Alert archive / Texas / Mesoscale Discussions in 2011
Mesoscale Discussion 841
The Storm Prediction Center issued this mesoscale discussion at May 21, 2011, 5:42 PM CDT for 8 counties in Oklahoma; 34 counties in Texas. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- May 21, 2011, 5:42 PM CDT (22:42 UTC)
- Expired
- May 21, 2011, 7:45 PM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
All 42 counties
Bryan County, OK, Carter County, OK, Garvin County, OK, Jefferson County, OK, Johnston County, OK, Love County, OK, Marshall County, OK, Murray County, OK, Bell County, TX, Blanco County, TX, Bosque County, TX, Burnet County, TX, Collin County, TX, Cooke County, TX, Coryell County, TX, Dallas County, TX, Denton County, TX, Ellis County, TX, Erath County, TX, Gillespie County, TX, Grayson County, TX, Hamilton County, TX, Hays County, TX, Hill County, TX, Hood County, TX, Johnson County, TX, Kendall County, TX, Kerr County, TX, Lampasas County, TX, Llano County, TX, Mason County, TX, McLennan County, TX, Mills County, TX, Montague County, TX, Parker County, TX, Real County, TX, San Saba County, TX, Somervell County, TX, Tarrant County, TX, Travis County, TX, Williamson County, TX, Wise County, TX
The radar
The Dallas/Ft Worth radar (KFWS), 95 km from the middle of the area, began a volume at 22:43 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 watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Fort Worth, TX (KFWD), launched 12:00Z, 10.7 hours before the alert went out and 116 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
- 87 J/kg
- Mixed-layer CIN
- -337 J/kg
- Mixed-layer LCL
- 1835 m above ground
- 0-6 km bulk shear
- 56 kt
- 0-1 km storm-relative helicity
- 203 m²/s²
- 0-3 km storm-relative helicity
- 181 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- -0.0
The text
As transmitted, in the capitals the NWS used until 2016.
814
ACUS11 KWNS 212242
SWOMCD
SPC MCD 212242
OKZ000-TXZ000-220045-
MESOSCALE DISCUSSION 0841
NWS STORM PREDICTION CENTER NORMAN OK
0542 PM CDT SAT MAY 21 2011
AREAS AFFECTED...CENTRAL TX
CONCERNING...SEVERE THUNDERSTORM WATCH 316...
VALID 212242Z - 220045Z
THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 316
CONTINUES.
LATEST VISIBLE IMAGERY SHOWS A WWD RETREAT OF THE DRYLINE ACROSS THE
EDWARDS PLATEAU REGION OF TX...WITH A SLOWER WWD MOVE FARTHER N INTO
N CENTRAL TX/SRN OK. CLUSTER OF SUPERCELLS ACROSS
BURNET/LAMPASAS/CORYELL COUNTIES REMAINS CAPABLE OF PRODUCING LARGE
HAIL AND DAMAGING GUSTS -- AND POSSIBLY A BRIEF TORNADO.
MEANWHILE...NEW CELLS ARE DEVELOPING INVOF THE RETREATING DRYLINE
JUST W OF THE ONGOING STORMS...WITH SOME SEVERE THREAT STILL
APPARENT ACROSS THIS AREA/AHEAD OF THE DRYLINE.
EXPECT SEVERE THREAT TO CONTINUE FOR THE NEXT SEVERAL HOURS...AS
MODERATE INSTABILITY COMBINED WITH FAVORABLY VEERING/INCREASING FLOW
WITH HEIGHT SUPPORT SUPERCELL ORGANIZATION.
N OF THE WATCH...ISOLATED/DEEPENING CU TOWERS ARE APPARENT ACROSS N
TX AND SRN OK INVOF THE MORE SLOWLY RETREATING DRYLINE. WITH
BACKGROUND THERMODYNAMIC AND KINEMATIC ENVIRONMENT JUST AS FAVORABLE
FOR SUPERCELLS AS AREAS FARTHER S...WE WILL CONTINUE TO MONITOR THIS
REGION -- THOUGH ATTM WE REMAIN UNCERTAIN WITH RESPECT TO THE NEED
FOR A NEW WW.
..GOSS.. 05/21/2011
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...FWD...OUN...EWX...SJT...
LAT...LON 29810006 30249995 31489889 32539808 33309794 34679780
34799691 34369609 32489651 31289704 29829792 29810006SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 20, 9:06 PM CDT | Mesoscale Discussion | SPC | Bowie, Camp, Cass, Cherokee, Gregg, Harrison and 7 more | 114 min |
| May 21, 1:18 PM CDT | Mesoscale Discussion | SPC | Bandera, Bosque, Burnet, Coryell, Erath, Gillespie and 12 more | 117 min |
| May 21, 1:45 PM CDT | Severe Thunderstorm Watch | SPC | Bandera, Bell, Blanco, Bosque, Burnet, Comal and 29 more | 7 hr |
| May 21, 3:53 PM CDT | Mesoscale Discussion | SPC | Bosque, Burnet, Coryell, Dallas, Ellis, Gillespie and 9 more | 67 min |
Nearby
Mesoscale Discussions in Texas, 2011Mesoscale Discussions in Oklahoma, 2011Every 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.