Suomi NPP VIIRS 0.64 µm visible channel images

AWIPS II images of 375-meter resolution Suomi NPP VIIRS 0.64 µm visible channel data (above) showed the growth of new ice immediately offshore in the northwestern portion of Hudson Bay, Canada during the 17 November – 19 November 2013 time period. The northwesterly flow of cold arctic air in the Arviat, Nunavut (station identifier CYEK) region was also producing well-defined cloud streets over the open waters of Hudson Bay.

The corresponding false-color “Snow Cloud Discrimination” Red/Green/Blue (RGB) images (below) confirmed that the brighter white nearshore features seen on the visible images were ice — ice and snow cover appear as shades of red on the RGB images, in contrast to supercooled water droplet clouds which appear as varying shades of white.

Suomi NPP VIIRS “Snow Cloud DIscrimination” false-color RGB images

On 18 November, a significant amount of young pack ice motion can be seen in the 104-minute period between the 17:16 UTC and 19:00 UTC VIIRS visible images (below).

Suomi NPP VIIRS 0.64 µm visible channel images

Daily “stage of development” ice analyses from the Canadian Ice Service are shown below.

Canadian Ice Service daily ice analysis for northern Hudson Bay (17, 18, and 19 November)

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MODIS Visible (0.68 µm) and Infrared (11 µm) imagery from 1634 UTC 17 November overlain with hourly severe reports from 1700 and 1800 UTC (click to enlarge)

A late-season tornadic outbreak occurred on Sunday November 17th over the Upper Midwest. The animation above shows MODIS Imagery — visible and 11 µm just as the severe weather was erupting over Illinois. Two different sets of severe weather reports are overlain: those within an hour of the image, and those an hour after the image. The convection over central Illinois has just started to produce severe weather, and it intensified after the imagery (as seen by the blossoming in areal coverage of severe weather reports).

GOES-13 Enhanced Infrared (10.8 µm) imagery 17 November, times as indicated (click image to animate)

An animation of GOES-13 10.7 µm imagery (in RSO mode during the day), above, (also available here, on YouTube) shows the storms. The storm tops were not particularly cold (unsurprising given the date), but severe weather signatures (enhanced Vs, for example), can be discerned. Storm reports from SPC suggest that the strongest tornado, in Washington (in Tazewell County), was on the ground at 1700 UTC. The 1655, 1702 and 1710 UTC images shows a strong cell, but not one with particularly cold tops. An animation of these 3 images is shown below. The storm is relatively small compared to GOES-13 resolution. Note also that the storm appears to be north of Tazewell County because of parallax errors.

GOES-13 Enhanced Infrared (10.8 µm) imagery 17 November, times as indicated (click image to animate) Washington is in far northern Tazewell County, which County is outlined in White

The large-scale environment was unusually moist and unstable for November. Total Precipitable Water exceeded 200% of normal over much of the upper midwest (link), and an animation of GOES-13 Sounder imagery of DPI Lifted Index (link) showed instability, albeit in between holes in the cloud (the extensive cloud shields suggest that solar heating played little role in this outbreak). The 1700 UTC GOES DPI Lifted Index image is below. Lifted Indices below -5 are common throughout Illinois. (GOES-13 Sounder data continues to have missing data points, as noted here and here)

GOES-13 Sounder DPI Values of Lifted Index, 1700 UTC on 17 November (click image to enlarge)

Suomi/NPP also viewed the storms, but after they had moved east of Illinois. A toggle between VIIRS Visible, 11.35 µm and 1.61 µm imagery, below, shows isolated supercells pushing through the cirrus shield.

Suomi/NPP Visible (0.65 µm), Infrared (11.45 µm) and 1.61 µm imagery from 1913 UTC 17 November (click to enlarge)

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Suomi/NPP Imagery of Mt. Etna, including the Day/Night Band, I05 (11 µm) and M13 (3.9 µm) (click to play animation)

Mt. Etna, on Sicily in the Mediterranean Sea, erupted early in the morning on Nov 17th just before a Suomi/NPP overpass. The VIIRS Day/Night Band gives a clear view of the volcanic plume (and the light emitted by the lava in the caldera); thermal channels show a distinct hot spot: 360 K in the 11 micron channel, and 523 K in the 3.9 micron channel! (Imagery courtesy Will Straka, UW-Madison/CIMSS)

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GOES-15 0.63 µm visible channel images (click to play animation)

Hat tip to Mark Ruminski (NOAA/NESDIS) for directing our attention to a pair of airborne glacial silt plumes that were being drawn southward over the far northern Gulf of Alaska on 16 November 2013. McIDAS images of GOES-15 0.63 µm visible channel data (above; click image to play animation) showed the two distinct hazy plumes as they were being advected offshore east of the Cordova, Alaska (PACV) area. The tight cyclonic circulation of a mesoscale area of low pressure may have helped to increase the speed of the gap winds that were lofting the glacial silt particles from the Copper River Delta and Icy Bay regions.

Suomi NPP VIIRS 0.64 µm visible channel images

AWIPS images of Suomi NPP VIIRS 0.64 µm visible channel data (above) showed a better view of the 2 plumes at 21:23 and 23:04 UTC. The airborne glacial silt plumes appeared darker on the corresponding 3.74 µm shortwave IR images (below) due to enhanced solar reflection off the small particles.

Suomi NPP VIIRS 3.74 µm shortwave IR images

MODIS Volcanic Ash Height product

MODIS-based products designed to monitor volcanic ash plumes were also able to detect the glacial silt plumes and provide quantitative information about these features. The mean plume height (above) was around 5000 feet, with a maximum around 9000 feet at some locations. The mean particle effective radius (below) was generally in the 4-7 µm range, with a maximum size of 9-10 µm.

MODIS Volcanic Ash Particle Effective Radius product

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