Alert archive / Texas / Mesoscale Discussions in 2012

Mesoscale Discussion 574

April 20, 20128 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Apr 20, 2012, 4:48 PM CDT for 8 counties in Texas. It was in force for 57 min.

The area

The outline as issued.

The facts

Issued: Apr 20, 2012, 4:48 PM CDT (21:48 UTC)
Expired: Apr 20, 2012, 5:45 PM CDT
In force: 57 min
Issued by: the Storm Prediction Center

Counties Brooks County, TX, Cameron County, TX, Hidalgo County, TX, Kenedy County, TX, Kleberg County, TX, Nueces County, TX, Starr County, TX, Willacy County, TX

The radar

The Brownsville radar (KBRO), 109 km from the middle of the area, began a volume at 21:50 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

Brownsville Intl, TX (KBRO), launched 12:00Z, 9.8 hours before the alert went out and 111 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: 1336 J/kg
Mixed-layer CIN: -192 J/kg
Mixed-layer LCL: 742 m above ground
0-6 km bulk shear: 52 kt
0-1 km storm-relative helicity: 144 m²/s²
0-3 km storm-relative helicity: 151 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 2.0

Open this sounding in Storm Lab

The text

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

097 
ACUS11 KWNS 202149
SWOMCD
SPC MCD 202148
TXZ000-202245-

MESOSCALE DISCUSSION 0574
NWS STORM PREDICTION CENTER NORMAN OK
0448 PM CDT FRI APR 20 2012

AREAS AFFECTED...DEEP S TX

CONCERNING...SEVERE THUNDERSTORM WATCH 185...

VALID 202148Z - 202245Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 185
CONTINUES.

A LARGE TO VERY LARGE HAIL THREAT...IN ADDITION TO DMGG WINDS AND AN
ISOLD TORNADO RISK...WILL CONTINUE UNTIL THE STORMS OVER THE AREA
MOVE SEWD AND OFFSHORE INTO THE WRN GULF.

RADAR MOSAIC/SURFACE CHART ANALYSIS SHOWS AN EXTENSIVE SQUALL LINE
EXTENDING FROM THE MIDDLE TX COAST NEWD THROUGH THE HOUSTON METRO
VICINITY WITH A BROKEN LINE/CLUSTER OF QUASI-DISCRETE SUPERCELLS
DEVELOPING FARTHER SW OVER DEEP S TX FROM CRP TO 40 MI NNW MFE.  THE
AIRMASS IMMEDIATELY AHEAD OF THE ESEWD MOVING CONVECTIVE COMPLEX HAS
WARMED INTO THE UPPER 80S WITH MID-UPPER 60S DEWPOINTS.  THIS
POTENTIALLY UNSTABLE BOUNDARY LAYER RESIDES UNDERNEATH A STOUT CAP
/PER 18Z BRO RAOB/ WITH VERY STEEP H7-H5 LAPSE RATES /NEAR 9 DEG C
PER KM/.  HOWEVER...LARGE SCALE FORCING FOR ASCENT DUE TO AN
EQUATORWARD DIGGING UPPER TROUGH OVER TX AND LOW LEVEL LIFT OWING TO
A COLD FRONT MOVING THROUGH THE AREA WILL CONTINUE TO STRONGLY FAVOR
FURTHER STORM DEVELOPMENT.  STRONG UPPER TROPOSPHERIC FLOW SAMPLED
BY AREA 88D VAD/S AND RAOB DATA WILL SUPPORT ROTATION WITH THE
STRONGER UPDRAFTS.  THIS WILL LEND TO THE POSSIBILITY OF HAIL OF
BEING GOLFBALL SIZE OR LARGER WITH THE MOST INTENSE STORMS...OWING
TO LARGE CAPE IN THE -10 TO -30 DEG C LAYER.  AN ISOLD TORNADO RISK
CANNOT BE RULED OUT DESPITE WEAK LOW LEVEL FLOW...DUE TO VEERING LOW
LEVEL WINDS WITH HEIGHT AND SUPERCELLULAR STORM MODE.

..SMITH.. 04/20/2012

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

ATTN...WFO...CRP...BRO...

LAT...LON   26499884 27579795 27929724 27789704 25979676 26009760
            26259870 26499884

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 19, 9:13 PM CDT	Mesoscale Discussion	SPC	Cooke, Denton, Grayson, Jack, Montague, Wise	62 min
Apr 19, 10:49 PM CDT	Mesoscale Discussion	SPC	Archer, Baylor, Clay, Cooke, Foard, Hardeman and 7 more	116 min
Apr 20, 12:35 PM CDT	Mesoscale Discussion	SPC	Angelina, Aransas, Austin, Bee, Brazoria, Calhoun and 33 more	2 hr
Apr 20, 12:57 PM CDT	Severe Thunderstorm Watch	SPC	Aransas, Austin, Bastrop, Bee, Brazoria, Brazos and 43 more	7 hr
Apr 20, 1:30 PM CDT	Mesoscale Discussion	SPC	Brooks, Cameron, Duval, Hidalgo, Jim Hogg, Jim Wells and 7 more	2 hr
Apr 20, 2:29 PM CDT	Severe Thunderstorm Watch	SPC	Brooks, Cameron, Duval, Hidalgo, Jim Hogg, Jim Wells and 10 more	5 hr
Apr 20, 3:44 PM CDT	Mesoscale Discussion	SPC	Angelina, Austin, Brazoria, Brazos, Burleson, Chambers and 27 more	91 min
Apr 20, 6:12 PM CDT	Mesoscale Discussion	SPC	Aransas, Brazoria, Calhoun, Chambers, Fort Bend, Galveston and 18 more	93 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.