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Snowfall across the Deep South

By Scott Bachmeier •

GOES-13 (GOES-East) Visible (0.63 µm) images (above) showed a broad swath of snow cover from Louisiana to Virginia on 09 December 2017. Some notable storm total accumulations included 6.5 inches at Kentwood, Louisiana, 7.0 inches at Bay Springs, Mississippi, 12.0 inches at Jacksonville, Alabama, 2.0 inches at Century, Florida, 18.0... Read More

GOES-13 Visible (0.63 µm) images [click to play animation]

GOES-13 Visible (0.63 µm) images [click to play animation]

GOES-13 (GOES-East) Visible (0.63 µm) images (above) showed a broad swath of snow cover from Louisiana to Virginia on 09 December 2017. Some notable storm total accumulations included 6.5 inches at Kentwood, Louisiana, 7.0 inches at Bay Springs, Mississippi, 12.0 inches at Jacksonville, Alabama, 2.0 inches at Century, Florida, 18.0 inches at Mountain City, Georgia, 7.0 inches near Roan Mountain, Tennessee, and 25 inches at Mt. Mitchell State Park, North Carolina. Daily record snowfall accumulations included a Trace at New Orleans, Louisiana, 5.1 inches at Jackson, Mississippi and 1 inch at Mobile, Alabama.

A closer view of GOES-13 visible images (below) showed the band of snow cover across Louisiana, Mississippi and Alabama. Much of the the snow melted quickly, due to warm ground temperatures and a full day of sun.

GOES-13 Visible (0.63 µm) images, with station identifiers plotted in yellow [click to play animation]

GOES-13 Visible (0.63 µm) images, with hourly surface reports plotted in yellow [click to play animation]

A more detailed view of the snow cover was provided by 250-meter resolution Terra and Aqua MODIS true-color Red-Green-Blue (RGB) images from the SSEC MODIS Direct Broadcast site (below). Note that snow cover was evident all the way to the Gulf Coast at Atchafalaya Bay, Louisiana early in the day.

Terra and Aqua MODIS true-color RGB images of the central Gulf Coast region [click to enlarge]

Terra and Aqua MODIS true-color images of the central Gulf Coast region [click to enlarge]

Terra and Aqua MODIS true-color RGB images, centered over Atchafalaya Bay, Louisiana [click to enlarge]

Terra and Aqua MODIS true-color RGB images, centered over Atchafalaya Bay, Louisiana [click to enlarge]

Terra and Aqua MODIS true-color images, centered over New Orleans, Louisiana [click to enlarge]

Terra and Aqua MODIS true-color images, centered over New Orleans, Louisiana [click to enlarge]

Terra MODIS true-color image, centered over Atlanta, Georgia [click to enlarge]

Terra MODIS true-color image, centered over Atlanta, Georgia [click to enlarge]

It is interesting to note that with the aid of reflected moonlight — the Moon was in the Waning Gibbous phase, at 59% of Full — the Suomi NPP VIIRS Day/Night Band (0.7 µm) was able to detect the area of deeper snow cover across southeastern Louisiana and southern Mississippi at 0741 UTC or 1:41 AM local time; this snow cover was then seen during the following morning on GOES-13 Visible (0.63 µm) imagery at 1440 UTC or 8:40 AM local time (below). A VIIRS instrument is part of the payload on the recently-launched JPSS-1/NOAA-20 satellite.

Suomi NPP VIIRS Day/Night Band (0.7 µm) and GOES-13 Visible (0.63 µm) images [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and GOES-13 Visible (0.63 µm) images [click to enlarge]

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Snowfall in southern Texas

By Scott Bachmeier •

The combination of lift from an upper-level trough and cold air behind the passage of a surface cold front  set the stage for accumulating snow across far southern Texas on 08 December 2017. As the clouds cleared, GOES-13 (GOES-East) Visible (0.63 µm) and Shortwave Infrared (3.9 µm) images (above) revealed a narrow swath of snow... Read More

GOES-13 Visible (0.63 µm, left) and Shortwave Infrared (3.9 µm, right) images, with hourly plots of surface reports [click to play animation]

GOES-13 Visible (0.63 µm, left) and Shortwave Infrared (3.9 µm, right) images, with hourly plots of surface reports [click to play animation]

The combination of lift from an upper-level trough and cold air behind the passage of a surface cold front  set the stage for accumulating snow across far southern Texas on 08 December 2017. As the clouds cleared, GOES-13 (GOES-East) Visible (0.63 µm) and Shortwave Infrared (3.9 µm) images (above) revealed a narrow swath of snow cover running northeastward from the Rio Grande River toward Corpus Christi — the highest snowfall total associated with this feature was 7.0 inches near Corpus Christi. Daily snowfall records included 0.3 inch at Brownsville and 1.0 inch at Corpus Christi.

