A broad trough and embedded shortwaves digging east across the southern US brought severe weather, including tornadoes, to parts of the south and southeast US on 21-22 March 2022. The evolution of the trough across the country is shown well in 6.2 um GOES-East Water Vapor Imagery in Figure 1. GLM FED is also included in the animation as progressively more opaque yellow atop the green cold clouds.
Adding RAP sfc and upper level analysis fields onto the water help one to better understand features in the imagery by associating them with familiar fields, such as 500 mb height and wind speed, and sfc pressure (Figure 2).
Partially overlapped GOES-East 1-min mesoscale sectors resulted in a corridor of 30-second imagery across central Texas. The difference between 30-second imagery and 1-min imagery may not sound like a lot, put processes that are occurring on such small timescales do appear notably smoother to the human eye in the side-by-side comparison. This is exemplified in an animation of visible imagery over a tornado-producing severe thunderstorm on the border of 30-sec and 1-min imagery (Fig 3).
Further south near San Antonio, the evolution of the cu field leading up to eventual convective initiation is captured in 30-second Day Cloud Phase Distinction imagery. The 2.5 hour animation (300 images) reveals a cumulus field becoming increasingly agitated with the growth of cumulus clouds into towering cu, eventual glaciation with the colors changing from blue/cyan to green, to convective initiation diagnosed by vertical growth and transition of colors from green to yellow/red (Fig 4). The growth of the eventual first severe-warned storm occurs under high cirrus (red), but can be followed in the very high temporal resolution imagery.
Post convective initiation, 30-second imagery of storm maturation captured the evolution of storm top features, such as overshooting tops and an above anvil cirrus plume, in much detail (Fig 5). The imagery is extremely fluid, and ensures forecasters are receiving updates about the storm faster than ever. The animation is 240 images, or 2 hours long.
During the same period of 30-second imagery, adding a semitransparent 10.3 um overlay, resulting in the VIS/IR Sandwich, helps to capture the storm top features a little better by including the quantitative brightness temperature information (Fig 6).
After viewing the 30-sec animation a few times, take a peak at the 1-min animation of the same scene. It is fascinating how 1-min imagery appears relatively “choppy” (Fig 7)!
The most impressive storm developing near San Antonio exhibited an exposed updraft in the GOES-East 30-second imagery. Rocking a 30-sec visible imagery animation of this storm over a 25 minute period reveals counterclockwise rotation of the updraft (Fig 8). Extending west of the updraft is the more horizontally oriented flanking line. Inflow feeder clouds are also analyzed southeast of the updraft, as well as an overshooting top and above anvil cirrus plume at the storm top. Given the presence of high clouds, and rapid evolution, some of these features can easily be missed in coarser temporal resolution imagery.
As was shown in Figure 1+2, the convective threat shifted east to the southeast on the 22nd as the broad upper trough shifted east and another shortwave and associated strong jet streak spread across the region. Two strong thunderstorms passed through the New Orleans area just after sundown, and were captured in GOES-East 1-min ABI and GLM imagery. The northern storm produced an EF1 tornado, while the thunderstorm produced an EF3 tornado. The 1-min IR imagery revealed rapidly cooling cloud tops just prior to the initial tornado reports between 0024 UTC and 0029 UTC (Fig 9).
GLM FED associated with the storms included rapid upticks in total lightning activity leading up to tornado development (Fig 10). The FED data highlights the location and movement of the most intense storm updrafts, as well as the presence of lightning flashes and resulting lightning danger well removed of the storm core.
Finally, combining the GLM Flash Extent Density with Minimum Flash Area into a single RGB reveals where an abundance of small flashes (indicative of strengthening updraft) were occurring, as bright shades of yellow (Fig 11). Red represents low FED and small flashes, so a transition from Red to Orange to yellow in this RGB indicates increasing numbers of small flashes. Shades of blue represent long flashes, which are often present with the anvil regions of the thunderstorms, as well as with decaying updrafts.
Bill Line, NESDIS and CIRA