An abundance of atmospheric moisture resulted in historic rainfall totals across the Dallas/Fort Worth area from 21-22 Aug 2022, leading to flash flooding and power outages in the area. NWS 1-day QPE for the two days show widespread areas of 3+” each day, with localized pockets of 6+” (Figure 0.5). COCORAHS shows widespread 2-day totals in excess of 6″, with several obs over 10″.
The CIRA Advected Layer PW product captured the evolution of mositure through the four layers in the days leading up to the event. The two lowest layers captured the southerly surge of Gulf moisture into the area, while the two upper layers revealed southwest US monsoon moisture drift east across the area. The development of abundant deep moisture over the region, captured in the ALPW product, meant the atmosphere would support locally heavy rainfall.
Forcing mechanisms for convective development included a northeastward surging outflow boundary into the region on the 21st, and a nearly stationary west-east frontal boundary draped across the region. Upper level support came in the form of a ~700 mb low moving across the region during the evening of the 21st into the 22nd, along with the right entrance region of an upper level jet.
GOES-16 7.34 um (LLWV) imagery combined with 700 mb height and 250 mb wind speed RAP analyses and GOES DMWs helps to highlight these features and connect the model analyses to the satellite observations. The ~70 knots 250 mb jet is clearly apparent in the RAP analysis extending west to east from New Mexico to Tennessee. The Satellite imagery supports the analysis with the presence of fast moving clouds through the jet core. GOES-16 DMWs quantify the movement of clouds and water vapor in the imagery, and capture the jet entrance region over OK/N TX, with UL winds (reds) quickly increasing from 20 knots to 50 knots west-east. The broad 700 mb low is easily diagnosed in the model analyses moving east from New Mexico to east Texas, but is a little harder to identify in the imagery. One can analyze a broad couplet of warming (dark gray)/cooling (light gray) from west to east in the imagery centered over and shifting east with the RAP 700 mb low. The mid-level DMWs (blues) effectively capture the cyclonic flow around the low as it advances east across west and north Texas.
GOES-East VIS/IR sandwich (day) and IR (night) imagery shows the full evolution of heavy-rain-producing thunderstorms over the Dallas/Fort Worth area from the 21st to the 22nd. GOES TPW overlay (large purple blocks) measure values between 2.0 and 2.5″ prior to cloud cover taking over. The northeastward surging outflow boundary is apparent early in the period kicking off scattered storms. Widespread thunderstorms develop thereafter, aided by the frontal boundary and mid-level low. Storms consistently produce overshooting, and very cold, tops over the areas associated with heavy rainfall. Eventually, the thunderstorm complex shifts east and south with the evolution of the forcing.
Overnight on the 21st, NOAA-20 VIIRS provided a detailed look at the thunderstorms in the 375m I5 IR band. Numerous OTs are apparent in this image, including very small scale, with cloud top temperatures as cold as -86C sampled.
Examples of 1-min imagery from this event, including an example of a RGB/L2 product readout combo, can be found in this CIMSS Satellite Blog Post.
Bill Line, NESDIS/STAR