March 21, 2022, marked the beginning of a severe weather and tornado outbreak that affected Texas and the Southeast United States. This 3-day event produced 78 tornadoes in total, including 12 EF-2 and 3 EF-3 tornadoes. Figure 1 shows the low-pressure system associated with this outbreak, centered over southeastern New Mexico with a center of 1000 mb. The dryline extending southward from the center through west Texas divides two air masses: a warm, dry air mass to the west of the feature likely originating from the surrounding desert, and a warm, moist air mass to the east of the dryline originating from the Gulf of Mexico. This feature contributed to the unstable atmospheric environment responsible for producing deadly tornadoes.
Figure 1: Surface Analysis Plot valid 1200 UTC 21 March 2022. Brown contours represent mean sea-level pressure in mb. Red “L” represents low pressure centers; Blue “H” represents high pressure centers. Red lines with semi-circles are warm fronts; blue lines with triangles are cold fronts. Orange line with semi-circles represents a dryline feature.
Credit: NWS Weather Prediction Center
Cyclonic relative vorticity can provide information on the vertical structure of surface cyclones, and how they are expected to change over time. Figure 2 shows the surface cyclone centered over eastern New Mexico, and the respective upper-level vorticity maximum positioned to the west of the low center. This implies a westward tilt with height, so we should expect to see an upper-level trough base to the west of the surface cyclone center. This leads to upper-level divergence and subsequent upward vertical motions to the east of the surface cyclone. Air should converge at the surface, lowering the mean sea level pressure and strengthening the surface cyclone.
Figure 2: 500 mb Vorticity plot valid at 1200 UTC 21 March 2022. Solid black contours represent geopotential height in dam. Red dashed contours represent temperature in Celsius. Blue contours represent ascent/upward vertical motion in units 5*10^-3 hPa/s. Cyclonic relative vorticity represented by color bar on the bottom of figure in units *10^-5 1/s; darker colors represent larger values of cyclonic relative vorticity; lighter colors represent lower values of cyclonic relative vorticity. Wind barbs are wind in knots. “L” represents surface low relative to 500 mb; “X” represents vorticity maximum.
Credit: Alicia Bentley Maps
As expected, over the next 48 hours, the surface cyclone strengthened as it propagated northeastward. Figure 3 shows the cyclone over southeast Iowa with a center of 996 mb and a cold front extending southward from the center into the southeast United States.
Figure 3: Surface Analysis Plot valid 1200 UTC 23 March 2022. Brown contours represent mean sea-level pressure in mb. Red “L” represents low pressure centers; Blue “H” represents high pressure centers. Red lines with semi-circles are warm fronts; blue lines with triangles are cold fronts.
Credit: NWS Weather Prediction Center
We can use mid-level water vapor imagery to identify the type of cold front, and what conditions to expect from it. Figure 4 shows the brightness temperatures of water vapor in the mid-troposphere. There is a clear gradient between temperature values over Georgia, with warmer values to the east of the gradient, and colder values to the west. This is known as a deformation zone. By looking at Figure 3, we see that the cold front of interest extends southward into Mississippi, and the deformation zone is located in front or ahead of the cold front. This implies a katafront, and we should expect to see precipitation ahead or along the cold front.
Figure 4: Mid-Level Water Vapor Imagery valid at 1200 UTC 23 March 2022. Warmer colors represent higher brightness temperatures in Celsius; Cooler colors represent lower brightness temperature values in Celsius
Credit: RAMMB at Colorado State University
Figure 5a shows radar reflectivity as two EF-0 tornadoes touched down in Snook, Texas around 8:00 pm CDT on March 21st. Moments before the tornadoes touched down, the band of reflectivity over Snook can be seen “bowing” inward. This is known as a bow echo which can produce straight-line winds and tornadoes. We can estimate the general direction of the tornadoes using Figure 5b, which shows storm relative velocity. With the radar site being located in College Station, we can see that the green signature, which indicates motion towards the radar site, is located southwest of the radar site. The red signature, which represents motion away from the radar site, is located north of the radar site. Given these signatures, it seemed like both tornadoes were headed northeast towards College Station, but luckily, dissipated after being on the ground for about 1 mile and 0.3 miles respectively.
Fig 5a Fig 5b
Figure 5a: Radar Reflectivity valid at 0100 UTC 21 March 2022. Color bar represents intensity in units dBZ. Warmer colors represent more intense precipitation; Cooler colors represent less intense precipitation.
Figure 5b: Storm Relative Velocity valid at 0100 UTC 21 March 2022. Green indicates motion towards the radar site; Red indicates motion away from radar site. Color bar represents velocity of wind in knots. Warmer colors represent positive values; Cooler colors represent negative values.
Credit: National Weather Service