Alert archive / Louisiana / Mesoscale Discussions in 2021
Mesoscale Discussion 1911
The Storm Prediction Center issued this mesoscale discussion at Oct 27, 2021, 7:36 AM CDT for 10 parishes in Louisiana; 7 counties in Texas. It was in force for 84 min.
The area
The outline as issued.
The facts
- Issued
- Oct 27, 2021, 7:36 AM CDT (12:36 UTC)
- Expired
- Oct 27, 2021, 9:00 AM CDT
- In force
- 84 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch likely
- Chance of a watch
- 80%
Counties Acadia Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Cameron Parish, LA, Iberia Parish, LA, Jefferson Davis Parish, LA, Lafayette Parish, LA, St. Mary Parish, LA, Terrebonne Parish, LA, Vermilion Parish, LA, Chambers County, TX, Hardin County, TX, Jasper County, TX, Jefferson County, TX, Newton County, TX, Orange County, TX, Tyler County, TX
The radar
The Lake Charles radar (KLCH), 19 km from the middle of the area, began a volume at 12:38 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
Lake Charles Mun, LA (KLCH), launched 12:00Z, 0.6 hours before the alert went out and 18 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
- 1422 J/kg
- Mixed-layer CIN
- -5 J/kg
- Mixed-layer LCL
- 604 m above ground
- 0-6 km bulk shear
- 38 kt
- 0-1 km storm-relative helicity
- 160 m²/s²
- 0-3 km storm-relative helicity
- 255 m²/s²
- Significant tornado parameter
- 1.1
- Supercell composite
- 7.1
The text
As transmitted.
750
ACUS11 KWNS 271236
SWOMCD
SPC MCD 271236
LAZ000-TXZ000-271400-
Mesoscale Discussion 1911
NWS Storm Prediction Center Norman OK
0736 AM CDT Wed Oct 27 2021
Areas affected...Parts of the upper Texas and Louisiana coast
vicinity
Concerning...Severe potential...Watch likely
Valid 271236Z - 271400Z
Probability of Watch Issuance...80 percent
SUMMARY...Discrete thunderstorm development is ongoing and likely to
continue across the region into mid morning. It appears that this
will include the evolution of a few supercell structures which may
begin to pose a risk for tornadoes.
DISCUSSION...Thunderstorm activity on the leading edge of the
southeastward advancing, convectively generated surface cold pool
has yet to show signs of appreciable intensification, and the window
of opportunity for this to occur appears to be narrowing, with it on
track to reach mid/upper Texas coastal areas by or shortly after
15Z. However, this activity is now preceded by scattered discrete
thunderstorm development, likely rooted within the seasonably moist
and moderately unstable boundary layer, near upper Texas and
southwestern Louisiana coastal areas. These storms probably have
been supported by forcing associated with weak low-level warm
advection, with at least one cell with a sustained low-level
mesocyclone offshore east of Galveston.
The isolated supercell may advance inland across coastal areas
southwest of Beaumont/Port Arthur during the next hour or two, and
similar additional development near coastal areas appears at least
possible through 14-15Z. Although cloud cover may slow
boundary-layer destabilization inland across southwestern into south
central Louisiana coastal areas, strengthening of southerly 850 mb
flow (in excess of 30 kt) is ongoing, and will contribute to
enlarging clockwise curved low-level hodographs.
..Kerr/Guyer.. 10/27/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LIX...LCH...HGX...
LAT...LON 30799463 30949382 30489287 30149168 29779078 29089063
28969144 29269316 29269464 29839501 30189475 30799463SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Oct 27, 7:55 AM CDT | Tornado Watch | SPC | Acadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 13 more | 9 hr |
| Oct 27, 9:44 AM CDT | Mesoscale Discussion | SPC | Bienville, Bossier, Caddo, Caldwell, Claiborne, De Soto and 7 more | 2 hr |
| Oct 27, 10:08 AM CDT | Tornado Watch | SPC | Bienville, Bossier, Caddo, Caldwell, Claiborne, De Soto and 6 more | 5 hr |
| Oct 27, 10:59 AM CDT | Mesoscale Discussion | SPC | Beauregard, Vernon | 91 min |
| Oct 27, 12:50 PM CDT | Mesoscale Discussion | SPC | Acadia, Ascension, Assumption, Avoyelles, Concordia, East Baton Rouge and 24 more | 85 min |
| Oct 27, 12:52 PM CDT | Mesoscale Discussion | SPC | Bienville, Bossier, Caddo, Caldwell, Claiborne, De Soto and 7 more | 83 min |
| Oct 27, 1:53 PM CDT | Tornado Watch | SPC | Ascension, Assumption, Catahoula, Concordia, East Baton Rouge, East Feliciana and 18 more | 8 hr |
| Oct 27, 3:25 PM CDT | Mesoscale Discussion | SPC | Ascension, Assumption, East Baton Rouge, East Feliciana, Iberville, Jefferson and 13 more | 95 min |
| Oct 27, 5:13 PM CDT | Mesoscale Discussion | SPC | Orleans, Saint Bernard, Saint John the Baptist, Saint Tammany, Tangipahoa, Washington | 2 hr |
| Oct 26, 7:23 PM CDT | Severe Thunderstorm Watch | SPC | Archer, Baylor, Brown, Callahan, Clay, Coke and 45 more | 8 hr |
| Oct 26, 9:37 PM CDT | Mesoscale Discussion | SPC | Archer, Baylor, Callahan, Clay, Coke, Coleman and 26 more | 83 min |
| Oct 27, 1:32 AM CDT | Severe Thunderstorm Watch | SPC | Anderson, Bastrop, Bell, Bexar, Blanco, Bosque and 48 more | 6 hr |
| Oct 27, 1:59 AM CDT | Mesoscale Discussion | SPC | Collin, Cooke, Dallas, Denton, Ellis, Grayson and 8 more | 91 min |
| Oct 27, 5:13 AM CDT | Mesoscale Discussion | SPC | Atascosa, Austin, Bastrop, Bexar, Brazos, Burleson and 22 more | 2 hr |
| Oct 27, 9:08 AM CDT | Mesoscale Discussion | SPC | Hardin, Jasper, Jefferson, Newton, Orange, Tyler | 97 min |
Nearby
Mesoscale Discussions in Louisiana, 2021Mesoscale Discussions in Texas, 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.