A weak mid-level trough and convergence along lingering small scale boundaries from previous convection led to a severe thunderstorm across Southeast South Carolina.
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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 CHS wrote it up.
A weak mid-level trough and convergence along lingering small scale boundaries from previous convection led to a severe thunderstorm across Southeast South Carolina.
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 Charleston, SC wrote its last area forecast discussion before the first event at Aug 12, 6:44 PM EST, 11 minutes earlier.
Area Forecast Discussion National Weather Service Charleston SC 744 PM EDT Wed Aug 12 2020 .SYNOPSIS... A trough of low pressure will persist inland, while high pressure remains over the Atlantic through late week. A weak cold front could approach the region over the weekend and linger in the vicinity into early next week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Early this evening: Convection in the late afternoon was marked by a rather chaotic network of outflow boundaries. The latest radar imagery indicates that we may finally have a dominant outflow boundary that is currently generating a line of thunderstorms that runs up the Georgia coast and into Beaufort, Jasper, and Colleton counties. This outflow boundary should continue to progress eastward and could kick off some late evening thunderstorm activity across the Charleston metro. The good news is that updrafts are relatively tame, with 50+ dBZ reflectivity struggling to even get above 20 kft. The main concern is for some locally heavy rainfall. Later in the overnight, most of the convection should be across the coastal waters and the rain chances reflect that. Like last night, no significant fog or stratus concerns. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/... A weak upper trough will remain positioned over the eastern United States through Saturday while at the surface Atlantic high pressure remains offshore. An unseasonably moist airmass will linger with Precipitable Water values in excess of 2". Fairly good coverage of showers and tstms is expected through the period, particularly from late morning through early evening. However, due to the upper trough overhead, convection could initiate any time of day so we maintained chance PoPs through the overnight hours as well. Daytime highs will range from 89 to 93 degrees with max heat indices 100-105F. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... A weak front will stall over or near the region through early next week. Aloft, a shortwave trough over the Southeast will get absorbed in a larger scale trough becoming more amplified over the eastern half of the country. Vort energy and forcing from the surface boundary and afternoon sea breeze will support mention of showers and thunderstorms in the forecast each day. Coverage will be dependent on where the boundary is located, so for now have kept rain chances below 50% as there are still discrepancies between model solutions. Temperatures will be near climo. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... At KCHS: An outflow boundary is moving eastward toward the area and could kick off shower and thunderstorm activity later this evening. For now, the TAF just carries VCTS but we will amend as radar trends become more clear. Later tonight convection should end and become confined to the adjacent coastal waters. Can't rule out a shower or thunderstorm late, but confidence is too low to include. Another round of showers and thunderstorms will develop Thursday afternoon. At KSAV: Thunderstorms have moved through the terminal and we will initialize with residual rainfall that could last for an hour or so. VFR conditions should return and then prevail through the night. Another round of showers and thunderstorms will develop Thursday afternoon. Extended Aviation Outlook: Flight restrictions possible in showers/thunderstorms each day, mainly in the afternoon/evening. && .MARINE... Today and tonight: A broad trough will persist inland over the Southeast, as the Atlantic ridge holds in place nearby to our south and east. Sea breeze influences, plus the nocturnal low level jet will allow for SW winds around 10 to 15kt, while seas will hold at 2 to 3 ft. Mariners are advised that a few of the t-storms that occur will produce gusty winds, frequent lightning strikes and heavy rains reducing visibilities to near zero at times. Atlantic high pressure will remain in place through the weekend, maintaining modest south to southwest flow across the marine area. Outside of occasional showers/thunderstorms, no marine concerns are anticipated as winds stay 15 knots or less and seas no higher than 3 feet. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && NEAR TERM...BSH SHORT TERM...JRL LONG TERM...ETM AVIATION...BSH/JRL MARINE...BRM/JRL
Hazardous Weather Outlook National Weather Service Charleston SC 352 AM EDT Wed Aug 12 2020 AMZ330-350-352-354-374-GAZ087-088-099>101-114>119-137>141-SCZ040- 042>045-047>052-130800- Charleston Harbor- Waters from South Santee River to Edisto Beach SC out 20 NM- Waters from Edisto Beach SC to Savannah GA out 20 NM- Waters from Savannah GA to Altamaha Sound GA out 20 NM, including Grays Reef National Marine Sanctuary- Waters from Savannah GA to Altamaha Sound GA from 20 to 60 NM- Jenkins-Screven-Candler-Bulloch-Effingham-Tattnall-Evans- Inland Bryan-Coastal Bryan-Inland Chatham-Coastal Chatham-Long- Inland Liberty-Coastal Liberty-Inland McIntosh-Coastal McIntosh- Allendale-Hampton-Inland Colleton-Dorchester-Inland Berkeley- Inland Jasper-Beaufort-Coastal Colleton-Charleston-Coastal Jasper- Tidal Berkeley- 352 AM EDT Wed Aug 12 2020 This Hazardous Weather Outlook is for Atlantic coastal waters, southeast Georgia and southeast South Carolina. .DAY ONE...Today and tonight. The probability for widespread hazardous weather is low. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday. The probability for widespread hazardous weather is low. .SPOTTER INFORMATION STATEMENT... Spotter assistance is not anticipated at this time.
