Large hail in Texas

April 28th, 2021 |

GOES-16 “Red” Visible (0.64 µm) images and “Clean” Infrared Window (10.35 µm) images, with plots of SPC Storm Reports [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) images (top) and “Clean” Infrared Window (10.35 µm) images (bottom), with plots of SPC Storm Reports [click to play animation | MP4]

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images and “Clean” Infrared Window (10.35 µm) images (above) include time-matched plots of SPC Storm Reports of large hail produced by supercell thunderstorms that developed and moved eastward across southern Texas on 28 April 2021. Hail as large as 4.00 inches in diameter was listed in the SPC Storm Reports, but one giant hailstone was found whose diameter was 6.4 inches (Update: this hail was confirmed to be a Texas state record):



Vigorous overshooting tops were seen in both the Visible and Infrared GOES-16 images, with the coldest IR brightness temperatures in the -80 to -89ºC range (shades of violet to purple) — and along the southern flank of the storms, inflow feeder bands were evident the Visible imagery. 00 UTC rawinsonde data from Del Rio, Texas (below) showed that parcel temperatures of -80 to -89ºC would indicate significant vertical overshoots of both the equilibrium level (-67ºC) and the tropopause (-74.7ºC).

Plot of rawinsonde data from Del Rio, Texas [click to enlarge]

Plot of rawinsonde data from Del Rio, Texas [click to enlarge]

Farther to the north, 1-minute GOES-16 Infrared images (below) showed other thunderstorms that produced large hail (up to 3.25 inches in diameter) in the Dallas/Fort Worth area after sunset.

GOES-16 “Clean” Infrared Window (10.35 µm) images, with SPC Storm Reports plotted in cyan [click to play animation | MP4]

GOES-16 “Clean” Infrared Window (10.35 µm) images, with SPC Storm Reports plotted in cyan [click to play animation | MP4]

Protocol changes to the CIMSS Direct Broadcast ftp website

April 27th, 2021 |

VIIRS True Color imagery and VIIRS M12 and M13 (3.7 µm and 4.05 µm) infrared imagery, 1716 UTC on 27 April 2021 (Click to enlarge)

There have been recent changes to web browsers with a result that ftp:// protocols are only rarely supported (and that can be with difficulty). Accordingly, ftp access to UW-Madison CIMSS Direct Broadcast imagery has been altered so that https:// protocols can be used. This can allow direct visualization of imagery through a web-browser, eliminating the need to download it first. To access NOAA-20 data, for example, start at https://ftp.ssec.wisc.edu/pub/eosdb/j01/ (similar urls access Suomi-NPP, Terra and Aqua imagery);  then select an instrument (VIIRS or ATMS, for example), a day/time, and the type of imagery. The imagery shown above came from much larger images at https://ftp.ssec.wisc.edu/pub/eosdb/j01/viirs/2021_04_27_117_1716/images/. It shows True Color imagery over the Gulf Stream just east of North Carolina’s Outer Banks, along with M12 (3.7 µm) and M13 (4.05 µm) imagery. There is both a color change and temperature change to the water as one travels across the North Wall of the Gulf Stream.

The CIMSS Direct Broadcast site is one of very few that allows access to imagery for all 22 VIIRS channels: 5 I-bands, 16 M-bands, and the Day Night band.

Three Rivers Fire in New Mexico

April 26th, 2021 |

GOES-17 Shortwave Infrared (3.9 µm) (top left), GOES-17 Fire Temperature RGB (top right), GOES-16 Fire Power (bottom left) and GOES-16 Fire Temperature (bottom right) [click to play animation | MP4]

GOES-17 Shortwave Infrared (3.9 µm) (top left), GOES-17 Fire Temperature RGB (top right), GOES-16 Fire Power (bottom left) and GOES-16 Fire Temperature (bottom right) [click to play animation | MP4]

1-minute Mesoscale Domain Sector GOES-17 (GOES-West) Shortwave Infrared (3.9 µm) and Fire Temperature RGB along with 5-minute  GOES-16 (GOES-East) Fire Power and GOES-16 Fire Temperature derived products (above) showed the thermal signature of the rapidly-growing Three Rivers Fire in New Mexico on 26 April 2021. The maximum GOES-17 Shortwave Infrared brightness temperature was 138.7ºC — which is the saturation temperature for those ABI detectors — every minute for a solid hour between 1901-2001 UTC. Peak GOES-16 Fire Power and Fire Temperature values during that time were in excess of 2960 MW and 2960 K, respectively. At nearby Ruidoso, southwesterly winds were gusting as high 39 knots.

GOES-16 True Color RGB images created using Geo2Grid (below) revealed 2 distinct “fire jump” events (after 20 UTC, and again after 22 UTC), when smoke/cloud material was ejected to higher altitudes than the primary smoke plume. In addition, southwest of the large smoke plume a smaller and more diffuse plume of blowing gypsum dust could be seen streaming northeastward from White Sands National Park.

GOES-16 True Color RGB images [click to play animation | MP4]

GOES-16 True Color RGB images [click to play animation | MP4]


Offshore transport of glacial silt from Southeast Alaska

April 25th, 2021 |

GOES-17 CIMSS Natural Color RGB images [click to play animation | MP4]

GOES-17 CIMSS Natural Color RGB images [click to play animation | MP4]

GOES-17 (GOES-West) CIMSS Natural Color RGB images (above) depicted a large offshore surge of airborne glacial silt from Southeast Alaska on 25 April 2021. During the preceding week, abnormally warm and dry conditions across much of Southeast Alaska (Juneau | Ketchikan | Sitka | Yakutat) promoted significant snow melt which exposed a great deal of surface glacial silt.

The leading edge of the aerosol could also be seen in GOES-17 Near-Infrared “Cirrus” (1.37 µm) images (below). The presence of a very dry air mass over the region (rawinsonde data: Yakutat | Annette Island) allowed some of the lower-tropospheric aerosol to be sensed by this spectral band.

GOES-17 Near-Infrared "Cirrus" (1.37 µm) images [click to play animation | MP4]

GOES-17 Near-Infrared “Cirrus” (1.37 µm) images [click to play animation | MP4]

GOES-17 True Color RGB images created using Geo2Grid (below) provided a clearer view of the areal coverage of glacial silt moving westward off the coast.

GOES-17 True Color RGB images [click to play animation | MP4]

GOES-17 True Color RGB images [click to play animation | MP4]

With ample illumination from the Moon (which was in the Waxing Gibbous phase, at 96% of Full),  the emergence of airborne particles off the Southeast Alaska coast was seen in a Suomi NPP VIIRS Day/Night Band (0.7 µm) image at 1221 UTC (below).

Suomi NPP VIIRS Day/Night Band (0.7 µm) image [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) image [click to enlarge]