| Above: Cathie Morris, right, tells Red Cross volunteer Laurie Howell on Tuesday, December 17, 2019 that her sister was killed by one of the April 2011 tornadoes, not far from what they're standing, in front of Morris' house, damaged by the Monday, December 16, 2019 storms off Neely Hill Loop in Limestone County, Ala. Image credit: Jeronimo Nisa/The Decatur Daily via AP. |
One of the most intense severe weather outbreaks of 2019 escalated quickly across Louisiana and Mississippi on Monday afternoon, then pushed eastward into Alabama, Georgia, and the Florida Panhandle. As of this writing, the NOAA/NWS Storm Prediction Center (SPC) had tallied 43 preliminary tornado reports for the period from 6 am CST Monday to 6 am Tuesday, December 16-17. Another tornado was reported Tuesday morning in south Georgia.
Update (December 18): At least 28 tornadoes have been confirmed from Monday and Tuesday, according to a compilation from Jonathan Erdman at weather.com. Seven of those were rated EF2 on the Enhanced Fujita Scale, and four were confirmed at EF3 strength.
This outbreak ramped up at surprising speed. Monday’s first tornado report came at 10:35 am CST, and the first storm-related fatality occurred less than an hour afterward, near Alexandria, Louisiana. A husband and wife were killed Monday evening in Town Creek, Alabama, and a fourth death occurred in high water in Greenup County, Kentucky, on Tuesday morning. More than a dozen people were injured in Mississippi alone, according to weather.com.
NWS Jackson is surveying the damage in Sumrall from yesterday’s tornado. pic.twitter.com/EdL0Uj7SlY
— Patrick Bigbie WDAM (@PatrickWDAM) December 17, 2019
Survey teams from several NWS offices assessed the far-flung damage on Tuesday, with additional surveys to come on Wednesday.
The NWS office in Lake Charles, Louisiana, found that an EF3 tornado tracked for 62 miles from near DeRidder to near Alexandria, with top winds of 140 to 160 mph.
The NWS office in Jackson, Mississippi, found that a long-lived supercell thunderstorm that moved from far southwest Mississippi into southwest Alabama produced. This storm also produced an EF3 tornado from Sumrall into far southern Covington County, northwest of Hattiesburg. The office also confirmed low-end EF3 damage from the same storm at Laurel in Jones County.
@NWSJacksonMS tornado in Foxworth,MS yesterday pic.twitter.com/BbxiEqcdlE
— Danny Hrapmann (@DHRAP) December 17, 2019
Farther downstream, the same supercell produced EF2 damage with winds estimated at 120 mph just west of Demopolis, Alabama, according to the NWS/Birmingham office. Additional tornado tracks may yet be analyzed from this long-lived supercell.
The Jackson office also found that an EF3 twister with top winds of 150 mph tracked for more than 18 miles across Simpson and Smith counties, just southeast of Jackson.
An EF1 tornado tracked 22.7 miles across Warren and Hinds counties of Mississippi, west of Jackson. EF2 damage, with estimated winds of 120 mph, resulted from a short-lived tornado that covered less than five miles, moving from the Franklin/Adams county line to near Roxie.
[1230 pm] As our teams are hard at work in the field collecting data, have you ever wondered why it takes so long to complete a damage survey?
— NWS Huntsville (@NWSHuntsville) December 17, 2019
We hope to have more information regarding last nights storms around 4pm this afternoon #HUNwx pic.twitter.com/X5t7uVrhLM
In Alabama, the NWS/Huntsville office confirmed EF2 damage in the Colbert Heights area of Colbert County and “at least” EF2 damage in Lawrence County, just west of Huntsville. These reports are likely associated with the same supercell that led to the two deaths at Town Creek. The office also confirmed EF1 damage in the Monrovia area just northwest of Huntsville.
In northeast Mississippi, the NWS/Memphis office found EF2 damage in a nine-mile-long tornado path that passed near Guntown. Two other tornadoes were analyzed in Union and Lee Counties, one rated EF1 and one EF0. Another short-lived EF1 twister passed near Tishomingo, MS.
On Wednesday, the NWS/Tallahassee, FL, office confirmed that an EF2 tornado struck the town of Mystic in southern Georgia at midday Tuesday. The tornado packed top winds of 120 mph and traveled for about 19 miles through Irwin and Ben Hill counties.
Tornado damage in Mystic, Georgia in Irwin County, Georgia. Grace Christain Academy took a big hit.
— Andrew Gorton WTOC (@AndrewGortonWx) December 17, 2019
Photos from Walter Goff. pic.twitter.com/SVWwFnOYfl
How it came together
The potential for at least some severe weather on Monday had been flagged four days earlier by SPC. However, for most of the lead-up period, it looked as if the very potent upper-level dynamics would be at least partially stymied by a lack of sufficiently unstable low-level air. SPC’s outlook early Monday morning called for an enhanced risk of severe weather, the third highest of its five threat levels.
As a powerful upper level storm well captured by models approached the Deep South, sea surface temperatures running well above average across the Gulf of Mexico (1-2°C, or 2-4°F) may have helped to moisten low-level air more than anticipated. By late morning, a belt of unstable air had worked its way into central and northern Louisiana and southern Mississippi, and SPC upgraded its outlook to “moderate” (which is actually the second highest of the five levels). The center noted the “potential for sustained warm-sector supercells” with a risk of “multiple significant tornadoes.”
Most of the day’s storms ended up in a broken line along an advancing cold front. A couple of the most intense supercells stayed just ahead of the front, including the one that spawned the tornadoes affecting Sumrall and Demopolis.
Was reviewing the radar imagery of yesterday's #tornado #outbreak when I suddenly said whoa! upon realizing that the rotation for the tornadoes south of Birmingham in the QLCS originated from that last tornado-producing discrete supercell which merged with the line #mswx #alwx pic.twitter.com/goigrvC70M
— Stu Ostro (@StuOstro) December 18, 2019
One sign of the strong upper-level winds that powered the supercells: the radiosonde launched at 6 am CST Tuesday from the NWS/Birmingham office ended up at Roswell, Georgia, nearly 150 miles away from the launch site. “Farthest balloon recovery from the office that we can recall!” the office tweeted.
Hey @NWSBirmingham look what I found from your 12z launch. pic.twitter.com/Emow5KIu27
— Matthew Smith (@Smitherz08) December 17, 2019
The highest winds in this sounding were 115 knots (about 132 mph) at the 200-mb level, which is typically around 39,000 feet up.
