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Melting snow cover across the High Plains and Midwest

By Scott Bachmeier •

GOES-16 (GOES-East) “Red” Visible (0.64 µm) and Day Cloud Phase Distinction Red-Green-Blue (RGB) images (above) revealed the rapid melting of parts of a broad swath of fresh snow cover (green in the RGB images) across the High Pains and Midwest on 17 April 2020. The snow melted quickly in central Nebraska (where storm totals were generally... Read More

GOES-16

GOES-16 “Red” Visible (0.64 µm) and Day Cloud Phase Distinction RGB images [click to play animation | MP4]

GOES-16 (GOES-East) “Red” Visible (0.64 µm) and Day Cloud Phase Distinction Red-Green-Blue (RGB) images (above) revealed the rapid melting of parts of a broad swath of fresh snow cover (green in the RGB images) across the High Pains and Midwest on 17 April 2020. The snow melted quickly in central Nebraska (where storm totals were generally less than 4 inches), but persisted in the Foothills of Colorado (where storm totals amounts of 10-20 inches were common).

A closer look at the eastern segment of the snow cover over eastern Nebraska, southern Iowa and northern Missouri (below) showed the effect of snow-cooled surfaces on suppressing the formation of cumulus clouds as diurnal heating increased into the afternoon hours. Surface air temperatures warmed into the upper 40s to low 50s F in areas where the snow melted — but were held in the upper 30s to low 40s F where deeper snow cover existed near the Iowa/Missouri border (where storm total amounts were as high as 12-16 inches).

GOES-16 Day Cloud Phase Distinction RGB images [click to play animation | MP4]

GOES-16 Day Cloud Phase Distinction RGB images [click to play animation | MP4]

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Wildfires near Chernobyl, Ukraine

By Scott Bachmeier •

Suomi NPP VIIRS Day/Night Band (0.7 µm), Near-Infrared (1.61 µm and 2.25 µm) and Shortwave Infrared (3.74 µm) images (above) showed visible and thermal signatures of a cluster of wildfires burning west of the abandoned Chernobyl nuclear power plant on 13 April 2020. The fire had reportedly burned about 8600... Read More

Suomi NPP VIIRS Day/Night Band (0.7 µm), Near-Infrared (1.61 µm and 2.25 µm) and Shortwave Infrared (3.74 µm) images (credit: William Straka, CIMSS) [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm), Near-Infrared (1.61 µm and 2.25 µm) and Shortwave Infrared (3.74 µm) images (credit: William Straka, CIMSS) [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm), Near-Infrared (1.61 µm and 2.25 µm) and Shortwave Infrared (3.74 µm) images (above) showed visible and thermal signatures of a cluster of wildfires burning west of the abandoned Chernobyl nuclear power plant on 13 April 2020. The fire had reportedly burned about 8600 acres during the previous week.

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Outbreak of severe thunderstorms across the Deep South

By Scott Bachmeier •

A major outbreak of severe thunderstorms (SPC Storm Reports) occurred across the Deep South on 12 April 2020. 1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed the development and propagation of deep convection during the 1200-2359 UTC period. The corresponding GOES-16 “Clean” Infrared Window (10.35 µm) images are shown below.Some of the strongest... Read More

GOES-16 "Red" Visible (0.64 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

A major outbreak of severe thunderstorms (SPC Storm Reports) occurred across the Deep South on 12 April 2020. 1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed the development and propagation of deep convection during the 1200-2359 UTC period. The corresponding GOES-16 “Clean” Infrared Window (10.35 µm) images are shown below.

GOES-16

GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

Some of the strongest long-track tornadoes occurred in southern Mississippi — a closer view of GOES-16 Visible, Infrared and Visible/Infrared Sandwich Red-Green-Blue (RGB) images (below) revealed the pulsing nature of overshooting tops — which exhibited cloud-top infrared brightness temperatures as cold as -77ºC at 2038-2039 UTC, about 35 minutes prior to the destructive tornado that moved through Bassfield — and well defined “enhanced-v” signatures were apparent in the Infrared and RGB imagery, with that signature’s warm wake immediate downwind (east) of the overshooting tops indicating the likely presence of Above-Anvil Cirrus Plumes.

GOES-16 "Red" Visible (0.64 µm ), "Clean" Infrared Window (10.35 µm), and Visible/Infrared Sandwich RGB images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm ), “Clean” Infrared Window (10.35 µm) and Visible/Infrared Sandwich RGB images [click to play animation | MP4]

GOES-16 "Red" Visible (0.64 µm) images, with time-matched SPC Storm Reports plotted in red [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) images, with time-matched SPC Storm Reports plotted in red [click to play animation | MP4]

1-minute GOES-16 Visible images (above) and Infrared images (below) include plots of time-matched SPC Storm Reports.

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

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

NOAA/CIMSS ProbSevere is a tool that could have been used during this outbreak to identify which radar cells were most likely to produce severe weather.  The image below, from here, shows the reports of severe weather, the warning polygons, and ProbSevere locations (a closer view of the Mississippi tornadoes can be seen here).

