Alert archive / Louisiana / Mesoscale Discussions in 2021
Mesoscale Discussion 691
The Storm Prediction Center issued this mesoscale discussion at May 19, 2021, 11:34 PM CDT for 11 parishes in Louisiana. It was in force for 86 min.
The area
The outline as issued.
The facts
- Issued
- May 19, 2021, 11:34 PM CDT (04:34 UTC)
- Expired
- May 20, 2021, 1:00 AM CDT
- In force
- 86 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 5%
Counties Acadia Parish, LA, Assumption Parish, LA, Cameron Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Jefferson Davis Parish, LA, Lafayette Parish, LA, Saint Martin Parish, LA, St. Mary Parish, LA, Terrebonne Parish, LA, Vermilion Parish, LA
The radar
The Lake Charles radar (KLCH), 113 km from the middle of the area, began a volume at 04:39 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, 4.6 hours before the alert went out and 111 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
- 708 J/kg
- Mixed-layer CIN
- -6 J/kg
- Mixed-layer LCL
- 567 m above ground
- 0-6 km bulk shear
- 30 kt
- 0-1 km storm-relative helicity
- 217 m²/s²
- 0-3 km storm-relative helicity
- 218 m²/s²
- Significant tornado parameter
- 0.5
- Supercell composite
- 4.8
The text
As transmitted.
193
ACUS11 KWNS 200434
SWOMCD
SPC MCD 200434
LAZ000-200600-
Mesoscale Discussion 0691
NWS Storm Prediction Center Norman OK
1134 PM CDT Wed May 19 2021
Areas affected...coastal areas of southwest and south-central
Louisiana
Concerning...Severe potential...Watch unlikely
Valid 200434Z - 200600Z
Probability of Watch Issuance...5 percent
SUMMARY...Strong, gusty thunderstorm winds are possible along
coastal areas of southwest and south-central Louisiana over the next
few hours. A watch is currently not expected.
DISCUSSION...A linear mesoscale convective system (MCS) is
organizing across the northwest Gulf of Mexico and southwest
Louisiana to the northeast of a remnant mesoscale convective vortex
(MCV) across the northwest Gulf of Mexico. Recent radar and
lightning trends have indicated an increase in thunderstorm
intensity with an associated increase in thunderstorm outflow winds.
Given that these thunderstorms are associated with an MCV and moving
into a background environment that is very moist and unstable and
weakly capped, they should continue to persist overnight as they
move east.
Low-to-mid-level wind profiles are largely southerly across the
region per area VADS. Despite resulting in modest effective-layer
shear, this wind profile will augment thunderstorm outflow winds
with any northward moving convection. In this scenario, a localized
wind threat may materialize with the strongest thunderstorm cores.
Given the orientation of the MCS, this threat would materialized
mostly along coastal areas of southwest and south-central Louisiana,
where thunderstorm winds will also be slightly higher owing to less
surface friction ove the Gulf of Mexico. The threat should remain
fairly brief/localized and a watch is currently not anticipated.
..Marsh/Dial.. 05/20/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LIX...LCH...
LAT...LON 29669321 30109334 30379309 30359199 30279124 29959074
29409070 29089096 29119164 29289259 29449302 29669321Nearby
Mesoscale 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.