Alert archive / Louisiana / Mesoscale Discussions in 2021
Mesoscale Discussion 599
The Storm Prediction Center issued this mesoscale discussion at May 11, 2021, 8:33 PM CDT for 18 parishes in Louisiana; Jefferson County, Orange County, Texas. It was in force for 87 min.
The area
The outline as issued.
The facts
- Issued
- May 11, 2021, 8:33 PM CDT (01:33 UTC)
- Expired
- May 11, 2021, 10:00 PM CDT
- In force
- 87 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 166
Counties Acadia Parish, LA, Allen Parish, LA, Ascension Parish, LA, Assumption Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Cameron Parish, LA, Evangeline Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Jefferson Davis Parish, LA, Lafayette Parish, LA, Saint James Parish, LA, Saint Landry Parish, LA, Saint Martin Parish, LA, St. Mary Parish, LA, Vermilion Parish, LA, West Baton Rouge Parish, LA, Jefferson County, TX, Orange County, TX
The radar
The Lake Charles radar (KLCH), 58 km from the middle of the area, began a volume at 01:37 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, 1.6 hours before the alert went out and 56 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
- 2262 J/kg
- Mixed-layer CIN
- -1 J/kg
- Mixed-layer LCL
- 759 m above ground
- 0-6 km bulk shear
- 33 kt
- 0-1 km storm-relative helicity
- 53 m²/s²
- 0-3 km storm-relative helicity
- 131 m²/s²
- Significant tornado parameter
- 1.8
- Supercell composite
- 12.5
The text
As transmitted.
913
ACUS11 KWNS 120134
SWOMCD
SPC MCD 120133
LAZ000-TXZ000-120300-
Mesoscale Discussion 0599
NWS Storm Prediction Center Norman OK
0833 PM CDT Tue May 11 2021
Areas affected...Southern Louisiana and far southeast Texas
Concerning...Severe Thunderstorm Watch 166...
Valid 120133Z - 120300Z
The severe weather threat for Severe Thunderstorm Watch 166
continues.
SUMMARY...An isolated severe weather threat will continue overnight.
Isolated damaging wind will be the primary threat.
DISCUSSION...Widespread storms have developed across southern
Louisiana along an instability gradient with a very moist low-level
airmass being transported northward into the region. The 00Z KLCH
RAOB sampled this rich low-level environment well with a mean mixing
ratio of 16.5 g/kg. This low-level moisture provides a broad
reservoir of unstable air with MUCAPE in excess of 3000 J/kg per 00Z
KLCH RAOB. This moist airmass has limited the ability for cold pool
development and thus the line of storms entering western Louisiana
has struggled to accelerate eastward and produce much wind damage.
The expansive storm development has limited discrete development and
the potential for severe hail, especially given the tropical airmass
present in the region. Therefore, expect widespread storms to
continue overnight, but expect the severe threat to be muted with
water-loaded downdrafts the primary mechanism for isolated damaging
wind gusts. Therefore, no downstream watch is anticipated at this
time.
..Bentley/Hart.. 05/12/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LIX...LCH...HGX...
LAT...LON 30159447 30859365 30829212 30269056 29749043 29559064
29409129 29499217 29689306 29729345 29629399 29519438
30159447SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 11, 8:02 PM CDT | Mesoscale Discussion | SPC | Brooks, Cameron, Duval, Hidalgo, Jim Hogg, Jim Wells and 8 more | 118 min |
| May 11, 8:34 PM CDT | Severe Thunderstorm Watch | SPC | Brooks, Cameron, Hidalgo, Jim Hogg, Kenedy, Kleberg and 5 more | 7 hr |
| May 11, 10:47 PM CDT | Mesoscale Discussion | SPC | Brooks, Cameron, Duval, Hidalgo, Jim Hogg, Jim Wells and 8 more | 118 min |
| May 12, 1:41 AM CDT | Mesoscale Discussion | SPC | Cameron | 94 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.