A significant severe weather event impacted E TX, LA, and MS on Sunday, April 2. A SPC Moderate Risk for severe had a region upgraded to High at the 1630 UTC Day 1 outlook for the tornado threat. Given the threat, GOES-East RSO was requested by SRH, and Mesoscale Domain Sector 1 granted over the region. The early day setup included a closed upper low moving NE across central Texas towards Arkansas. At the surface, an MCS and associated cold pool from the previous evening was traversing eastward through Texas. Ahead of this feature, strong southerly flow drew up warm, moist Gulf air.
The evolution of the overnight MCS is depicted in 5-min GOES-16 ABI 10.4 um clean window IR imagery below. This channel is the “cleanest” of the IR channels because it is least sensitive to absorption by atmospheric constituents such as water vapor. The development of thunderstorms during the evening of the 1st is seen as rapid cooling of the cloud tops in SW Texas. The rapid expansion of the cold cloud tops signals the continued maintenance of convection, and development of an MCS. By early morning on the 2nd, rapid warming becomes evident, especially on the southern end of the MCS, signaling a weakening and dissipation of thunderstorm activity. The higher spatial (2km vs 4 km) and temporal (5-min vs 15-min over CONUS) resolution of the GOES-16 satellite allows for these cloud top temperature trends to be more easily and promptly diagnosed.
By late morning, convection began to develop within the warm sector in E Texas and Louisiana ahead of the previous evening’s weakening cluster of thunderstorms. These storms quickly became severe, producing large hail, wind and tornadoes. Detection of convective initiation is significantly improved in the 1-min, 0.5 km visible imagery, as was shown in a previous blog post that compared GOES-16 data with GOES-13 data for initial storm development.
Storm top features of mature convection are also easier to discern in the GOES-16 imagery compared to current GOES satellites. Below is a side-by-side comparison of 0.5 km, 1-min VIS from GOES-16 and 1 km, Rapid Scan (5-15 min) VIS from GOES-13. Additionally, GOES-16 2 km, 1-min IR is compared with GOES-13 4 km, Rapid Scan IR. The time period is 2145 UTC to 2315 UTC. Storm top features apparent that are associated with strong-severe weather at the surface include overshooting tops, enhanced-V’s, and above-anvil cirrus plumes. Gravity waves emanating from the updrafts, indicators of turbulence and caused by strong updrafts, are also more obvious in the GOES-16 data.
The Geostationary Lightning Mapper (GLM) is the other new earth-pointing instrument aboard the GOES-R series of satellites, and can detect total lightning activity with uniform detection efficiency. Data from the GLM are not yet available, however ground-based networks can be used to get a feel for how GLM data will generally look in AWIPS. Plotted is GOES-16 2-min visible imagery with Earth Networks 1-min Total Lightning Pulse density data, binned in 8-km grid boxes to match the resolution of the GLM, overlaid as semi-transparent. Pulses are a very basic variable, and when binned into grid boxes over a time period, provide a good measure of fluctuations in lightning activity. Max’s in total lightning density activity signify the core updraft regions of thunderstorms, which are also represented in visible imagery by a high degree of texture and overshooting tops. Rapid increases in lightning density signify rapid upticks in updraft strength, and thunderstorm intensification. Similarly, decreasing trends in total lightning activity will signify a weakening storm.
By early evening, the strong/severe storms had organized into a linear system, and while the severe threat had lessened, a flash flood threat had begun. A separate post will be written with details about the flood event.
– Bill Line, NWS
“The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. Users bear all responsibility for inspecting the data prior to use and for the manner in which the data are utilized.”