Large hail caused multiple injuries at the Red Rocks Amphitheater to the west of Denver on 21 June 2023 (News story 1, 2, 3; see also this tweet from the NWS in Boulder at 0326 UTC). This occurred in a region that the Storm Prediction Center flagged as in an atmosphere with an Enhanced Risk of severe weather. The principal severe threat was hail. The animation above shows the RealEarth display of ProbSevere (version 3) and it shows the approach of the radar object that produced the hail; a severe thunderstorm warning was in place. The image below shows the probSevere readout at 0330 UTC; the yellow ‘X’ approximates the location of Red Rocks.

ProbSevere allows a readout of the components used in the probability computations. The Radar Object nearing Red Rocks in the image above is #344797 — and time series of the parameters are shown below (available in interactive form here for a few days). Hail has much larger probabilities than either wind or tornado in this case. Maximum Expected Hail Size at 0330 UTC was 2.46″.

Shortly after 0330 UTC, the radar object associated with the large hail over Red Rocks merged with the radar object to its east, radar object #345162, and its time series is shown below. Note the peak in ProbHail probabilities around 0330 UTC.

---

ProbSevere LightningCast Probabilities also showed an enhanced threat of lightning for the hours surrounding the hail event, as shown below. The LightningCast contours shown below are not parallax-corrected (the ABI data are not parallax-corrected either). Thus the features are displayed farther from the sub-satellite point (at 0^oN, 75.2^oW) than in reality (as discussed here).

---

This tweet describes the ground-based lightning observations near Red Rocks in the hours surrounding the hail event.

View only this post Read Less

As also discussed in this blog post, large hail injured as many as 90 people at a Red Rocks outdoor concert in Colorado just after local sunset on 21 June 2023. 1-minute Mesoscale Domain Sector “Clean” Infrared Window (10.3 µm) images (with/without an overlay of GLM Flash Extent Density) from GOES-16 (GOES-East) (above) and GOES-18 (GOES-West) (below) showed the east-northeastward motion of the parent thunderstorm, and the resultant path of damaging wind and large hail reports. Red Rocks Park is located near the center of the GOES-16/GOES-18 images.

Pulses of overshooting tops exhibited infrared brightness temperatures as cold as -72ºC at 0317 UTC (below) — which was about 9 minutes prior to the Local Storm Report of 2-inch diameter hail at Red Rocks — and that cold overshooting top occurred during a brief lightning jump (from 0311-0318 UTC), as indicated by GLM Flash Extent Density. Note the differences in parallax offset between the 2 satellites — a 50,000-ft cloud top feature over central Colorado would be displaced about 22 km (13.7 miles) to the northwest of its actual surface location in GOES-16 imagery, but displaced about 23 km (14.3 miles) to the northeast of is actual surface location in GOES-18 imagery. Parallax correction would therefore have displayed the cold overshooting top closer to the location of the 1.75-inch diameter hail report.

The CIMSS-produced full resolution (nominal 2 km) CLAVR-x Cloud Top Height of the coldest overshooting top was around 56,000 ft (below).

View only this post Read Less

Orbits from NOAA-20 (link, from this site) show a NOAA-20 overpass over Tropical Storm Bret at around 1700 UTC on 21 June 2023. Data from NOAA-20 were available at this site by 1730 UTC, and downloading files from the VIIRS-I1-SDR and VIIRS-IMG-GEO directories (as discussed in this blog post), and running a simple Polar2Grid (software downloadable here) command yields the full-resolution image above. For ascending (daytime!) passes, then, this could be done within 45 minutes. This particular image was posted on the blog by about 1840 UTC.

---

Of course, you might not want all the imagery outside the Tropical Cyclone! Polar2Grid allows for simple definitions of grids (via the p2g_grid_helper shell script: ./p2g_grid_helper.sh GridName -52.0 13.0 375 -375 1440 1440 > $POLAR2GRID_HOME/FileName.yaml). An I01 visible image (0.64 µm) centered near Bret with the defined grid in the command above is shown below.

View only this post Read Less

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Clean” Infrared Window (10.3 µm) images (above) showed Atlantic Tropical Depression Three as it intensified to become Tropical Storm Bret at 2100 UTC on 19 June 2023. Overshooting tops exhibited infrared brightness temperature values as cold as -79ºC.

Bret was in a favorable environment for continued intensification, as shown by low values of deep-layer wind shear from the CIMSS Tropical Cyclones site (below) — and the storm was moving over relatively warm water (Sea Surface Temperature).

View only this post Read Less