Alert archive / Tennessee / Tornado Watches in 2007

Tornado Watch 718

October 18, 20074 states

The Storm Prediction Center issued this tornado watch at Oct 18, 2007, 1:31 AM CDT for 4 states. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued
Oct 18, 2007, 1:31 AM CDT (06:31 UTC)
Expired
Oct 18, 2007, 5:37 AM CDT
In force
4 hr
Issued by
the Storm Prediction Center
Largest hail expected
1 in
Strongest gust expected
60 kt
All 47 counties

Clay County, AR, Craighead County, AR, Crittenden County, AR, Cross County, AR, Greene County, AR, Lawrence County, AR, Lee County, AR, Mississippi County, AR, Phillips County, AR, Poinsett County, AR, Randolph County, AR, St. Francis County, AR, Dunklin County, MO, Pemiscot County, MO, Alcorn County, MS, Benton County, MS, Coahoma County, MS, DeSoto County, MS, Lafayette County, MS, Marshall County, MS, Panola County, MS, Quitman County, MS, Tate County, MS, Tippah County, MS, Tishomingo County, MS, Tunica County, MS, Union County, MS, Carroll County, TN, Chester County, TN, Crockett County, TN, Decatur County, TN, Dyer County, TN, Fayette County, TN, Gibson County, TN, Hardeman County, TN, Hardin County, TN, Haywood County, TN, Henderson County, TN, Henry County, TN, Lake County, TN, Lauderdale County, TN, Madison County, TN, McNairy County, TN, Obion County, TN, Shelby County, TN, Tipton County, TN, Weakley County, TN

The radar

The Memphis radar (KNQA), 30 km from the middle of the area, began a volume at 06:34 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
40%
One or more gusts of 65 knots or more
20%
Ten or more severe hail reports
20%
One or more hailstones of 2 inches or more
5%
Six or more combined severe hail and wind reports
70%

Warnings issued inside it

2 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

IssuedProductOfficeCountiesLasted
Oct 18, 3:06 AM CDTTornado WarningMEGCrittenden54 min
Oct 18, 3:50 AM CDTTornado WarningMEGMississippi39 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

Little Rock, AR (KLZK), launched 00:00Z, 6.5 hours before the alert went out and 86 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-pSkew-T log-p diagram, Little Rock, AR at 00:00Z on 2007-10-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 18 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Little Rock, AR at 00:00Z on 2007-10-18The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 152 square meters per square second.1939587897Sfc1 km3 km6 km9 kmRMLM
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
18 J/kg
Mixed-layer CIN
-168 J/kg
Mixed-layer LCL
1339 m above ground
0-6 km bulk shear
57 kt
0-1 km storm-relative helicity
152 m²/s²
0-3 km storm-relative helicity
207 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.6

Open this sounding in Storm Lab

The text

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

000
WWUS20 KWNS 180631
SEL8  
SPC WW 180631
ARZ000-MOZ000-MSZ000-TNZ000-181400-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 718
NWS STORM PREDICTION CENTER NORMAN OK
130 AM CDT THU OCT 18 2007

THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF 

       EASTERN ARKANSAS
       THE MISSOURI BOOTHEEL
       NORTHERN MISSISSIPPI
       WESTERN TENNESSEE

EFFECTIVE THIS THURSDAY MORNING FROM 130 AM UNTIL 900 AM CDT.

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 40 MILES NORTH NORTHEAST OF
DYERSBURG TENNESSEE TO 25 MILES SOUTHWEST OF OXFORD MISSISSIPPI. 
FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU8).

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 715...WW 716...WW 717...

DISCUSSION...NE AR SQLN IS ON LEADING EDGE OF ASCENT ASSOCIATED WITH
SRN PART OF POTENT NEGATIVE TILT SHORTWAVE TROUGH OVER ERN KS.  VERY
STRONG DEEP SHEAR...300+ M2/S2 0-1 KM SRH /GIVEN OBSERVED STORM
MOTIONS/ AND RICH BOUNDARY LYR MOISTURE MOVING N THROUGH THE MS
DELTA SUGGEST POTENTIAL FOR SPIN-UP TORNADOES...IN ADDITION TO
DAMAGING WIND... DESPITE QUASI-LINEAR STORM MODE.

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 450.
MEAN STORM MOTION VECTOR 22040.


...CORFIDI

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Oct 17, 7:09 PM CDTTornado WatchSPCAshley, Chicot, Clay, Craighead, Crittenden, Cross and 8 more7 hr
Oct 17, 8:10 PM CDTMesoscale DiscussionSPCAshley, Baxter, Benton, Boone, Bradley, Calhoun and 48 more95 min
Oct 17, 10:56 PM CDTMesoscale DiscussionSPCArkansas, Baxter, Boone, Bradley, Calhoun, Carroll and 64 more64 min
Oct 17, 11:38 PM CDTTornado WatchSPCArkansas, Baxter, Boone, Bradley, Calhoun, Clark and 39 more3 hr
Oct 18, 12:27 AM CDTMesoscale DiscussionSPCCraighead, Crittenden, Cross, Lee, Mississippi, Phillips and 2 more93 min
Oct 18, 2:02 AM CDTMesoscale DiscussionSPCArkansas, Baxter, Clay, Cleburne, Cleveland, Conway and 27 more58 min
Oct 18, 4:08 AM CDTMesoscale DiscussionSPCCraighead, Crittenden, Cross, Greene, Mississippi, Poinsett67 min
Oct 18, 1:31 PM CDTTornado WatchSPCClay, Craighead, Crittenden, Cross, Greene, Lee and 4 more9 hr
Oct 18, 5:39 PM CDTMesoscale DiscussionSPCCrittenden, Mississippi66 min
Oct 18, 3:02 AM CDTMesoscale DiscussionSPCGreene, Wayne58 min
Oct 18, 10:26 AM CDTMesoscale DiscussionSPCAlcorn, Benton, Calhoun, Carroll, Chickasaw, Choctaw and 27 more2 hr
Oct 18, 3:52 PM CDTMesoscale DiscussionSPCGeorge83 min
Oct 17, 7:57 PM CDTMesoscale DiscussionSPCAdair, Audrain, Barry, Barton, Bates, Benton and 59 more63 min
Oct 17, 11:40 PM CDTTornado WatchSPCAudrain, Bollinger, Boone, Butler, Callaway, Cape Girardeau and 43 more4 hr

Nearby

Tornado Watches in Tennessee, 2007Tornado Watches in Mississippi, 2007Tornado Watches in Arkansas, 2007Every tornado watch in 2007

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.