Alert archive / Texas / Tornado Watches in 2012
Tornado Watch 274
The Storm Prediction Center issued this tornado watch at May 11, 2012, 7:36 PM CDT for 17 counties in Texas. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- May 11, 2012, 7:36 PM CDT (00:36 UTC)
- Expired
- May 12, 2012, 2:00 AM CDT
- In force
- 6 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1.5 in
- Strongest gust expected
- 60 kt
Counties Brazoria County, TX, Chambers County, TX, Fort Bend County, TX, Galveston County, TX, Hardin County, TX, Harris County, TX, Jasper County, TX, Jefferson County, TX, Liberty County, TX, Montgomery County, TX, Newton County, TX, Orange County, TX, Polk County, TX, San Jacinto County, TX, Trinity County, TX, Tyler County, TX, Walker County, TX
The radar
The Houston radar (KHGX), 70 km from the middle of the area, began a volume at 00:40 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
- 20%
- One or more gusts of 65 knots or more
- 20%
- Ten or more severe hail reports
- 30%
- One or more hailstones of 2 inches or more
- 20%
- Six or more combined severe hail and wind reports
- 50%
Warnings issued inside it
8 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 11, 8:00 PM CDT | Severe Thunderstorm Warning | HGX | Fort Bend, Harris, Waller | 45 min |
| May 11, 8:08 PM CDT | Severe Thunderstorm Warning | HGX | Polk, San Jacinto, Trinity, Walker | 52 min |
| May 11, 8:29 PM CDT | Severe Thunderstorm Warning | HGX | Fort Bend, Harris | 46 min |
| May 11, 9:37 PM CDT | Severe Thunderstorm Warning | HGX | Fort Bend, Harris, Waller | 38 min |
| May 11, 10:14 PM CDT | Severe Thunderstorm Warning | HGX | Fort Bend, Harris | 46 min |
| May 11, 10:57 PM CDT | Severe Thunderstorm Warning | HGX | Brazoria, Fort Bend, Harris | 48 min |
| May 11, 11:29 PM CDT | Severe Thunderstorm Warning | HGX | Chambers, Galveston, Harris | 61 min |
| May 12, 12:29 AM CDT | Severe Thunderstorm Warning | HGX | Chambers, Galveston | 31 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
Lake Charles Mun, LA (KLCH), launched 00:00Z, 0.6 hours before the alert went out and 157 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
- 21 J/kg
- Mixed-layer CIN
- -209 J/kg
- Mixed-layer LCL
- 694 m above ground
- 0-6 km bulk shear
- 40 kt
- 0-1 km storm-relative helicity
- 45 m²/s²
- 0-3 km storm-relative helicity
- 117 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- -0.2
The text
As transmitted, in the capitals the NWS used until 2016.
919
WWUS20 KWNS 120039
SEL4
SPC WW 120039
TXZ000-CWZ000-120700-
URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 274
NWS STORM PREDICTION CENTER NORMAN OK
740 PM CDT FRI MAY 11 2012
THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF
SOUTHEAST TEXAS
COASTAL WATERS
EFFECTIVE THIS FRIDAY NIGHT AND SATURDAY MORNING FROM 740 PM
UNTIL 200 AM CDT.
TORNADOES...HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.
THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 60 STATUTE
MILES NORTH AND SOUTH OF A LINE FROM 20 MILES WEST OF HOUSTON
TEXAS TO 30 MILES NORTHEAST OF PORT ARTHUR TEXAS. FOR A COMPLETE
DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE
(WOUS64 KWNS WOU4).
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.
DISCUSSION...DISCRETE STORMS ARE EXPECTED TO PERSIST AND MAY
INCREASE IN COVERAGE AND INTENSITY FROM HOUSTON AREA EAST TO THE
SABINE PASS THROUGH THE LATE EVENING. RICH LOW LEVEL MOISTURE BEING
LIFTED ACROSS A WEAK WARM FRONT ACROSS THESE AREAS APPEARS TO BE
CONTRIBUTING TO TSTM DEVELOPMENT AND MAY BE FURTHER AIDED AS LARGE
SCALE UPPER TROUGH APPROACHES THE REGION TONIGHT. DEEP-LAYER
VERTICAL SHEAR IS SUFFICIENT TO MAINTAIN ORGANIZED UPDRAFTS WHILE
LOW LEVEL STORM RELATIVE SHEAR NEAR AND ALONG THE WARM FRONT WILL
OCCASIONALLY FAVOR LOW LEVEL UPDRAFT ROTATION AND A CHANCE FOR A
TORNADO OR TWO. THIS TORNADO POTENTIAL WILL ALSO BE SUPPORTED BY
HIGH BOUNDARY LAYER RH AND LOW LFC LEVELS AOB 1KM.
AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
450. MEAN STORM MOTION VECTOR 27025.
...CARBINSPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 11, 7:28 PM CDT | Mesoscale Discussion | SPC | Austin, Brazoria, Chambers, Fort Bend, Hardin, Harris and 10 more | 32 min |
| May 11, 10:31 PM CDT | Mesoscale Discussion | SPC | Brazoria, Chambers, Fort Bend, Galveston, Hardin, Harris and 11 more | 89 min |
| May 12, 1:40 AM CDT | Mesoscale Discussion | SPC | Brazoria, Chambers, Fort Bend, Galveston, Hardin, Harris and 11 more | 65 min |
| May 12, 4:20 PM CDT | Mesoscale Discussion | SPC | Brooks, Cameron, Hidalgo, Willacy | 55 min |
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.