Alert archive / Texas / Mesoscale Discussions in 2011

Mesoscale Discussion 511

April 21, 201132 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Apr 21, 2011, 9:15 PM CDT for 32 counties in Texas. It was in force for 60 min.

The area

The outline as issued.

The facts

Issued: Apr 21, 2011, 9:15 PM CDT (02:15 UTC)
Expired: Apr 21, 2011, 10:15 PM CDT
In force: 60 min
Issued by: the Storm Prediction Center

All 32 counties

Archer County, TX, Baylor County, TX, Callahan County, TX, Coke County, TX, Coleman County, TX, Concho County, TX, Crockett County, TX, Edwards County, TX, Fisher County, TX, Foard County, TX, Haskell County, TX, Irion County, TX, Jones County, TX, King County, TX, Knox County, TX, Menard County, TX, Mitchell County, TX, Nolan County, TX, Reagan County, TX, Runnels County, TX, Schleicher County, TX, Scurry County, TX, Shackelford County, TX, Stephens County, TX, Sterling County, TX, Stonewall County, TX, Sutton County, TX, Taylor County, TX, Terrell County, TX, Throckmorton County, TX, Tom Green County, TX, Val Verde County, TX

The radar

The San Angelo radar (KSJT), 31 km from the middle of the area, began a volume at 02:16 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

Midland Regional, TX (KMAF), launched 00:00Z, 2.3 hours before the alert went out and 168 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: 1962 J/kg
Mixed-layer CIN: -32 J/kg
Mixed-layer LCL: 2427 m above ground
0-6 km bulk shear: 40 kt
0-1 km storm-relative helicity: -18 m²/s²
0-3 km storm-relative helicity: 45 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 2.1

Open this sounding in Storm Lab

The text

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

885 
ACUS11 KWNS 220216
SWOMCD
SPC MCD 220215
TXZ000-220315-

MESOSCALE DISCUSSION 0511
NWS STORM PREDICTION CENTER NORMAN OK
0915 PM CDT THU APR 21 2011

AREAS AFFECTED...W-CNTRL AND NW TX

CONCERNING...SEVERE THUNDERSTORM WATCH 176...

VALID 220215Z - 220315Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 176
CONTINUES.

A BIMODAL SVR THREAT HAS EVOLVED OVER PORTIONS OF W AND CNTRL TX
THIS EVENING. THE FIRST AREA OF FOCUS IS ALONG A NWD RETREATING WARM
FRONT...WHERE AN ONGOING RIGHT-MOVING HP SUPERCELL IS PRIMARILY
AFFECTING FISHER AND JONES COUNTIES TX...WITH A CONFIRMED TORNADO
REPORTED.  ADDITIONAL CONVECTIVE DEVELOPMENT HAS OCCURRED TO THE NW
OF THIS STORM...WITH APPARENT NEWD PROPAGATION CONTERMINOUS TO THE
WARM FRONT. AS LLJ STRENGTHENS OVER THE NEXT FEW HRS AND FOCUSES
LOW-LEVEL WAA ALONG AND N OF THE WARM FRONT...STEEP MIDLEVEL LAPSE
RATES MAY CONTINUE TO SUPPORT ISOLATED ELEVATED THUNDERSTORMS
CAPABLE OF PRODUCING SVR HAIL.

FARTHER S...A BROKEN LINE OF THUNDERSTORMS IS SLOWLY WEAKENING
ACROSS SUTTON COUNTY TX. THE BOUNDARY LAYER DOWNSTREAM FROM THIS
LINE HAS STABILIZED WITH THE LOSS OF DIABATIC HEATING AND THE
PRESENCE OF AN 800 MB INVERSION LAYER /PER 00Z DRT SOUNDING/. GIVEN
THE PRESENCE OF STEEP MIDLEVEL LAPSE RATES...A MARGINAL THREAT FOR
SVR HAIL MAY EXIST SHOULD THUNDERSTORMS BE MAINTAINED EWD.

WW 176 IS CURRENTLY SET TO EXPIRE AT 03Z...BUT A LOCAL EXTENSION IN
TIME COULD BE CONSIDERED BY LOCAL WFOS FOR A PORTION OF THE WATCH
SHOULD THE SVR THREAT PERSIST PAST THIS TIME. AN ADDITIONAL WW IS
NOT CURRENTLY ANTICIPATED ATTM DUE TO THE EXPECTED ISOLATED NATURE
OF ANY THREAT FOR LARGE HAIL/DMGG WINDS...BUT CONVECTIVE TRENDS WILL
CONTINUE TO BE MONITORED.

..ROGERS.. 04/22/2011

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

ATTN...WFO...FWD...OUN...EWX...SJT...LUB...MAF...

LAT...LON   29150074 29710139 29750219 29990241 32770096 33690051
            34129961 34049888 33849857 31899899 29150074

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 22, 1:23 PM CDT	Mesoscale Discussion	SPC	Archer, Clay, Collin, Cooke, Delta, Denton and 18 more	97 min
Apr 22, 5:43 PM CDT	Mesoscale Discussion	SPC	Archer, Callahan, Clay, Coleman, Comanche, Cooke and 17 more	92 min
Apr 22, 6:10 PM CDT	Severe Thunderstorm Watch	SPC	Archer, Brown, Callahan, Clay, Coke, Coleman and 21 more	6 hr

Nearby

Mesoscale Discussions in Texas, 2011 Every mesoscale discussion in 2011

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.