5-minute CONUS Sector GOES-19 (GOES-East) Nighttime Microphysics RGB + daytime True Color RGB images from the CSPP GeoSphere site (above) showed the formation of nocturnal river valley fog over parts of the Mississippi River and a few of its tributaries in Wisconsin, Minnesota, Iowa and Illinois on 03 August 2026. The river valley fog then dissipated within a few hours after sunrise. Light winds and cloud-free conditions within a surface ridge of high pressure over the region allowed for ample radiational cooling that led to the fog formation,

GOES-19 Night Fog brightness temperature difference (BTD) + daytime Visible images (below) included hourly plots of Ceiling and Visibility — at some sites in the Wisconsin River valley, the visibility dropped to 1/4 mile (or even to zero) at times.

A NOAA-21 VIIRS Day/Night Band image at 0833 UTC (3:33 AM Central Time) revealed a faint signature of the river valley fog (below), as illuminated by the Moon (which was in the Waning Gibbous phase, at 75% of Full).

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1-minute Mesoscale Domain Sector GOES-18 (GOES-West) Visible images with an overlay of the Fire Mask derived product (above) showed the Old Trails Fire (initially named the Euclid Fire) as it started around 1907 UTC on 01 August 2026 — then grew rapidly as strong SW winds (with gusts as high as 40 knots) caused the wildfire to quickly expand into northwestern portions of the Spokane, Washington area (forcing numerous evacuations). SPC had highlighted much of eastern Washington as having an Extreme Fire Risk on that day — and NWS Spokane issued its first-ever Particularly Dangerous Situation (PDS) Red Flag Warning for the area.

1-minute GOES-18 GeoColor RGB images with an overlay of Next Generation Fire System (NGFS) Fire Detection polygons (below) provided a better view of the thermal structure/intensity of wildfires in the Spokane area.

1-minute GOES-18 True Color RGB images from the CSPP GeoSphere site (below) displayed a larger-scale view of the smoke plumes produced by the Spokane area wildfires. A few intermittent pulses of brighter-white pyrocumulus clouds were seen immediately downwind of the Old Trails Fire.

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According to the Tokyo VAAC, Sheveluch (located on Russia’s Kamchatka Peninsula) erupted around 0508 UTC (text | image) on 31 July 2026. A signature of the resulting volcanic cloud became apparent in 10-minute Full Disk scan GOES-18 (GOES-West) Ash RGB images (above) and Dust RGB images (below), created using Geo2Grid. Brighter shades of yellow in both RGB image types were indicative of a mixture of ash and SO₂ within the volcanic cloud. The volcanic cloud signature eventually became lost within a band of meteorological clouds associated with a cold front south of the Aleutian Islands.

GOES-18 Split Cloud Top Phase images (below) included plots of Pilot Reports (PIREPs) and Volcanic Ash Advisory/Forecast polygons issued by the Anchorage VAAC. The 8.4 µm spectral band is sensitive to SO₂ absorption which led to positive values (brighter green to yellow to red) in the imagery.

As the volcanic cloud advanced farther eastward across the Bering Sea, advisory responsibility was transferred from the Tokyo VAAC to the Anchorage VAAC, beginning at 1500 UTC on 31 July (below). The leading, faster-moving portion of the volcanic cloud had a maximum altitude of FL340 (34000 feet) — while the trailing, slower-moving portion had a maximum altitude of FL250 (25000 feet).

Wile many aircraft were flying above the FL340 (34000 feet) maximum altitude of the leading portion of the volcanic cloud, there were some pilot reports of Volcanic Ash (VA) clouds either in the distance or below the altitude of the aircraft (below).

The final Anchorage VAAC advisory for this event was issued at 1209 UTC on 01 August (below), as the volcanic cloud was approaching the Washington VAAC area of responsibility.

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While the Pacific has kept seeing its share of intense tropical systems, the Atlantic has been quieter. This is consistent with what we expect with a strong El Niño, as the global scale impacts from that phenomenon tend to include increased wind shear in the Caribbean and western Atlantic which prevents storms in the tropics from intensifying and consolidating into cyclones. But we’re also seeing another major inhibitor of tropical cyclone development in large quantities of Saharan dust streaming off of north Africa into the skies over the eastern Atlantic. The air associated with these dust plumes is very dry, having originated over one of the largest and driest deserts on Earth. When this air is advected over the Atlantic, it mixes with the existing air and disrupts the development of any deep convection while also enhancing local wind shear. The radiative impact of the dust also stabilizes the atmosphere by absorbing solar energy above the surface while preventing warming at the surface, thus increasing the strength of the trade wind inversion and further limiting the vertical growth that is critical for hurricane formation and maintenance.

Since we’re interested in an African phenomenon, the geostationary satellites operated by EUMETSAT are going to be well-positioned to investigate this. The Flexible Combined Imager (FCI) on the geostationary Meteosat 12 plaform captured the following true color animation of the brown dust stretching hundreds of miles off of the shore of Africa and into the Atlantic air. FCI, like the Himawari Advanced Himawari Imager (AHI) has true red, green, and blue channels and is thus able to depict and event like this with chromatic fidelity. This animation was made on the EUMETSAT’s Eumetview site.

Of course, dust has different radiative properties than clear or cloudy air does, and with the numerous channels on the FCI, we can exploit those differences to create a Dust RGB product that highlights the position of the dust. Here’s the same period and time window as the true color animation above, but this time see how the dust can be made visually distinct from its surroundings through the application of infrared channel differences. The full recipe is given in the Dust RGB Quick Guide from EUMETSAT. Here, the purple and magenta colors represent the locations of the dust. Note how this product is even able to distinguish between a dust storm on the Algeria/Mali border (the bright magenta on the right side of the animation) from the surrounding desert; this is almost impossible to see in the true color loop above. The Dust RGB uses only infrared channels (including differences between different infrared channels) so it can be used 24 hours a day without issue.

Dust in the air, of course, means an increase in the optical depth. As this dust streams westward, it emerges into the field of view of the GOES-19 (GOES East) Advanced Baseline Imager (ABI). Here’s an animation from CSPP Geosphere that shows the Level 2 Aerosol Optical Depth product from the CSPP Geo software suite. This view shows data on the curved surface of the earth, with northern South America in the bottom left and western Africa curving away from the viewer in the middle. The dust can be seen as the bright colors at the center of the animation. As the day goes on, clouds in the dust region grow and thicken. Since the aerosol optical depth product is a clear sky and daytime only product, this results in increasing areas of the loop showing no data.

Finally, we can use VIIRS to take a very high resolution view of the dust. Unlike geostationary satellites which are fixed to specific locations, NOAA’s polar orbiting satellites roam the entire planet. Here’s a true color view from NOAA-21. The 375 m spatial resolution of the raw visible-wavelength channels enables ultra-detailed views of the dust, as can be seen in this image of the Atlantic between the Cap-Vert peninsula that is home to Dakar, Senegal on the right and the islands of Cabo Verde on the left.

These dust plumes aren’t uncommon this time of year, and have even been known to make their way all the way to the continental United States where they can affect everything from air quality to the beauty of the sunsets.

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