Alert archive / Texas / Mesoscale Discussions in 2012

Mesoscale Discussion 792

May 11, 201217 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at May 11, 2012, 10:31 PM CDT for 17 counties in Texas. It was in force for 89 min.

The area

The outline as issued.

The facts

Issued: May 11, 2012, 10:31 PM CDT (03:31 UTC)
Expired: May 12, 2012, 12:00 AM CDT
In force: 89 min
Issued by: the Storm Prediction Center

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), 61 km from the middle of the area, began a volume at 03:34 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.

The nearest sounding before it

Lake Charles Mun, LA (KLCH), launched 00:00Z, 3.5 hours before the alert went out and 148 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: 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

Open this sounding in Storm Lab

The text

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

634 
ACUS11 KWNS 120332
SWOMCD
SPC MCD 120331
LAZ000-TXZ000-120500-

MESOSCALE DISCUSSION 0792
NWS STORM PREDICTION CENTER NORMAN OK
1031 PM CDT FRI MAY 11 2012

AREAS AFFECTED...SOUTH TX

CONCERNING...TORNADO WATCH 274...

VALID 120331Z - 120500Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 274 CONTINUES.

SUMMARY...THE SEVERE THREAT ACROSS WW 274 SHOULD CONTINUE FOR
SEVERAL MORE HOURS. AN ISOLATED TORNADO THREAT ALONG WITH LARGE HAIL
AND WIND DAMAGE WILL BE POSSIBLE WITH THE MORE INTENSE CELLS. THE
THREATS COULD PERSIST UNTIL WATCH EXPIRATION AT 07Z ESPECIALLY IF
STORMS CAN REDEVELOP ACROSS THE WRN PART OF THE WATCH.

DISCUSSION...A SUPERCELL SOUTHWEST OF THE HOUSTON AREA IS LOCATED
ALONG THE NRN EDGE OF MODERATE INSTABILITY WHERE MLCAPE VALUES ARE
ESTIMATED FROM 1000 TO 1500 J/KG. THE CONVECTION IS LOCATED ALONG A
QUASI-STATIONARY FRONT AND AHEAD OF A BAND OF LARGE-SCALE ASCENT
EVIDENT ON WATER VAPOR/RUC IMAGERY. THE INSTABILITY AND LIFT SHOULD
SUPPORT CONTINUED DEVELOPMENT OF THUNDERSTORM ACTIVITY ESPECIALLY ON
THE WRN SIDE OF THE WATCH. THE LATEST WSR-88D VWP FROM HOUSTON SHOWS
40 TO 50 KT OF DEEP LAYER SHEAR WITH 25 KT OF FLOW AT 850 MB. THIS
AMOUNT OF FLOW WILL CONTINUE TO SUPPORT SUPERCELL DEVELOPMENT AND AN
ISOLATED TORNADO OR TWO WILL BE POSSIBLE. WIND DAMAGE AND HAIL WILL
MAY ALSO OCCUR WITH THE WRN PART OF THE WATCH FAVORED DUE TO STRONG
INSTABILITY.

..BROYLES.. 05/12/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...LCH...SHV...HGX...

LAT...LON   28589505 29209427 29379375 29439336 29759333 29689387
            29809392 29849378 30229367 30399371 30599371 30889355
            31189352 31039431 31049462 31169482 31349492 30969555
            30849581 30089578 30119595 29819582 29729599 29589602
            29249587 28879569 28829542 28929527 28639510 28589505

SPC 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, 7:36 PM CDT	Tornado Watch	SPC	Brazoria, Chambers, Fort Bend, Galveston, Hardin, Harris and 11 more	6 hr
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

Mesoscale Discussions in Texas, 2012 Every mesoscale discussion in 2012

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.