Alert archive / Louisiana / Mesoscale Discussions in 2021
Mesoscale Discussion 1742
The Storm Prediction Center issued this mesoscale discussion at Sep 14, 2021, 12:41 AM CDT for Cameron Parish, Louisiana; Jefferson County, Texas. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Sep 14, 2021, 12:41 AM CDT (05:41 UTC)
- Expired
- Sep 14, 2021, 3:15 AM CDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
Counties Cameron Parish, LA, Jefferson County, TX
The radar
The Lake Charles radar (KLCH), 92 km from the middle of the area, began a volume at 05:42 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, 5.7 hours before the alert went out and 92 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
- 528 J/kg
- Mixed-layer CIN
- -3 J/kg
- Mixed-layer LCL
- 794 m above ground
- 0-6 km bulk shear
- 30 kt
- 0-1 km storm-relative helicity
- 53 m²/s²
- 0-3 km storm-relative helicity
- 327 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 2.3
The text
As transmitted.
853
ACUS11 KWNS 140541
SWOMCD
SPC MCD 140541
LAZ000-TXZ000-140815-
Mesoscale Discussion 1742
NWS Storm Prediction Center Norman OK
1241 AM CDT Tue Sep 14 2021
Areas affected...Upper Coast of TX...far southwest LA
Concerning...Severe potential...Watch unlikely
Valid 140541Z - 140815Z
Probability of Watch Issuance...20 percent
SUMMARY...Weak/transient mini supercells are possible overnight near
the immediate coast of adjacent parts of the TX/LA coast. A
weak/brief tornado cannot be ruled out, but the overall magnitude
and coverage of the risk will likely preclude a tornado watch
issuance overnight.
DISCUSSION...Hurricane Nicholas is near the TX coast with several
convective bands embedded within a heavy rain shield per radar
mosaic imagery. KHGX and KLCH 88D VAD show enlarged hodographs
conditionally supporting mesocyclone development. Surface
temperatures have warmed into the upper 70s to near 80 deg F during
the past couple of hours near the mouth of the Sabine River and
dewpoints are currently in the upper 70s. It appears a narrow
tongue of modest buoyancy has begun to infiltrate the immediate
coast near the TX/LA border with around 250 J/kg MLCAPE according to
modified RAP forecast soundings. Given the weak buoyancy/strong SRH
setup, occasional mini supercell development within the rain shield
is expected to continue near the TX/LA border for at least the next
several hours. Accompanying the strongest circulations could be a
weak/brief tornado. However, the overall expected magnitude of the
tornado risk and associated coverage, will probably preclude a
tornado watch issuance. Convective trends will continue to be
monitored.
..Smith/Guyer.. 09/14/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LCH...HGX...
LAT...LON 29569439 29889425 30029319 29579222 28609229 28759333
28739399 29569439SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 14, 12:32 PM CDT | Mesoscale Discussion | SPC | Orleans, Saint Bernard, Saint Tammany | 88 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.