Erosion aloft of a ridge of high pressure centered west of the region reduced subsidence and increased buoyancy. That increased lift combined with mid level drying created an environment conducive for supercell development.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS LIX wrote it up.
Erosion aloft of a ridge of high pressure centered west of the region reduced subsidence and increased buoyancy. That increased lift combined with mid level drying created an environment conducive for supercell development.
The local office's own words before the first event, 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 the first event at Aug 15, 2:52 AM CST, 7 hours 55 minutes earlier.
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. &&
The national radar mosaic for the moment the first event began.
1 thunderstorm wind. Local standard time, as filed.
Several trees were knocked down by damaging thundrstorm winds on 24th street and Northwest Avenue.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Mississippi in 2020Every state in 2020This day in weather historyWarnings in Mississippi, August 2020
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 916049.