Alert archive / Texas / Mesoscale Discussions in 2021
Mesoscale Discussion 2011
The Storm Prediction Center issued this mesoscale discussion at Dec 11, 2021, 1:36 AM CST for 10 parishes in Louisiana; 29 counties in Texas. It was in force for 114 min.
The area
The outline as issued.
The facts
- Issued
- Dec 11, 2021, 1:36 AM CST (07:36 UTC)
- Expired
- Dec 11, 2021, 3:30 AM CST
- In force
- 114 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
All 39 counties
Beauregard Parish, LA, Caldwell Parish, LA, De Soto Parish, LA, Grant Parish, LA, LaSalle Parish, LA, Natchitoches Parish, LA, Red River Parish, LA, Sabine Parish, LA, Vernon Parish, LA, Winn Parish, LA, Angelina County, TX, Austin County, TX, Brazos County, TX, Burleson County, TX, Cherokee County, TX, Colorado County, TX, Fayette County, TX, Fort Bend County, TX, Grimes County, TX, Hardin County, TX, Harris County, TX, Houston County, TX, Jasper County, TX, Lee County, TX, Liberty County, TX, Madison County, TX, Montgomery County, TX, Nacogdoches County, TX, Newton County, TX, Polk County, TX, Sabine County, TX, San Augustine County, TX, San Jacinto County, TX, Shelby County, TX, Trinity County, TX, Tyler County, TX, Walker County, TX, Waller County, TX, Washington County, TX
The radar
The Ft Polk radar (KPOE), 124 km from the middle of the area, began a volume at 07:36 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, 7.6 hours before the alert went out and 136 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
- 2052 J/kg
- Mixed-layer CIN
- 0 J/kg
- Mixed-layer LCL
- 482 m above ground
- 0-6 km bulk shear
- 48 kt
- 0-1 km storm-relative helicity
- 196 m²/s²
- 0-3 km storm-relative helicity
- 209 m²/s²
- Significant tornado parameter
- 2.7
- Supercell composite
- 10.1
The text
As transmitted.
827
ACUS11 KWNS 110736
SWOMCD
SPC MCD 110736
LAZ000-TXZ000-110930-
Mesoscale Discussion 2011
NWS Storm Prediction Center Norman OK
0136 AM CST Sat Dec 11 2021
Areas affected...portions of eastern Texas into central Louisiana
Concerning...Severe potential...Watch possible
Valid 110736Z - 110930Z
Probability of Watch Issuance...40 percent
SUMMARY...A line of strong to potentially severe thunderstorms is
expected to progress east over the next few hours. Damaging gusts
and perhaps an instance or two of marginally severe hail are
possible and a brief tornado cannot be completely ruled out.
Convective trends will continue to be monitored for the need of a WW
issuance.
DISCUSSION...An organized line of strong thunderstorms has developed
across eastern Texas within the axis of stronger instability (up to
2000 J/kg MLCAPE driven by 70+ F surface dewpoints). While linear
forcing and weak CINH have supported organized thunderstorm
development ahead of the cold front, overall deep-layer ascent is
relatively weak compared to the OH/TN Valley areas. Nonetheless, 07Z
mesoanalysis shows 60+ kts of effective bulk shear. The favorable
kinematics are driven primarily by deep-layer speed shear, with only
modest low-level hodograph curvature depicted by the 0709Z POE VWP
and some of the 06Z RAP forecast soundings.
Some of the stronger storms in the line may support a few damaging
gusts and perhaps an instance or two of marginally severe hail given
adequate buoyancy/deep-layer shear. While the low-level directional
shear is modest, very strong low-level speed shear is contributing
to 200+ m2/s3 effective SRH, so a brief tornado or two may still
occur. As such, convective trends will continue to be monitored for
the need of a WW issuance.
..Squitieri/Edwards.. 12/11/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...JAN...LCH...SHV...HGX...FWD...EWX...
LAT...LON 29859761 31959509 32239400 32219275 32119204 31969195
31639219 31089274 30479358 29989433 29479516 29419626
29859761SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Dec 10, 10:00 PM CST | Mesoscale Discussion | SPC | Bienville, Bossier, Caddo, Caldwell, Claiborne, De Soto and 16 more | 90 min |
| Dec 10, 10:44 PM CST | Tornado Watch | SPC | Bienville, Bossier, Caddo, Claiborne, Jackson, Lincoln and 4 more | 6 hr |
| Dec 11, 2:00 AM CST | Mesoscale Discussion | SPC | Bienville, Bossier, Claiborne, Lincoln, Morehouse, Ouachita and 3 more | 90 min |
| Dec 11, 4:02 AM CST | Mesoscale Discussion | SPC | Allen, Avoyelles, Beauregard, Calcasieu, Caldwell, Catahoula and 9 more | 118 min |
| Dec 10, 6:34 PM CST | Tornado Watch | SPC | Bowie, Camp, Cass, Franklin, Marion, Morris and 4 more | 4 hr |
Nearby
Mesoscale Discussions in Texas, 2021Mesoscale Discussions in Louisiana, 2021Every mesoscale discussion in 2021
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.