESSEE. FOR A
COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
UPDATE (WOUS64 KWNS WOU5).
REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS.
OTHER WATCH INFORMATION...CONTINUE...WW 157...WW 159...WW
160...WW 161...WW 162...WW 163...WW 164...
DISCUSSION...SRN END OF KY/MIDDLE TN SQLN WILL CONTINUE ENEWD INTO E
TN THROUGH LATER THIS MORNING. COMBINATION OF RISING TERRAIN AND
CONTINUED EWD SPREAD OF MOISTURE ALONG 50-60 KT SWLY LLJ SHOULD
MAINTAIN STRENGTH OF EMBEDDED STORMS...AND ATTENDANT THREAT FOR DMGG
WIND AND ISOLD TORNADOES.
AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 1 INCH. EXTREME TURBULENCE AND SURFACE WIND
GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500.
MEAN STORM MOTION VECTOR 25040.
...CORFIDISPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 19, 9:07 PM EDT | Mesoscale Discussion | SPC | Dyer, Lake, Lauderdale, Obion, Tipton | 83 min |
| Apr 19, 10:39 PM EDT | Mesoscale Discussion | SPC | Bedford, Benton, Cannon, Carroll, Cheatham, Chester and 23 more | 66 min |
| Apr 19, 11:14 PM EDT | Tornado Watch | SPC | Bedford, Benton, Carroll, Cheatham, Chester, Clay and 31 more | 7 hr |
| Apr 20, 12:56 AM EDT | Mesoscale Discussion | SPC | Bedford, Benton, Bledsoe, Campbell, Cannon, Carroll and 55 more | 94 min |
| Apr 20, 3:20 AM EDT | Mesoscale Discussion | SPC | Anderson, Bledsoe, Campbell, Claiborne, Clay, Cumberland and 23 more | 85 min |
Nearby
Tornado Watches in Tennessee, 2011Every tornado watch 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.