Special Weather Statement
National Weather Service Charleston SC
600 PM EDT Wed Aug 12 2020
GAZ088-122230-
Screven-
600 PM EDT Wed Aug 12 2020
...STRONG THUNDERSTORMS WILL IMPACT PORTIONS OF SCREVEN COUNTY...
At 600 PM EDT, National Weather Service doppler radar indicated a
strong thunderstorm over Hunters, or 9 miles southeast of Sylvania.
This storm was nearly stationary.
HAZARD...strong winds 45 to 55 mph.
IMPACT...Expect minor damage to tree limbs and blowing around of
light, unsecured objects.
Some locations in the path of this storm include...
Newington, Captolo and Hunters.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Torrential rainfall is also occurring with this storm and may lead to
flooding of low lying and poor drainage areas. Do not drive your
vehicle through flooded roadways.
Report damage directly to the Charleston National Weather Service at
1-888-383-2024 when it is safe to do so. You can also email your
report to nws.charlestonsc@noaa.gov.
&&
LAT...LON 3274 8158 3270 8143 3269 8141 3265 8140
3263 8141 3263 8142 3262 8141 3257 8143
3255 8147 3258 8167
TIME...MOT...LOC 2200Z 016DEG 4KT 3265 8151Special Weather Statement
National Weather Service Charleston SC
604 PM EDT Wed Aug 12 2020
GAZ101-116-118-122230-
Effingham-Inland Chatham-Inland Bryan-
604 PM EDT Wed Aug 12 2020
...STRONG THUNDERSTORMS WILL IMPACT PORTIONS OF BRYAN...EFFINGHAM AND
CHATHAM COUNTIES...
At 604 PM EDT, National Weather Service doppler radar indicated a
strong thunderstorm over Bloomingdale, or over Pooler. This storm was
nearly stationary.
HAZARD...strong winds 45 to 55 mph.
IMPACT...Expect minor damage to tree limbs and blowing around of
light, unsecured objects.
Some locations in the path of this storm include...
Pooler, Richmond Hill, I-16/I-95 Interchange, Savannah International
Airport, Godley Station, Port Wentworth, Bloomingdale and Meldrim.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Report damage directly to the Charleston National Weather Service at
1-888-383-2024 when it is safe to do so. You can also email your
report to nws.charlestonsc@noaa.gov.
&&
LAT...LON 3216 8143 3217 8119 3195 8128 3194 8143
3195 8146 3197 8148 3196 8149 3197 8151
3196 8152 3197 8153
TIME...MOT...LOC 2204Z 040DEG 4KT 3211 8130PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHARLESTON SC
727 PM EDT WED AUG 12 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0724 PM HEAVY RAIN 1 NW POOLER 32.12N 81.25W
08/12/2020 M2.15 INCH CHATHAM GA COCORAHS
REPORT RELAYED BY COCORAHS OBSERVER GA-CT-1.
&&
EVENT NUMBER CHS2000621The Charleston,SC radar (KCLX), 69 km away, was scanning. The volume nearest the first event began at 23:55 UTC.
1 thunderstorm wind. Local standard time, as filed.
A Beaufort County emergency manager reported a tree down on a home near Alexandra Loop.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in South Carolina in 2020Every state in 2020This day in weather historyWarnings in South Carolina, 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: 917656.