Alert archive / Louisiana / Severe Thunderstorm Warnings in 2020

Severe Thunderstorm Warning 104, NWS New Orleans, LA

August 15, 2020Orleans Parish, Saint Bernard Parish, Saint Tammany Parish, Louisiana; Hancock County, Mississippi

NWS New Orleans, LA issued this severe thunderstorm warning at Aug 15, 2020, 2:23 PM CDT for Orleans Parish, Saint Bernard Parish, Saint Tammany Parish, Louisiana; Hancock County, Mississippi. It was in force for 37 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued
Aug 15, 2020, 2:23 PM CDT (19:23 UTC)
Expired
Aug 15, 2020, 3:00 PM CDT
In force
37 min
Issued by
NWS New Orleans, LA
Area
Storm-based polygon
Hail
0.75 in
Wind
60.0 mph

Counties Orleans Parish, LA, Saint Bernard Parish, LA, Saint Tammany Parish, LA, Hancock County, MS

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 12:00Z, 7.4 hours before the alert went out and 12 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-pSkew-T log-p diagram, Slidell Radar S, LA at 12:00Z on 2020-08-15Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 3292 joules per kilogram.LCLEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Slidell Radar S, LA at 12:00Z on 2020-08-15The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 22 square meters per square second.1939Sfc1 km3 km6 km9 kmRMLM
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
3292 J/kg
Mixed-layer CIN
-3 J/kg
Mixed-layer LCL
622 m above ground
0-6 km bulk shear
19 kt
0-1 km storm-relative helicity
22 m²/s²
0-3 km storm-relative helicity
77 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS New Orleans, LA wrote its last area forecast discussion before this severe thunderstorm warning went out at Aug 15, 3:52 AM CDT, 10 hours 31 minutes earlier.

Area forecast discussion, Aug 15, 3:52 AM CDT, 10 hours 31 minutes before
Area Forecast Discussion
National Weather Service New Orleans LA
352 AM CDT Sat Aug 15 2020

.SYNOPSIS...

Weak upper trough remains across the area with a rather wet
airmass. Precipitable water on the 00z LIX sounding was at 2.17
inches. The tail of a weak shortwave over Alabama was triggering
isolated convection from Natchez southeastward to Mobile, clipping
the northern counties of our area. In addition, a few
showers/storms over the lower portions of the Louisiana coastal
parishes. Early morning temperatures generally in the mid and
upper 70s across the area.

&&

.SHORT TERM...

Earlier forecast expectations remain reasonable. Scattered
convection this morning across the area, then as low level winds
become more northwesterly during the day, the column begins to dry
out. By 00z this evening, GFSBufr sounding for New Orleans shows
precipitable water values dropping from the aforementioned 2+
inches to 1.6 inches. Beyond tonight, moisture levels remain
unseasonably low into the early part of the workweek, generally
well below 1.5 inches. Expect at that point, little or no
convection should develop over land on Sunday. Any convection
Monday will be very isolated and limited to sea breeze boundaries.
Very tempted to go with a completely dry forecast beyond this
afternoon through Monday.

Will continue forecast trends of high temperatures at the upper
end of the guidance envelope. One thing to watch for on Sunday,
and probably Monday, is if north winds are strong enough, say near
10 mph, to cancel out the sea breeze, high temperatures could get
above forecast expectations along the Mississippi coast and north
of Interstate 12.

&&

.LONG TERM...

Low level winds remain offshore through at least Wednesday, and
even after that, moisture levels as measured by precipitable water
values doesn't return to 1.75 inches until Thursday night or
Friday. Don't see any indications of any organized convective
threat through the end of the week, but as moisture levels slowly
increase, could see a little more convection near lake/sea breeze
boundaries during the afternoon hours. Will continue trend of
using the upper end of the guidance envelope for high temperature
forecasts.

&&

.AVIATION...

Seeing a few MVFR ceilings this morning at KASD and KHUM. Can't
rule out a convective threat at KMCB and KGPT prior to the 12z
forecast issuance, and will handle those with amendments if
necessary. HRRR/RAP solutions don't really pick up on much in the
way of TSRA until well beyond 18z, closer to 20-21z, so may push
back initiation of VCTS a couple of hours to fit this. Once
convective threat diminishes beyond sunset, don't expect much in
the way of flight restrictions the rest of the weekend.

&&

.MARINE...

