A Mesoscale Convective System (MCS) containing a line of severe thunderstorms rolled across south Texas early in the morning on 03 May 2019. GOES-16 1-min imagery was available over the region to support forecast and warning efforts. One-minute IR imagery indicated a broad region of overshooting tops with gravity waves emanating out away from the updrafts (Fig 1). Gravity waves across the top of a convective system are formed when the updraft interacts with the stable tropopause. A strong updraft may “overshoot” the tropopause into the lower stratosphere, appearing as an overshooting top. In an effort to return to equilibrium, these air parcels go on to oscillate (sink and rise) past that equilibrium level. This air reaching and overshooting the tropopause is forced to oscillate outward and downstream by the mean flow, appearing as “waves” at the storm top.
Transverse banding (buzzsaw looking cloud area) was apparent in the imagery north of the main updraft region. These mid-upper level clouds are an indication of potential aircraft turbulence. There were indeed several aircraft reports of moderate turbulence through these cloud features.
GLM flash extent density overlaid on gray-scale IR imagery from the same period highlights the storm cores (highest lightning rates), as well as lightning flashes extending well away from the updrafts through the anvil region (Fig 2). The average flash area confirms smaller flashes associated with the active/newer updrafts, with longer flashes in the anvil away from the main updrafts.
One-minute visible imagery at sunrise revealed the storm top features in much greater detail, including the very active updraft/overshooting top region, and series of gravity waves across the anvil.
Bill Line, NWS