Alert archive / Louisiana / Mesoscale Discussions in 2021

Mesoscale Discussion 852

June 4, 20215 parishes in Louisiana

The Storm Prediction Center issued this mesoscale discussion at Jun 4, 2021, 5:01 PM CDT for 5 parishes in Louisiana. It was in force for 89 min.

The area

The outline as issued.

The facts

Issued: Jun 4, 2021, 5:01 PM CDT (22:01 UTC)
Expired: Jun 4, 2021, 6:30 PM CDT
In force: 89 min
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 5%

Counties Allen Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Cameron Parish, LA, Jefferson Davis Parish, LA

The radar

The Lake Charles radar (KLCH), 10 km from the middle of the area, began a volume at 22:01 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 12:00Z, 10.0 hours before the alert went out and 9 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.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 242 J/kg
Mixed-layer CIN: -33 J/kg
Mixed-layer LCL: 749 m above ground
0-6 km bulk shear: 8 kt
0-1 km storm-relative helicity: 6 m²/s²
0-3 km storm-relative helicity: 24 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

690 
ACUS11 KWNS 042201
SWOMCD
SPC MCD 042201 
LAZ000-TXZ000-042330-

Mesoscale Discussion 0852
NWS Storm Prediction Center Norman OK
0501 PM CDT Fri Jun 04 2021

Areas affected...southwest Louisiana

Concerning...Severe potential...Watch unlikely 

Valid 042201Z - 042330Z

Probability of Watch Issuance...5 percent

SUMMARY...Thunderstorms this afternoon across southwest Louisiana
will pose a threat of brief tornadoes. The highly localized and
marginal nature of the threat should preclude the need for a watch.

DISCUSSION...Thunderstorms continue to develop across southwest
Louisiana within a very moist, unstable, and weakly capped airmass.
KLCH wind data suggests that weak mesolow may be developing across
Cameron parish, just north of Holly Beach. This mesolow/MCV should
maintain sufficient low-level convergence the next couple of hours
to sustain ongoing thunderstorms before a gradual weakening later
this evening with the loss of diurnal heating.

VAD data from KLCH shows small, but strongly looped low-level
hodographs which will support brief, transient low-level
circulations. This is borne out in KLCH radar imagery showing
several transient rotational velocity signatures within the broader
thunderstorm complex across southwest Louisiana. As such, a couple
of brief tornadoes cannot be ruled out this afternoon and evening.

The localized and marginal nature of the threat should preclude the
need for a watch.

..Marsh/Thompson.. 06/04/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...LCH...

LAT...LON   29739373 30309367 30769349 30719247 29959240 29599268
            29639308 29739373

Nearby

Mesoscale Discussions in Louisiana, 2021 Every 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.