The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing.

The ABI on GOES-16 includes a Snow/Ice Channel at 1.61 µm and a Cirrus Channel at 1.38 µm. These bands offer different perspectives on the evolution of the atmosphere before and during the strong 13-14 March 2017 winter storm on the East Coast of the United States. The Snow/Ice channel, above, is dark in regions where ice clouds or snow on the ground are present because ice is a strong absorber of radiation with a wavelength of 1.61 µm. Water clouds, in contrast, readily reflect such radiation and appear brighter white. Consider the mp4 animation above (available here as a 150-megabyte animated gif). At the start of the animation, on 12 March, snow is indicated over Tennessee, a dark stripe that erodes on that day under the strong March sun. Cirrus retreating southward over the southeastern United States (cloud signals that are grey in the 1.61 µm imagery) reveal much brighter low-level stratus clouds (made of water droplets). Cirrus contrails are apparent above those low clouds. The Mesovortex over the Great Lakes is bright white — water clouds — and is gradually obscured by high-level cirrus clouds from the west and northwest. Terrain-induced wave clouds are also present over Pennsylvania. Their bright color suggests they are composed of water droplets.

On 13 March, low clouds are moving northward over the Piedmont of North Carolina and Virginia as Cirrus clouds spread northeastward from the Deep South. By 14 March, a well-developed wave cyclone is apparent with a large cirrus canopy outlining a warm conveyor belt.

What does the Cirrus Channel, below show? (Click here for a large animated gif.) Strong absorption by water vapor molecules occurs at 1.38 µm. Note, for example, that on 12 March the mesovortex is not apparent in the Cirrus Channel — but the wave clouds over Pennsylvania are. The conclusion is that the atmosphere over the northeast is much dryer than that over the western Great Lakes. On 13-14 March, lake-effect clouds are apparent downwind of Lake Superior in the Upper Peninsula of Michigan and over Wisconsin. The airmass has dried over the Upper Midwest in two days, allowing the Cirrus Channel to view features closer to the surface. In general, the cirrus channel provides outstanding delineation of cloud-top structures over the developing and mature extratropical cyclone.

The Cirrus Channel and the Snow/Ice Channel rely on reflected Solar energy to provide a signal. As such they are useful primarily during the day.

Added: Animations showing the evolution of the three GOES-16 Water Vapor bands during part of the East Coast storm’s lifecycle are available here. A water vapor animation from a CONUS perspective is available here. A better-quality animation centered over the northeast US is available here. Here is an animated gif/mp4 with 6.9 µm brightness temperatures and surface observations. A blog post on this storm is here.

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** The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. **

A Suomi NPP VIIRS Day/Night Band (0.7 µm) image (above) revealed the formative stage of a mesoscale vortex over Lake Michigan at 0740 UTC or 2:40 AM Central time on 12 March 2017.

During the subsequent daylight hours, GOES-16 Visible (0.64 µm) images (below) showed the continued development and motion of the mesovortex.

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2.5hr GOES-16 1min resolution animation of a meso-low over southern Lake MI this morning (Data is preliminary & non-operaitonal). pic.twitter.com/mJrmphY6SD

— NWS Marquette (@NWSMarquette) March 12, 2017

As was shown in a Tweet from NWS Marquette (above), beginning at 1741 UTC one of the GOES-16 Mesoscale Sectors was moved far enough northward to provide 1-minute imagery of the mesovortex (below; also available as an MP4 animation).

At South Haven, Michigan (KLWA), the surface visibility was reduced to 5 miles with light snow at 2014 UTC (below) as one of the more well-defined cloud elements associated with the mesovorex moved inland over that location.

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The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing.

Tweets on Tuesday 7 March 2017 highlighted the fast-moving fires over the High Plains (that began burning on 6 March), and they also highlighted different bands available from the GOES-16 ABI. For example, this tweet references the loop above, showing an animation of 3.9 µm temperatures; that shortwave infrared channel is used because it is more sensitive to hot temperatures than longer wavelength infrared channels. The Norman WFO also tweeted out imagery, shown below, that included the 0.86 µm ‘Veggie’ band and the 0.47 µm visible band. Why use those two channels?

The 0.47 µm imagery is observing a part of the visible electromagnetic spectrum where scattering is largest, so smoke plumes are more apparent at that wavelength than at 0.64 µm. For a very obvious event such as this one, this might not be as important, but for a modest fire event over Florida, shown next, it can be. The 0.86 µm imagery is useful because it very distinctly shows fire burn scars; that is, the contrast at 0.86 µm between vegetated soil and adjacent burned regions is greater than occurs at other visible wavelengths. That is shown in the toggle below that steps through 0.47 µm, 0.64 µm, 0.86 µm, 1.61 µm and 3.9 µm imagery for one time on 7 March. The smoke plume is most distinct at the shortest wavelength 0.47 µm; it is very difficult to discern at 0.86 µm and especially at 1.61 µm because these near-infrared channels sense radiation at longer wavelengths that is unaffected by scattering of light by the small smoke particles. Note, however, that the small lakes do jump out at both wavelengths because of the very different reflectance properties of land and water at both 0.86 µm and 1.61 µm.

Finally, compare the 0.64 µm and 0.86 µm with special focus on the burn scars (here is a toggle between the two). Although the spatial resolution is greatest in the 0.64 µm visible imagery (0.5 km at the sub-satellite point, vs. 1 km at the sub-satellite point for the 0.86 µm imagery), the burn scars nevertheless are more distinct at 0.86 µm, in part because vegetated ground is more reflective at 0.86 µm than at 0.64 µm (See the figure in ‘Tim’s Topics’ on page 2 of the 0.86 µm fact sheet).

=========================================================================A less extensive fire event occurred on 10 March 2017 in Florida. Focus on the largest hot spot (black pixels) in the 3.9 µm imagery in the center of the top third of the image below; this point is in southeastern Polk County. For this event, the smoke plume is more easily visualized in the 0.47 µm imagery than in the 0.64 µm or the 0.86 µm imagery. A burn scar does not appear in this case.

The GOES-R Website includes Fact Sheets for Band 1 (0.47 µm), Band 2 (0.64 µm), Band 3 (0.86 µm), Band 5 (1.61 µm) and Band 7 (3.9 µm).

AWIPS Note: The default enhancement (“IR_COLOR_CLOUDS_WINTER”) for 3.9 µm results in imagery that shows too little gradation over Florida during the daytime; for fire detection, either modify the colormap (this changed the temperature range from the default [-109 to 55] to -70 to 75, and is shown above) or switch to the”IR_COLOR_CLOUDS_SUMMER” enhancement.

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** The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. **

GOES-16 Visible (0.64 µm) images (above; also available as an MP4 animation) showed multiple undular bores over western Texas on 10 March 2017. The wave packets were perturbing the low-altitude fog and stratus clouds across the region during the morning hours, in advance of a cold front that was approaching from the north. One bore was moving toward the south, while another (apparently deeper) bore was moving toward the southwest.

A plot of 12 UTC rawinsonde data from Midland (below) revealed the presence of a strong low-level temperature inversion from the surface to the 850 hPa  pressure level — this inversion was acting to duct the gravity waves as they propagated southward and southwestward.

Even though the undular bores were relatively shallow features, a subtle signature of the southwestward-moving bore was seen in Middle-Level Water Vapor (6.9 µm) and Lower-Tropospheric (7.3 µm) images (be1ow).

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