Widespread strong to severe thunderstorms developed across Argentina during the day on 18 December 2020. To capture the phenomena, a GOES-East meso-sector (-1) was positioned over the region, per a international request via the NESDIS Satellite Analysis Branch, which read, “Possible explosive cyclogenesis over central Argentina may bring heavy rains with possible severe thunderstorm and high surface winds”. GOES-East Full Disk water vapor imagery captured the evolution of a compact shortwave trough moving onshore in western South America and helping to spark widespread thunderstorm development (Fig 1).
A long duration (5-min-updating) IR-Window animation of the full mesoscale sector captures the evolution of the thunderstorms from the early day into the early nighttime (Fig 2). Not only are widespread thunderstorms detected, but an outflow boundary/cold front is analyzed racing north in the wake of the thunderstorms, adjacent to the high terrain, over the northwest portion of the sector (diagnosed as a sharp transition to relatively light gray, or cool, brightness temperatures).
First focusing on convective initiation for some of the most impressive, in appearance, thunderstorms, the Day Cloud Phase Distinction RGB, (at 1-min resolution) captured the trend from growing cu field (cyan clouds), to glaciation (cyan => green), to failed updraft attempts and orphan anvils (red/yellow) (Fig 2).
Playing the full animation, successful convective initiation is observed shortly thereafter (Fig 3). Note, the RGB shown was modified from the default recipe, which quickly reaches the max threshold for the reflectance components during the summer. In this example, the green (0.64 um) component max was raised to 105%, while the blue (1.61 um) component max was raised to 65%. After making the adjustment, cloud top texture becomes apparent.
Following initiation, thunderstorms quickly matured and developed impressive storm top signatures, including rapidly expanding anvil, abundant texture, overshooting tops, and long-lived above anvil cirrus plumes, per 1-min VIS (Fig 4). In this example, a color table focusing on higher reflectance was utilized in order to best capture the storm top detail.
Over the same region and time period, a 1-min VIS-IR sandwich overlay provides more insight about the storm top features by adding brightness temperature information (Fig 5).
Now turning attention to activity near the outflow/cold front progression and lofted dust was apparent along and behind the boundary per 0.64 um VIS (Fig 6) and daytime Geocolor imagery (Fig 7). The DEBRA Dust product highlighted regions of most likely dust (Fig 8). The blowing dust along and behind the boundary apparent in the imagery acts as a fluid tracer of the dense air as it flows within the valley and interacts with higher terrain. Video of the blowing dust was captured from the region (see here and here).
A Dust-Fire RGB not only shows the blowing dust (bright green), but also indicates wildfire hot spots (isolated pixels of bright red) in the scene (Fig 9). A large hot spot is detected in the southeast portion of the scene early in the period, while two smaller hot spots are found in the left center portion of the scene ahead of the cold front and blowing dust. Deep convection appears as blue, drier boundary layer as medium green, and a relatively moist boundary layer as medium-dark red.
Finally, a longer VIS-IR transition animation captures the full evolution of the boundary and related blowing dust into the evening (Fig 10).
Bill Line, NESDIS and CIRA