Severe weather developed across the central Plains to upper Midwest on Memorial Day 2022 (May 30). Storms were forced by a potent shortwave trough rounding the base of a broad central US upper trough, and associated surface boundaries.
Per SPC 13Z Day 1 Outlook: “A large field of mid/upper-level cyclonic flow covers most of the
western/central CONUS, anchored by a broad, complex cyclone covering much of the northern/central Rockies and Intermountain region. Primary vorticity maxima are evident in moisture-channel imagery over ID and central/eastern CO. The latter will eject northeastward today, become a compact, closed cyclone in its own right, and deepen considerably, with the 500-mb low reaching east-central SD by 00Z.”
The aforementioned shortwave originating in Southern Colorado around 10Z is analyzed in the following water vapor animation as a west-to-east couplet of warm (drying, descending) and cold (moistening, ascending, cloud development) lifting northeast into the central plains along the southeast periphery of broad cyclonic flow. The drying on the backside and leading moistening/convective activity become more pronounced later in the day as the wave strengthens and lifts into the upper midwest. Overlaying model analysis fields can bolster ones understanding of the water vapor imagery observations, with height fields capturing the broad upper trough and, sometimes, smaller-scale shortwaves, wind field revealing upper level wind jet structure, and surface fields showing the patterns influence on the surface pressure pattern.
Locally, NWS Omaha, NW discusses: “Recent surface analysis and satellite observations place a deepening surface low north of Yankton, South Dakota, with a southward extending dryline that is draped along the Nebraska/Iowa border and strong gradient winds have been observed on both sides of the feature (with gusts up to 46 kts). Water vapor imagery highlights the deepening mid-level support with a strong punch of dry air moving northward behind the aforementioned surface low.”
NWS, Des Moines, Iowa provided a great analysis of satellite imagery in a mid-day AFD: “Lots of goodies one can pick up on satellite ahead of the strong to severe weather potential later today/tonight. As of early this afternoon you can clearly pick up on the potent shortwave rounding the base of the negatively tilted trough that is responsible for aiding a deepening surface low, a strong dry slot/dry air intrusion moving northward through portions of C/E Nebraska and E South Dakota, and the explosive convection along its leading edge. Additionally on visible satellite imagery, a sharp surface dry line is seen sliding into E Nebraska and drops back into C Kansas. Ahead of the surface dry line, satellite imagery corroborates hi-res guidance depictions of an area of potent low- mid level moisture transport with mid-level cellular cloud cover. Many of the aforementioned goodies will affect portions of Iowa tonight as the parent trough continues to translate northeastward, leading to the potential for strong to severe storms as well as a potential sting jet.”
Associated visible imagery is shown in Figure 2, along with Day Cloud Phase Distinction RGB Imagery in Figure 3. The DCPD RGB imagery provides a little more context to the VIS, including areas where cu are beginning to glaciate/initiate. Slightly earlier, SPC also discussed development along the northern part of the dryline here.
Northward moisture transport ahead of the dryline is also diagnosed in GOES-16 TPW imagery as a narrow corridor of 1.25″+ TPW.
Convection continued to develop south along the dryline, as analyzed in satellite imagery and discussed in a later SPC MCD here. This evolution was captured in a 1-min sector.
Later around and following sunset, the cold front caught up with the retreating dryline, leading to another round of convective initiation. While surface obs provide some information about the evolution of these boundaries, satellite imagery captures their movement in much more detail, temporally and spatially. In this case, the GOES-16 Split Window Difference appears to have captured both boundaries quite well leading up to and through their interaction.
One could also follow the evolution of the boundary interaction in Nighttime Microphysics RGB imagery (which forecasters would want to be viewing anyway post transition to night), which includes the SWD along with the IRW and Night Fog Diff. In this RGB, convective evolution is analyzed by transition from Blue to Pale Cyan (development of liquid cloud), and then to Red (glaciation/cooling). Using satellite imagery to track boundaries in this manner helps forecasters better anticipate where and when convection will develop, important for mesoanalysis, and which could be communicated in forecast discussions, social media, and other DSS means.
Bill Line, NESDIS/STAR