Search and rescue efforts were underway in the Houston area after a destructive tornado downed power lines, overturned trucks and flooded streets Tuesday afternoon.
The National Weather Service’s Houston/Galveston office has received no reports of deaths or injuries, NWS meteorologist Tim Cady said early Tuesday evening, though the storm continues to march east along the Gulf Coast.
Cady said there are reports of “very widespread structural damage” in Deer Park and Pasadena, southeastern suburbs of Houston.
Deer Park Mayor Jerry Mouton Jr. said during a news conference that about 30 roads in the city were closed and that the Deer Park Independent School District would close Wednesday. He added that several school buildings were damaged.
Mouton said the tornado also hit the San Jacinto Manor assisted-living facility - initially reported as a structure collapse - but none of the 62 patients were injured. He said three patients were hospitalized as a precaution and four were picked up by families, while the remaining patients were split between four facilities.
Cady, the meteorologist, said Pasadena and Deer Park are home to houses and petrochemical plants alike. He said they haven’t received any reports regarding the petrochemical plants.
Cady said he and his staff will evaluate the storm’s strength Wednesday but noted that this is the office’s first time issuing a tornado emergency, which is the service’s most dire alert.
“We’ve done plenty of flash flood emergencies, but this is our first tornado emergency,” he said.
The area went into a tornado watch at 10:50 a.m. local time, Cady said. The first official tornado warning was issued at 2:10 p.m. and the emergency was issued for southeastern Harris County at 2:24 p.m., once they “were very, very confident that there was a large and destructive tornado.”
The threat is over in Houston but not for its Gulf Coast neighbors.
Cady said the storm is set to track through Louisiana through the evening, then across Mississippi and Alabama before arriving at the eastward tip of the Florida panhandle about midnight.
He said the storm is “absolutely still a threat” for those south of Interstate 10.
The NWS office in Lake Charles, La., received a report from a police officer that a twister had crossed Highway 171 just south of a rural area called Ragley, said meteorologist Stacey Denson.
She said her office has received no reports of injury or worse, adding that the storm will have moved through her area near the Texas-Louisiana border about 10 p.m. local time.
“It’s still too early to confirm anything else,” she said.
More than a dozen tornado warnings has been issued as storms tore through the Gulf Coast of Texas, the latest activity in what has already been a blockbuster January for severe weather across the Deep South. An expansive stretch of the Gulf Coast was bracing for severe thunderstorms and possible tornadoes Tuesday.
The National Weather Service Storm Prediction Center has drawn a Level 3 out of 5 “enhanced” risk of severe weather on its outlook maps, signifying the potential for a disruptive and dangerous event. The center is warning of a forthcoming squall line with embedded tornadoes and pockets of straight-line wind damage. The threat along the Interstate 10 corridor could persist deep into the night.
Several large population centers, including Houston; Galveston, Tex.; New Orleans; Gulfport, Miss.; Biloxi, Miss.; and Mobile, Ala., are in the heart of the severe weather risk. Additional severe thunderstorms are probable over the Southeast on Wednesday.
The Storm Prediction Center issued a tornado watch until 6 p.m. Central time for the zone from roughly Corpus Christi, Tex., to Lake Charles, La., cautioning that a couple of “intense tornadoes” are possible. Additional tornado watches may be issued for areas to the east.
The month to date has already featured nearly 140 reports of tornadoes. Some may be duplicates, but regardless, twisters have been swarming the South at breakneck pace. An average January features 36 tornadoes across the Lower 48.
The main severe-weather risk area extends from the Matagorda Peninsula in Texas to southern Alabama and the Florida Panhandle. Western zones will see the threat begin and end earlier, with the storms progressing farther east during the late evening into the overnight.
A Level 3 out of 5 enhanced risk covers the immediate coastline (where instability, or thunderstorm fuel, will be the greatest). That includes New Orleans; Baton Rouge; Mobile, Ala.; Galveston, Tex.; Pasadena, Tex.; and Metairie, La. Much of Interstate 10 weaves through this zone as well, making the hazardous weather a factor that motorists will need to contend with and be prepared for.
A Level 2 out of 5 risk zone borders the enhanced region; it covers Houston and Sugar Land, Tex., as well as parts of the Golden Triangle, including Beaumont, Tex., and Lake Charles, La.
Farther northwest, a Level 1 out of 5 risk splits the difference between greater severe weather odds and general thunderstorms. Corpus Christi, Tex.; Montgomery and Tuscaloosa Ala., including much of the Interstate 59/20 corridor; and Jackson, Miss., are within the marginal zone.
Tornado risk: There will be two “modes” of tornado risk. A quasi-linear convective system (QLCS), or squall line with embedded kinks of rotation, will form during the afternoon or evening hours. That QLCS will probably produce damaging straight-line winds by mixing jet stream momentum to ground level. It could also contain some quick-hitting and fast-moving tornadoes.
Ahead of the mainline, a few isolated rotating or “supercell” thunderstorms may form. Assuming they don’t suffer interference from other storms, any supercells would be able to tap into the atmosphere’s full hostility and produce an isolated significant tornado.
Damaging straight-line winds: Any lines of thunderstorms that develop would probably produce winds in the 50 to 65 mph range.
Hail: Because thunderstorms won’t be particularly tall (not reaching high into the atmosphere where it’s coldest), hail probably won’t be a primary concern. That said, a few instances of quarter- to half-dollar-sized hail can be expected.
Heavy rainfall: An inch or two of rainfall is expected with storms along the Gulf Coast, though East Texas and western Louisiana could see 2 to 3 inches where downpours “train,” or move repeatedly over the same areas. That would run the risk of localized urban and poor drainage flooding.
This is an unusually low-confidence forecast. Meteorologists largely struggle forecasting the impacts of HSLC, or “High Shear/Low CAPE” setups - in other words, environments characterized by an abundance of spin, but minimal instability or energy supplied by humidity and warmth to fuel thunderstorms.
We know that any cloud that grows high enough into the atmosphere will probably rotate. That’s because of the abundance of shear, or a change of wind speed and/or direction with height. But how tall will thunderclouds blossom? That hinges on the availability of instability, which is in question.
The greatest propensity for severe weather will be along the immediate Gulf of Mexico coastline, where ocean-heated moisture-rich air will waft northward. Risk will drop off appreciably once one heads more than a few counties inland.
The meteorological setup
At present, a low-pressure system is swirling through west Texas near the Big Bend, heading for the Permian Basin; it’s spreading snow from northern Texas into Oklahoma and northwest Arkansas.
Southerly winds on the eastern side of the low pressure zone are drawing moisture and warmth northward, much of which is riding up and over a lip of cold, dense air hugging the ground:
That’s already creating “elevated” thunderstorms, or storms rooted in warm air at the mid-levels, atop the wedge of cold. Those thunderstorms were spreading over much of Central Texas late Tuesday morning but won’t pose a tornado risk. Some may produce gusty winds and hail though.
The warm front setting of these storms was lifting north, and it’s likely that “surface-based” thunderstorms will blossom by early Tuesday afternoon in the “warm sector” as air in the 60s and 70s comes ashore and claims more territory.
Weather models depict thunderstorms blossoming in that warm, moist region near the coast around midday. They’ll move into the Houston-Galveston area shortly thereafter, with a robust tornado threat by midafternoon.
Storms will then shift toward the Louisiana border and Golden Triangle during the evening, reaching New Orleans after dark approaching midnight.
Parts of Mississippi, coastal Alabama and the Florida Panhandle will see an overnight severe weather threat.