A toggle between Terra MODIS true-color and false-color Red-Green-Blue (RGB) images from RealEarth (below) showed the southwestern portion of this band of snow cover (which appeared as darker shades of cyan in the false-color image).

Suomi NPP VIIRS true-color and false-color RGB images [click to enlarge]

Suomi NPP VIIRS true-color and false-color RGB images [click to enlarge]

Farther to the north, another southwest-to-northeast oriented band of snow cover was seen on Terra MODIS true-color and false-color RGB images (below), stretching from San Antonio to Austin to College Station. The highest snowfall total there was 5.0 inches (NWS Austin/San Antonio summary),

Terra MODIS true-color and false-color images [click to enlarge]

Terra MODIS true-color and false-color images [click to enlarge]

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Wildfires in southern California

By Scott Bachmeier •

GOES-15 (GOES-West) Shortwave Infrared (3.9 µm) images (above; also available as an animated GIF) showed the rapid development of wildfires driven by strong Santa Ana winds in Southern California on 05 December 2017. The fire thermal anomalies or “hot spots” are highlighted by the dark black to yellow to red pixels — the initial signature... Read More

GOES-15 Shortwave Infrared (3.9 µm) images, with hourly surface plots [click to play MP4 animation]

GOES-15 Shortwave Infrared (3.9 µm) images, with hourly surface plots [click to play MP4 animation]

GOES-15 (GOES-West) Shortwave Infrared (3.9 µm) images (above; also available as an animated GIF) showed the rapid development of wildfires driven by strong Santa Ana winds in Southern California on 05 December 2017. The fire thermal anomalies or “hot spots” are highlighted by the dark black to yellow to red pixels — the initial signature was evident on the 0230 UTC image (6:30 PM local time on 04 December), however the GOES-15 satellite was actually scanning that particular area at 0234 UTC or 6:34 PM local time. The Thomas Fire (the largest of the fires) advanced very quickly toward the southwest, nearly reaching the coast.

Nighttime image toggles between Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) data at 0904 UTC and 1044 UTC (below) revealed the large fire hot spots, along with the extensive smoke plume that was drifting over the adjacent nearshore waters of the Pacific Ocean. With ample illumination from the Moon (which was in the Waning Gibbous phase, at 95% of Full), the “visible image at night” capability of the VIIRS Day/Night Band — which will also be available from the recently-launched JPSS-1/NOAA-20 satellite — was clearly demonstrated.

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) images, with plots of surface reports [click to enlarge]

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) images, with plots of surface reports [click to enlarge]

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) images, with plots of surface reports [click to enlarge]

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) images, with plots of surface reports [click to enlarge]

A toggle between the two VIIRS Day/Night Band images (below; courtesy of William Straka, CIMSS) showed initial darkness resulting from fire-related power outages in Santa Barbara County to the north, and Ventura County to the south (in the Oxnard/Camarillo area).

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

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

This large wind-driven fire was also very hot — the maximum brightness temperature on the VIIRS 4.05 µm Shortwave Infrared image was 434.6 K or 322.6º F, which was above the saturation threshold of the VIIRS 3.75 µm Shortwave Infrared detectors (below).

Suomi NPP VIIRS 4.05 µm and 3.75 µm Shortwave Infrared images [click to enlarge]

Suomi NPP VIIRS 4.05 µm and 3.75 µm Shortwave Infrared images [click to enlarge]

In a comparison of daytime GOES-15 Visible (0.63 µm) and Shortwave Infrared (3.9 µm) images (below), the west-southwestward transport of smoke over the Pacific Ocean was clearly seen.

GOES-15 Visible (0.63 µm, top) and Shortwave Infrared (3.9 µm, bottom) images [click to play MP4 animation]

GOES-15 Visible (0.63 µm, top) and Shortwave Infrared (3.9 µm, bottom) images [click to play MP4 animation]

A more detailed view of the thick smoke originating from the 3 fires (from north to south: the Thomas, Rye and Creek fires) was provided by a 250-meter resolution Aqua MODIS true-color Red-Green-Blue (RGB) image from the MODIS Today site (below).

Aqua MODIS true-color RGB image [click to enlarge]

Aqua MODIS true-color RGB image [click to enlarge]

Immediately downwind of the Creek Fire, smoke was reducing the surface visibility to 1 mile at Van Nuys and adversely affecting air quality (below).

Time series plot of surface reports at Van Nuys, California [click to enlarge]

Time series plot of surface reports at Van Nuys, California [click to enlarge]

===== 06 December Update =====

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.75 µm and 4.05 µm) images [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.75 µm and 4.05 µm) images [click to enlarge]

The fires in Southern California continued to burn into the following night, as shown by Suomi NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.75 µm and 4.05 µm) images (above; courtesy of William Straka, CIMSS). A large-scale view with Day/Night Band imagery revealed the extent of smoke transport westward over the Pacific Ocean.

