A remarkable shortwave trough brought widespread strong to severe thunderstorms to the Mississippi River Valley region during the day/evening of 28 March 2020.
GOES-East 6.2 um water vapor imagery with RAP field overlays provides an excellent view of the synoptic setup and evolution during this event (Fig 1). Features such as the positions of the low and upper level jet core as depicted in model analyses (such as the RAP here) are confirmed/corrected through analysis of the water vapor imagery.
Focusing in on the Midwest, convection developed along a dryline and warm front, with thunderstorms eventually producing large hail and tornadoes. The GOES-East Split Window Difference (SWD) and Infrared Window Combo imagery (available on the STOR) captures the evolution of the dry air north and east around the southeast portion of the deepening cyclone, and convective initiation along it’s leading edge (Fig 2). The GOES imagery provides better horizontal spatial and temporal resolution when compared to surface observations and surface analyses (hourly RAP surface equivalent potential temperature shown here). The simple gray scale color table of the SWD shows relatively dry low-level air as darker gray, with relatively moist regions lighter gray. An overlay of IR window is provided for cold brightness temperatures (clouds) as non-gray colors). The dry air is diagnosed surging northeast through eastern Kansas into northern Missouri and southern Iowa. Convection develops along the dryline, as diagnosed in the SWD imagery, across Iowa.
While the GOES-East TPW derived product also captured the punch of drier air northward and dryline boundary evolution (at lower spatial res), the CAPE product only ever shows values less than 500 j/kg (Figs 3 and 4). This is lower than what was observed by radiosondes and what was computed by model analyses and the SPC mesoanalysis.
One-minute imagery from GOES-East was available across the region during this event. Day Cloud Phase Distinction 1-min imagery showed deepening cumulus clouds along the dryline, with a transition from cyan to green indicating glaciation and imminent convective initiation (Fig 5). Continued vertical growth and transition to yellow and red colors indicates further glaciation and cooling of cloud tops, and that convective initiation has occurred. Shortly thereafter, the first lightning flashes occurred with these storms per GLM FED data. FED values then increase quickly leading up to the first reported tornado. All of this is apparent in real-time given the very low latency (<1-min) of the 1-min imagery.
Polar passes from SNPP (x2) and NOAA-20 meant three VIIRS images within about a 1.5 hour timeframe. This imagery provided higher spatial detail in the cloud field as convection began to initiate along the dryline. Day Cloud Phase Distinction RGB imagery created from the VIIRS 375 m I bands allows for the diagnosis of highly detailed glaciation trends in the cloud field (Fig 6).
Further south, strong thunderstorms developed within the broader cloud shield over northeast Arkansas, with one storm producing a tornado that caused damage and injuries across Jonesboro, AR. GOES-East 1-min visible imagery with GLM semi-transparent overlay shows increasing visible texture through the broad cirrus shield as the storm approaches Jonesboro from the southwest (Fig 7). FED values increase quickly as well just prior to/during the development of a tornado, with MRMS low-level rotation tracks confirming significant rotation as the storm advanced through the town.
Bill Line, NESDIS and CIRA