Outside of the threat of thunderstorms, particularly today, no
marine issues anticipated. Winds should remain below 15 knots
outside of thunderstorms through the period.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  92  74  94  73 /  30   0  10   0
BTR  94  75  97  75 /  30   0  10  10
ASD  93  74  97  74 /  30  10  10   0
MSY  93  78  95  79 /  30  10  10  10
GPT  91  76  94  76 /  40  10  10  10
PQL  93  74  97  74 /  40  10  10  10

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...None.
MS...None.
GM...None.
&&

In the hours before

Local storm report, Aug 15, 12:48 PM CDT, 1 hour 35 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NEW ORLEANS LA
1248 PM CDT SAT AUG 15 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1147 AM     TSTM WND DMG     MCCOMB                  31.25N 90.47W
08/15/2020                   PIKE               MS   LAW ENFORCEMENT

            TREES WERE KNOCKED DOWN BY DAMAGING THUNDERSTORM WINDS ON
            24TH STREET AND NORTHWEST AVENUE.

&&

MEFFERSO
Special weather statement, Aug 15, 1:14 PM CDT, 1 hour 9 minutes before
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Special weather statement, Aug 15, 1:29 PM CDT, 54 minutes before
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Special weather statement, Aug 15, 2:03 PM CDT, 20 minutes before
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Special weather statement, Aug 15, 2:16 PM CDT, 7 minutes before
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The office that day

Everything else NWS New Orleans, LA issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 14, 7:15 PM CDTSpecial Marine WarningLIX30 min
Aug 15, 3:23 AM CDTSpecial Marine WarningLIX22 min
Aug 15, 5:36 AM CDTSpecial Marine WarningLIX52 min
Aug 15, 12:20 PM CDTSpecial Weather StatementLIXWashington40 min
Aug 15, 12:50 PM CDTSevere Thunderstorm WarningLIXSaint Tammany25 min
Aug 15, 12:53 PM CDTSevere Thunderstorm WarningLIXWashington37 min
Aug 15, 1:26 PM CDTSpecial Marine WarningLIX64 min
Aug 15, 1:29 PM CDTSpecial Weather StatementLIXSaint Tammany31 min
Aug 15, 1:52 PM CDTSevere Thunderstorm WarningLIXSaint Tammany23 min
Aug 15, 2:08 PM CDTSpecial Marine WarningLIX67 min
Aug 15, 2:16 PM CDTSpecial Weather StatementLIXSaint Tammany29 min
Aug 15, 2:22 PM CDTSpecial Marine WarningLIX68 min
Aug 15, 2:43 PM CDTSpecial Weather StatementLIXTangipahoa32 min
Aug 15, 2:57 PM CDTSpecial Marine WarningLIX33 min
Aug 15, 3:00 PM CDTSpecial Marine WarningLIX60 min
Aug 15, 3:26 PM CDTSpecial Weather StatementLIXLivingston34 min
Aug 15, 3:28 PM CDTSpecial Weather StatementLIXSaint Helena47 min
Aug 15, 3:36 PM CDTSpecial Weather StatementLIXOrleans39 min
Aug 15, 3:40 PM CDTSpecial Marine WarningLIX65 min
Aug 15, 3:50 PM CDTSpecial Weather StatementLIXSaint Charles40 min
Aug 15, 3:53 PM CDTSpecial Weather StatementLIXLivingston37 min
Aug 15, 4:06 PM CDTSpecial Weather StatementLIXLivingston24 min
Aug 15, 4:11 PM CDTSpecial Weather StatementLIXJefferson, Plaquemines34 min
Aug 15, 4:15 PM CDTSpecial Weather StatementLIXEast Baton Rouge, East Feliciana, Saint Helena45 min
Aug 15, 4:47 PM CDTSpecial Marine WarningLIX58 min
Aug 15, 4:49 PM CDTSpecial Marine WarningLIX56 min
Aug 15, 5:12 PM CDTSpecial Weather StatementLIXEast Baton Rouge48 min
Aug 15, 5:18 PM CDTSpecial Weather StatementLIXJefferson, Lafourche42 min
Aug 15, 5:47 PM CDTSpecial Weather StatementLIXPointe Coupee43 min
Aug 15, 2:53 AM CDTSpecial Weather StatementLIXJackson67 min
Aug 15, 12:13 PM CDTSpecial Weather StatementLIXPearl River32 min
Aug 15, 12:57 PM CDTSevere Thunderstorm WarningLIXHancock, Harrison33 min
Aug 15, 1:14 PM CDTSpecial Weather StatementLIXHancock31 min
Aug 15, 1:25 PM CDTSpecial Weather StatementLIXHancock20 min
Aug 15, 2:03 PM CDTSpecial Weather StatementLIXHarrison27 min

Nearby

Severe Thunderstorm Warnings in Louisiana, 2020Severe Thunderstorm Warnings in Mississippi, 2020Every severe thunderstorm warning in 2020

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.