GOES-15 Shortwave Infrared (3.9 µm) images (below) displayed the thermal signatures exhibited by the fires. Note the appearance of a new fire — the Skirball Fire — first appearing on the 1300 UTC (5:00 AM local time) image, just north of Santa Monica (KSMO). Although the Santa Ana winds were not quite as strong as the previous day, some impressive wind gusts were still reported.

GOES-15 Shortwave Infrared (3.9 µm) images, with hourly surface plots [click to play MP4 animation]

GOES-15 Shortwave Infrared (3.9 µm) images, with hourly surface plots [click to play MP4 animation]

A toggle between 250-meter resolution Terra (1911 UTC) & Aqua (2047 UTC) MODIS true-color images from MODIS Today (below) showed significant pyrocumulus development from a flare-up along the northeast perimeter of the Thomas Fire. The cloud plume only exhibited a minimum infrared brightness temperature of +5.5º C on the corresponding Aqua MODIS Infrared Window image, far above the -40ºC threshold assigned to pyroCumulonimbus clouds.

Comparison of Terra (1911 UTC) & Aqua (2047 UTC) MODIS true-color RGB images [click to enlarge]

Comparison of Terra (1911 UTC) & Aqua (2047 UTC) MODIS true-color RGB images [click to enlarge]

===== 07 December Update =====

Suomi NPP Day Night Band Imagery, 3-7 December 2017, over southern California

RealEarth imagery of the Day Night Band over 5 days (one image each night from 3 through 7 December), above, shows the evolution of the fire complex (Imagery courtesy Russ Dengel, SSEC). Similarly, a closer view of daily composites of VIIRS Shortwave Infrared (3.74 µm) imagery (below) revealed the growth and spread of the Thomas Fire from 04-07 December.

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) image composites [click to enlarge\

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) image composites [click to enlarge]

In a toggle between Terra MODIS true-color and false-color RGB images (below), the large burn scar of the Thomas Fire (shades of red to brown) was very apparent on the false-color image.

Terra MODIS true-color and false-color images [click to enlarge]

Terra MODIS true-color and false-color images [click to enlarge]

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Supermoon VIIRS Day/Night Band imagery

By Scott Bachmeier •

The only Supermoon of 2017 occurred on 03 December — and a composite of Suomi NPP VIIRS Day/Night Band (0.7 µm) swaths viewed using RealEarth (above) demonstrated the “visible image at night” capability of that spectral band. A VIIRS instrument is also part of the payload on recently-launched JPSS-1/NOAA-20.A few... Read More

Composite of Suomi NPP VIIRS Day/Night Band swaths [click to enlarge]

Composite of Suomi NPP VIIRS Day/Night Band swaths [click to enlarge]

The only Supermoon of 2017 occurred on 03 December — and a composite of Suomi NPP VIIRS Day/Night Band (0.7 µm) swaths viewed using RealEarth (above) demonstrated the “visible image at night” capability of that spectral band. A VIIRS instrument is also part of the payload on recently-launched JPSS-1/NOAA-20.

A few examples providing closer looks using VIIRS Day/Night Band (DNB) imagery are shown below, beginning with the western portion of an Atlantic storm that had been producing Gale Force winds during the previous 6-12 hours.

Suomi NPP VIIRS Day/Night Band (0.7 µm) image centered over the western Atlantic [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) image centered over the western Atlantic [click to enlarge]

A toggle between Day/Night Band (0.7 µm) and Fog/stratus Infrared Brightness Temperature Difference (11.45 µm – 3.74 µm) images, centered over the Southeast US (below) showed widespread areas of fog and/or stratus The brighter fog/stratus features were generally brighter on the DNB image..

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Fog/stratus Infrared Brightness Temperature Difference (11.45 µm - 3.74 µm) images, centered over the Southeast US [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Fog/stratus Infrared Brightness Temperature Difference (11.45 µm – 3.74 µm) images, centered over the Southeast US [click to enlarge]

Another toggle between DNB and Fog/stratus Infrared Brightness Temperature Difference images, this time centered over Minnesota, Wisconsin and the UP of Michigan (below) revealed snow cover that was much below average for the date — especially across the UP of Michigan.

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Fog/stratus Infrared Brightness Temperature Difference (11.45 µm - 3.74 µm) images, centered over Minnesota and the UP of Michigan [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Fog/stratus Infrared Brightness Temperature Difference (11.45 µm – 3.74 µm) images, centered over Minnesota, Wisconsin and the UP of Michigan [click to enlarge]

Finally, a toggle between DNB images from consecutive overpass times (0935 and 1116 UTC), showing small clusters of rain showers moving inland along the coast of Oregon and far northern California (below). Because of the wide scan swath of the VIIRS instrument (2330 km), there are times when the same area will be imaged during 2 consecutive overpasses.

Suomi NPP VIIRS Day/Night Band images, centered off the coast of Oregon [click to enlarge]

Suomi NPP VIIRS Day/Night Band images, centered off the coast of Oregon [click to enlarge]

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