Severe weather reports from 12 April 2020 (Green: Hail; Blue: Wind; Red: Tornado), NWS Warning Polygons and ProbSevere locations (plotted as boxes when ProbSevere exceeded 50% (Click to enlarge)

===== 14 April Update =====

GOES-16

GOES-16 “Red” Visible (0.64 µm) and Normalized Difference Vegetation Index images [click to enlarge]

Southwest-to-northeast oriented tornado damage paths in southern Mississippi were evident in a toggle between GOES-16 Visible and Normalized Difference Vegetation Index (NDVI) images (above). NDVI values within the damage path were generally 0.6, compared to 0.7-0.8 in adjacent areas. According the the NWS Jackson storm survey, the maximum path width of the longest-track (~67 mile) EF-4 tornado that began near Bassfield was about 2 miles — the widest ever measured in Mississippi, and one of the widest tornado damage paths ever measured in the US.

In a toggle between Aqua MODIS NDVI and Land Surface Temperature (LST) images (below), LST values were 5-10ºF warmer — low 80s F, darker shades of red —  within the tornado damage path, compared to areas adjacent to the path.

Aqua MODIS Normalized Difference Vegetation Index and Land Surface Temperature images [click to enlarge]

Aqua MODIS Normalized Difference Vegetation Index and Land Surface Temperature images [click to enlarge]

The tornado damage paths were also apparent in a comparison of before (26 March) and after (14 April) Aqua MODIS True Color RGB images (below) from the MODIS Today site. Note that 2 smoke plumes were seen on the 26 March image.

Aqua MODIS True Color RGB images from 26 March and 14 April [click to enlarge]

Aqua MODIS True Color RGB images from 26 March and 14 April [click to enlarge]

True and False-color imagery from NOAA-20 (from this (temporary) website) also show the damage path.

True- and False-Color imagery from the afternoon NOAA-20 overpass on 14 April 2020 (Click to enlarge)

NOAA-20 True Color RGB imagery of the Mississippi EF-4 tornado damage path that had a maximum with of 2 miles is shown below, using RealEarth.

NOAA-20 VIIRS True Color RGB image, including county outlines and map labels [click to enlarge]

NOAA-20 VIIRS True Color RGB image, including county outlines and map labels [click to enlarge]

A StoryMap of this event in South Carolina, created by the NWS in Columbia SC, is here.

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Snow squalls across the Upper Midwest

By Scott Bachmeier •

The NWS Aberdeen forecast office issued a Snow Squall Warning on the morning of 09 April 2020 — and a sequence of GOES-16 (GOES-East) “Red” Visible (0.64 µm), “Clean” Infrared Window (10.35 µm) and Day Cloud Phase Distinction Red-Green-Blue (RGB) images (above) showed the southeastward movement of numerous convective cloud features responsible for the snow squalls. Cloud elements whose tops... Read More

GOES-16

GOES-16 “Red” Visible (0.64 µm), “Clean” Infrared Window (10.35 µm) and Day Cloud Phase Distinction RGB images [click to play animation | MP4]

The NWS Aberdeen forecast office issued a Snow Squall Warning on the morning of 09 April 2020 — and a sequence of GOES-16 (GOES-East) “Red” Visible (0.64 µm), “Clean” Infrared Window (10.35 µm) and Day Cloud Phase Distinction Red-Green-Blue (RGB) images (above) showed the southeastward movement of numerous convective cloud features responsible for the snow squalls. Cloud elements whose tops were glaciating exhibited shades of green in the RGB images; however, most cloud-top infrared brightness temperatures were generally rather warm (therefore lacking a color enhancement). No signatures of lightning were seen in GLM Flash Extent Density data with this shallow, low-topped convection. Of particular interest was the ~20 mile wide northwest-to-southeast oriented swath of fresh snowfall produced by these snow squalls, which passed through Aberdeen (KABR) and could be seen through gaps in the clouds on Visible (shades of white) and RGB images (shades of green); Aberdeen received 0.3 inch of snowfall.

Farther to the south and east, NWS Sioux Falls also issued a Snow Squall Warning — similar signatures of convective elements were seen in the GOES-16 imagery (below), including the glaciation of some of the cloud tops. Snowfall amounts were generally light (around 0.1 inch), but surface visibility was reduced to zero in some of the snow squalls.

GOES-16 "Red Visible (0.64 µm), "Clean" Infrared Window (10.35 µm) and Day Cloud Phase Distinction RGB images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm), “Clean” Infrared Window (10.35 µm) and Day Cloud Phase Distinction RGB images [click to play animation | MP4]

In addition, NWS Duluth issued a Snow Squall Warning; the corresponding GOES-16 imagery is shown below. Snowfall reports included 1.4 inches at Duluth (accumulating within 30 minutes) and 2.5 inches at Butternut, Wisconsin.

GOES-16 "Red Visible (0.64 µm), "Clean" Infrared Window (10.35 µm) and Day Cloud Phase Distinction RGB images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm), “Clean” Infrared Window (10.35 µm) and Day Cloud Phase Distinction RGB images [click to play animation | MP4]

It should be noted that these were the first Snow Squall Warnings issued by each of the 3 NWS forecast offices.



Important aspects of the boundary layer across the Upper Midwest were revealed by plots of rawinsonde data from Aberdeen, South Dakota and International Falls, Minnesota (below) — steep low-level lapse rates (surface – 3 km values of 7ºC per km) with ample moisture, and strong winds. The upper portion of the shallow convective layers were within the important -12 to -18ºC dendritic growth zone.

Plots of 12 UTC rawinsonde data from Aberdeen, South Dakota and International Falls, Minnesota [click to enlarge]

Plots of 12 UTC rawinsonde data from Aberdeen, South Dakota and International Falls, Minnesota [click to enlarge]

A time-lapse video of snow squalls that moved through Madison, Wisconsin can be seen here.

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