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

As a strong cold front (surface analyses) moved southward from Colorado and Nebraska across New Mexico, Texas and Oklahoma on 28 November 2017, the subtle curved arc signature of a lee-side cold frontal gravity wave could be seen on GOES-16 Lower-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (above).

Closer views of imagery from each of the 3 water vapor bands are shown below.

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Himawari-8 Lower-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (above) showed a strong storm as it was rapidly intensifying south of the Aleutian Islands and moving into the Bering Sea during the 25-26 November 2017 period (surface analyses), producing hurricane force winds. Hourly surface wind gusts (knots) are plotted in red on the images.

GOES-15 (GOES-West) Visible (0.63 µm) images during the daylight hours of 25 and 26 November (below) offered a more detailed view of the storm. As with the water vapor images above, hourly surface wind gusts (knots) are plotted in red on the images.

A plot of hourly surface observations from Adak Island in the Aleutians is shown below. Peak wind gusts of 91 mph were reported on Adak Island and at Unalaska.

Aqua and Terra MODIS satellite imagery of #hurricane force low that has lashed the Bering Sea and Aleutian Islands for the past 36 hours. Buoy 46075 (pink star) measured phenomenal seas for several hours (circled), with significant wave heights peaking at 52.2 ft (15.9 m) #akwx pic.twitter.com/uYcdXkdkWN

— NWS OPC (@NWSOPC) November 27, 2017

Also of note: the surface pressure at St. Paul Island dropped to unusually low levels as the storm moved into the Bering Sea.

This morning’s altimeter pressure setting of 27.95″ at St. Paul Island, Alaska, is the 3rd lowest since 1949 at that station. [27.67 on Oct 25, 1977 & 27.82″ on Dec 26, 1973]. @AlaskaWx

— Brian Brettschneider (@Climatologist49) November 26, 2017

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

An eruption of Mexico’s Popocatépetl volcano — the largest since 2013 — occurred on 23 November 2017. The volcanic cloud was evident in GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) as it drifted southward. However, due to the relatively thin nature of the cloud (a result of low values of ash loading), 10.3 µm infrared brightness temperatures were quite warm (greater than -20ºC), making a height determination from the single-band infrared imagery alone rather difficult.

This example demonstrates the value of using multi-spectral image techniques to derive retrieved products — available from the NOAA/CIMSS Volcanic Cloud Monitoring site — such as Ash Height (below). In this case, the retrieved ash cloud height was 7 km or 24,000 feet (darker green enhancement0, even for portions of the cloud with relatively low ash loading.

During the following nighttime hours, another eruption occurred, this time sending ash to a slightly higher altitude of 8 km or 26,000 feet (below).

A GOES-16 GeoColor animation can be seen here.

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Two of the channels on GOES-16 detect radiation in parts of the electromagnetic spectrum where sulfur dioxide (SO2) absorbs radiation: Band 10 (7.3 µm, the low-level Water Vapor channel) and Band 11 (8.4 µm, the Infrared Cloud Phase channel, see in particular the figure on the first page of the Quick Guide). The SO2 Red-Green-Blue (RGB) Composite was designed to highlight volcanic plumes, using the Brightness Temperature Difference between the mid-level and low-level Water Vapor Channels (6.9 µm – 7.3 µm) as the Red Component, the Brightness Temperature Difference between the Clean Infrared Window (Band 13, 10.3 µm) and the Infrared Cloud Phase (Band 11, 8.4 µm) as the Green Component, and the Clean Infrared Window (Band 13, 10.3 µm) as the Blue Component.  The eruption is obvious in the SO2 RGB imagery, below, with magenta and blue values apparent.  The volcanic plume’s appearance differs markedly from that of the convection along the Pacific coast of Mexico south and west of the eruption.

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Satellites have the capability of allowing us to see things that may otherwise have gone unnoticed. The numerous bands available on #GOES16 shows an unusually shaped contrail over Barnes County ND, most noticeable in the water vapor bands. #ndwx #mnwx pic.twitter.com/OHqCF0bO6s

— NWS Grand Forks (@NWSGrandForks) November 21, 2017

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

As mentioned in a Tweet from NWS Grand Forks (above), an interesting contrail was seen over eastern North Dakota on 21 November 2017. They noted that the contrail was most easily seen using imagery from the water vapor bands.

A comparison of GOES-16 ABI Lower-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (below) showed the formation and motion of the contrail feature (which was likely caused by military aircraft, based in Grand Forks and/or Minot, performing training exercises).

A comparison of three of the GOES-16 Near-Infrared bands (below) showed that the high-altitude ice crystal contrail feature was also very apparent in “Cirrus” (1.37 µm) images; the contrails themselves were very subtle in the “Vegetation” (0.86 µm) and “Snow/Ice” (1.61 µm) images, but their darker shadows which were cast upon the surface (to the east-northeast) were more obvious — for example, on the 2132 UTC images.

A similar contrail feature was noted over North Dakota in March 2011.

 

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