The GOES-13 Satellite, operational as GOES-East from April 2010 through December 2017 (with a notable interruption) will be turned off sometime after 1500 UTC on Wednesday 3 January 2018. (Update: due to an impending East Coast winter storm, GOES-13 deactivation was postponed to 8 January)

The visible Full Disk image above, from 1745 UTC on 2 January 2018, is one of the last fully illuminated visible image the satellite will process.  (The first processed full disk visible image, from 22 June 2006, can be viewed here.)

On 28 December 2017, GOES-13 imagery included a view of the Moon, as shown here (and zoomed in here).  Future GOES-East imagery from GOES-16 will not include images of the Moon.  GOES-16 will scan the moon when it is near the horizon (and there are occasional GOES-16 mesoscale sectors placed over the Moon for calibration purposes).  However, GOES-16 imagery is remapped to Earth points before being broadcast to the public.  The Moon (happily) is not on the Earth and its points will not be remapped.

Thank you GOES-13 for your long years of service.  A full-resolution version of the image above is available here.

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The very cold and dry airmass over the eastern half of the United States during early January 2018 is mostly devoid of water vapor, a gas that, when present, absorbs certain wavelengths of radiation that is emitted from the surface (or low clouds). That absorbed energy is then re-emitted from higher (colder) levels. Typically, surface features over the eastern United States are therefore not apparent. When water vapor amounts in the atmosphere are small, however, surface information can escape directly to space, much in the same way as occurs with (for example) the Clean Window channel (10.3 µm) on GOES-16 (water vapor does not absorb energy with a wavelength of 10.3 µm). The low-level water vapor (7.3 µm) image above, from near sunrise on 2 January 2018, shows many surface features over North and South Carolina, Kentucky, Tennessee and southern Illinois. The features are mostly lakes and rivers that are markedly warmer than adjacent land. (In fact, Kentucky Lake and Lake Barkely in southwest Kentucky are also visible in the 6.9 µm imagery!)

GOES-16 Weighting Functions (Click here ) describe the location in the atmosphere from which the GOES-16 Channel is detecting energy.  The upper-level (6.2 µm) and mid-level (6.95 µm) weighting functions show information originating from above the surface.  Much surface information is available at Greensboro, with smaller proportional amounts at Davenport and Lincoln.

The “Cirrus” Channel on GOES-16’s ABI (Band 4, 1.38 µm) also occupies a spot in the electromagnetic spectrum where water vapor absorption is strong.  Thus, reflected solar radiation from the surface is rarely viewed at this wavelength.  The toggle below, between the ‘Veggie’ Channel (0.86 µm) and the Cirrus Channel (1.38 µm) shows that some surface features — for example, lakes in North Carolina — are present in the Cirrus Channel.

Whenever the atmosphere is exceptionally dry, and skies are clear, check the water vapor channels on ABI to see if surface features can be viewed. A few examples of sensing surface features using water vapor imagery from the previous generation of GOES can be seen here.

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Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images (above) showed a well-defined Chesapeake Bay “streamer” cloud  at 0710 UTC or 3:10 AM local time on 01 January 2018. This cloud feature resulted from the flow of unusually-cold air over the relatively warm water of the bay — a process identical to that which produces the more common “lake effect” cloud bands. With the benefit of ample illumination from a Full Moon, the “visible image at night” capability of the Day/Night Band was vividly illustrated (and a VIIRS instrument on the JPSS series of satellites — including the recently-launched NOAA-20 — will provide similar imagery).

During the subsequent daylight hours, 1-minute Mesoscale Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (below) showed the Chesapeake Bay streamer cloud moving southward. Note that this cloud produced light snow as far south as Currituck, North Carolina (KOTX) from 14-15 UTC or 10-11 AM local time. It is possible that some light snow also occurred across a portion of the Eastern Shore of Virginia and the Outer Banks of North Carolina, but verification is not possible due to the scarcity of surface observation sites in those areas.

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GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed a well-defined mesoscale vortex (or “mesovortex”) moving southward across southern Lake Michigan on 31 December 2017. The default western GOES-16 Mesoscale Sector provided images at 1-minute intervals. This feature was responsible for brief periods of heavy snow at locations such as South Haven, Michigan KLWA (beginning at 1455 UTC), Benton Harbor, Michigan KBEH (beginning at 1625 UTC) and La Porte, Indiana KPPO (from 2055 to 2115 UTC).

Comparisons of POES AVHRR/Terra MODIS/Suomi NPP Infrared (10.8 µm/11.0 µm/11.45 µm) and Visible (0.86 µm/0.65 µm/0.64 µm) images along with an overlay of the corresponding Real-Time Mesoscale Analysis (RTMA) surface winds (below) provided views of the mesovortex at 1522 UTC, 1714 UTC and 1852 UTC, respectively.

During the preceding nighttime hours, a comparison of Suomi NPP VIIRS Infrared (11.45 µm) and Day/Night Band (0.7 µm) images at 0729 UTC along with an overlay of 07 UTC RTMA surface winds (below) showed in spite of patchy thin cirrus clouds over the region, ample illumination from the Moon (which was in the Waxing Gibbous phase, at 96% of Full) enabled a signature of the early stage of mesovortex formation to be seen on the Day/Night Band (DNB) image. Ice crystals within the thin cirrus clouds were responsible for the significant scattering city light signatures on the DNB image.

As an aside, it is interesting to note that ice could be seen in the nearshore waters of Lake Michigan — both in the western part of the lake, off the coast of Wisconsin and Illinois, and in the eastern part of the lake off the coast of Lower Michigan. The lake ice appeared as darker shades of cyan in the 250-meter resolution Terra MODIS false-color (Band 7-2-1 combination) Red-Green-Blue (RGB) image from the MODIS Today site (below).

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