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″.

Figure 0.5: Slideshow. Image 1 and Image 2 are AHPS 1-day QPE ending at 12z on the 22nd and 12z on the 23rd, respectively. Image 3 is COCORAHS 2-day rainfall totals, ending the morning of the 23rd.

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

No, VIIRS did not capture a Donut dropping powdered sugar near the North Pole! On 12-13 Aug 2022, the VIIRS Snowmelt RGB revealed a Polar Mesoscale Cyclone depositing fresh snow across the Arctic, which was apparent under the clear skies in its wake (Fig 1 and 2). The unique combination of spectral channels, not available on GOES-R series ABI, allows for one to differentiate fresher snow cover from older snow cover and ice (see other examples here and here). In this case, the most recent snow cover is obvious as a trail of a relatively lighter shade of blue atop the darker shades of the older snow cover. In fact, one may note three distinct shades of blue, or snow ages, in this domain. The background/oldest snowpack on ice appears as the darkest shade of blue, the most recent swath the lightest, and a series of swaths perpendicular to the recent swath that exhibit shades of blue somewhere in the middle (Fig 3).

The Snowmelt RGB can be useful operationally, including at lower latitudes, for determining the type of precipitation that has fallen (rain, snow, freezing rain), assessing the blowability or runoff/flooding potential of snow cover, and as a tool to determining cloud microphysics. The VIIRS Snowmelt RGB can be viewed online at the CIRA SLIDER, and very soon, to a CIRA SLIDER – VIIRS CONUS sector to better accommodate the viewing of VIIRS imagery over CONUS.

Bill Line (NESDIS/STAR), Curtis Seaman (CIRA), John Forsythe (CIRA), Carl Dierking (UA/GINA)

GOES-West Operational Interleave began today (8/1) at 1700 UTC, and will continue through Sep 6. What does this mean to NWS users? GOES-West ABI Imagery (single-band imagery, band differences, RGBs) is now from GOES-18. Other GOES-West products, such as from GLM, and ABI derived products (cloud products, TPW, DMWs, etc) remain from GOES-17. Hence, “Interleave”. Why? GOES-18 ABI Imagery reached Provisional Validation maturity on July 28, meaning it is suitable for the broad user community. We are also entering a GOES-17 ABI Warm Period, which results in degraded GOES-17 LWIR imagery due to the cooling system failure. Therefore, the GOES-18 imagery will be distributed instead of that from GOES-17 from 8/1 to 9/6. The transition on 8/1 was successful, with GOES-18 imagery appearing in NWS AWIPS, as well as webpages like CIRA SLIDER and the STAR GOES Image Viewer.

From an AWIPS SBN perspective, no changes were needed at the individual locations. GOES-West imagery (from GOES-18) is loaded from the menu system as one normally would. Procedures containing GOES-West imagery load as usual. If you load imagery from the product browser, you will notice the addition of GOES-18 to the “Satellite” drop-down. The GOES-18 label will now appear in the product legend. GOES-West meso sector requests will continue as usual, with the meso sector imagery coming from GOES-18.

One may notice vertical striping at night in the Nighttime Microphsyics RGB and Nighttime Fog Difference. Details of the subtle GOES-18 Ch07 “Barcode Artifact” can be found here.

The transition from GOES-17 to GOES-18 imagery at 1700 UTC is shown below in various Imagery products. All examples begin with GOES-17, and transition to GOES-18 after 1700 UTC (midway through each animation). All examples are saved from AWIPS (SBN dataflow), with the exception of Geocolor, which was captured from CIRA SLIDER. Since we are already entering the warm period, the imagery degradation can be seen in the impacted GOES-17 imagery.

Starting with Ch08 Water Vapor imagery, the transition from GOES-17 to GOES-18 at 1700 UTC is obvious, as the horizontal striping associated with the cooling system failure is apparent in the GOES-17 portion of the animation, but abruptly disappears in the GOES-18 portion. The GOES-18 imagery appears as one would expect, similar to that from GOES-16.

GOES-17 Ch13 is not as impacted by the cooling system failure, and therefore, the transition to GOES-18 is very smooth with no noticeable changes in imagery.

Split Window Difference imagery, which is used for the detection of blowing dust and moisture gradients, appears significantly cleaner in the GOES-18 imagery. Channel differences typically enhance noise present in imagery.

The Airmass RGB, which includes multiple LWIR channel differences, is also notably improved with the transition to GOES-18.

The Nighttime Microphsyics RGB, which also employs multiple IR channel differences, exhibits significant noise in the GOES-17 portion, and very little in the GOES-18 portion. Note, this animation is during the daytime, so influence of the ch07 “Barcode Artifact” is not apparent here in GOES-18 imagery.

GOES-17 to GOES-18 1-min mesoscale sector imagery is shown in the next animation. The transition to GOES-18 after 1700 UTC is not discernible.

The transition is also seamless in Geocolor imagery, shown in the final figure from GOES-17 and GOES-18 full disk imagery.

Bill Line, NESDIS/STAR and CIRA