Alert archive / Alabama / Tornado Watches in 2011
Tornado Watch 842
The Storm Prediction Center issued this tornado watch at Sep 5, 2011, 3:49 PM CDT for 22 counties in Alabama. It was in force for 4 hr.
The area
The outline as issued.
The facts
- Issued
- Sep 5, 2011, 3:49 PM CDT (20:49 UTC)
- Expired
- Sep 5, 2011, 7:40 PM CDT
- In force
- 4 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1 in
- Strongest gust expected
- 60 kt
All 22 counties
Autauga County, AL, Barbour County, AL, Bullock County, AL, Calhoun County, AL, Chambers County, AL, Chilton County, AL, Clay County, AL, Cleburne County, AL, Coosa County, AL, Dallas County, AL, Elmore County, AL, Lee County, AL, Lowndes County, AL, Macon County, AL, Montgomery County, AL, Pike County, AL, Randolph County, AL, Russell County, AL, Shelby County, AL, St. Clair County, AL, Talladega County, AL, Tallapoosa County, AL
The radar
The Birmingham radar (KBMX), 86 km from the middle of the area, began a volume at 20:48 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
- 40%
- One or more EF2 to EF5 tornadoes
- 20%
- Ten or more severe wind reports
- 30%
- One or more gusts of 65 knots or more
- 30%
- Ten or more severe hail reports
- 5%
- One or more hailstones of 2 inches or more
- 5%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
3 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 5, 4:52 PM CDT | Flash Flood Warning | BMX | Bibb, Shelby | 3 hr |
| Sep 5, 5:12 PM CDT | Flash Flood Warning | BMX | Etowah, St. Clair | 6 hr |
| Sep 5, 7:01 PM CDT | Flash Flood Warning | BMX | Calhoun, Cherokee, Etowah, St. Clair, Shelby, Talladega | 3 hr |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
Birmingham, AL (KBMX), launched 12:00Z, 8.8 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.
- Mixed-layer CAPE
- 371 J/kg
- Mixed-layer CIN
- -4 J/kg
- Mixed-layer LCL
- 471 m above ground
- 0-6 km bulk shear
- 42 kt
- 0-1 km storm-relative helicity
- 238 m²/s²
- 0-3 km storm-relative helicity
- 277 m²/s²
- Significant tornado parameter
- 0.4
- Supercell composite
- 2.7
The text
As transmitted, in the capitals the NWS used until 2016.
174
WWUS20 KWNS 052031
SEL2
SPC WW 052031
ALZ000-060300-
URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 842
NWS STORM PREDICTION CENTER NORMAN OK
335 PM CDT MON SEP 5 2011
THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF
CENTRAL ALABAMA
EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 335 PM UNTIL
1000 PM 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 40 STATUTE
MILES EAST AND WEST OF A LINE FROM 40 MILES NORTHEAST OF ANNISTON
ALABAMA TO 40 MILES EAST OF SELMA ALABAMA. FOR A COMPLETE
DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE
(WOUS64 KWNS WOU2).
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 838...WW 840...WW 841...
DISCUSSION...SURFACE LOW SW OF MGM WILL CONTINUE TO DEVELOP NEWD
ALONG ATTENDANT BAROCLINIC ZONE ENHANCING VERTICAL SHEAR AND
CONVERGENCE ALONG IT/S TRACK. AS SUCH...THE POTENTIAL FOR
SUPERCELLS CAPABLE OF A COUPLE TORNADOES AND DAMAGING WINDS WILL
LIKELY PERSIST THROUGH THIS EVENING ACROSS THE WATCH AREA.
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 21030.
...MEADSPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 4, 9:42 PM CDT | Tornado Watch | SPC | Autauga, Baldwin, Butler, Choctaw, Clarke, Conecuh and 16 more | 9 hr |
| Sep 4, 11:35 PM CDT | Mesoscale Discussion | SPC | Baldwin, Choctaw, Clarke, Conecuh, Covington, Escambia and 6 more | 115 min |
| Sep 5, 4:26 AM CDT | Mesoscale Discussion | SPC | Autauga, Baldwin, Barbour, Bibb, Bullock, Butler and 41 more | 94 min |
| Sep 5, 5:35 AM CDT | Tornado Watch | SPC | Autauga, Baldwin, Barbour, Bibb, Blount, Bullock and 50 more | 10 hr |
| Sep 5, 7:24 AM CDT | Mesoscale Discussion | SPC | Autauga, Barbour, Bibb, Bullock, Butler, Calhoun and 20 more | 66 min |
| Sep 5, 11:01 AM CDT | Mesoscale Discussion | SPC | Autauga, Baldwin, Barbour, Bibb, Blount, Bullock and 41 more | 29 min |
| Sep 5, 3:04 PM CDT | Severe Thunderstorm Watch | SPC | Coffee, Dale, Geneva, Henry, Houston | 6 hr |
| Sep 5, 3:15 PM CDT | Mesoscale Discussion | SPC | Barbour, Bullock, Chambers, Coffee, Dale, Elmore and 9 more | 30 min |
| Sep 5, 6:37 PM CDT | Mesoscale Discussion | SPC | Barbour, Bullock, Calhoun, Chambers, Clay, Cleburne and 9 more | 113 min |
| Sep 5, 11:10 AM CDT | Tornado Watch | SPC | Bartow, Bibb, Butts, Carroll, Chattahoochee, Chattooga and 46 more | 4 hr |
| Sep 5, 12:23 PM CDT | Mesoscale Discussion | SPC | Baldwin, Burke, Columbia, Elbert, Emanuel, Glascock and 17 more | 67 min |
| Sep 5, 2:05 PM CDT | Mesoscale Discussion | SPC | Baldwin, Banks, Barrow, Bartow, Bibb, Bleckley and 75 more | 55 min |
| Sep 5, 2:42 PM CDT | Tornado Watch | SPC | Baldwin, Banks, Barrow, Bartow, Bibb, Bleckley and 81 more | 7 hr |
| Sep 5, 4:48 PM CDT | Mesoscale Discussion | SPC | Appling, Bacon, Brantley, Bryan, Bulloch, Camden and 19 more | 87 min |
| Sep 5, 5:12 PM CDT | Severe Thunderstorm Watch | SPC | Burke, Richmond | 4 hr |
Nearby
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.