GOES-17 Data shown in this post are preliminary and non-operational!

A Strong thunderstorm developed over Nebraska on 15 August (read more below), depositing baseball-sized hail in Arthur County. This storm was sampled by a GOES-16 Mesoscale sector, and the 1-minute imagery allowed views of the rotating updraft (Link). The stereoscopic view above, from the GOES-16 and GOES-17 CONUS sectors, shows the development and evolution of the storm at 5-minute increments (Click here for animated gif). To view the storm in three dimensions, cross your eyes until you view 3 images, and focus on the image in the middle. This storm develops the above-anvil cirrus plume that has been shown to be associated with severe weather, as in this case.

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1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed the development of thunderstorms which produced large hail and damaging winds across parts of southwestern South Dakota and western/central Nebraska (SPC Storm Reports) on 15 August 2018. The dominant storm in Nebraska exhibited a well-defined Above Anvil Cirrus Plume (AACP), which is often an indicator of a storm producing severe weather such as tornadoes, large hail or damaging wind (reference). Also note the slow-moving parallel bands of boundary layer wave clouds or “billow clouds” in northwestern Nebraska — this is a signature of warmer air flowing along the top of a low-level temperature inversion (caused by a pool of cold outflow from earlier thunderstorms). A stereoscopic view of this convection (using GOES-16 and GOES-17 visible images) can be seen here.

The corresponding GOES-16 Mid-level Water Vapor (6.9 µm) images (below) better revealed the broad circulation of a middle-tropospheric low that was centered over South Dakota (500 hPa analysis).

GOES-16 “Clean” Infrared Window (10.3 µm) images (above) showed that the coldest cloud-top infrared brightness temperatures associated with thunderstorm overshooting tops were around -60ºC (darker red enhancement) — slightly warmer than that of the tropopause on rawinsonde data from North Platte, Nebraska (below).

Regarding the AACP feature, in this case the plume was colder than the adjacent underlying thunderstorm anvil, as seen in a toggle between GOES-16 Visible and Infrared images at 0005 UTC — when the storm produced a wind gust of 70 mph at the surface (below). The temperature profile and lapse rate of the upper tropospheric/lower stratospheric air directly above the thunderstorm overshooting top will have an influence on whether an AACP is warmer or colder than the underlying thunderstorm anvil surface.

Finally, when trying to correlate the location of storm-top satellite image features with reports of hail/wind/tornadoes at the surface, it is important to factor in the effect of parallax. The GOES-16 satellite (positioned over the Equator at 75.2º W longitude) viewing angle for the North Platte area is 54 degrees — which has the effect of shifting the apparent location of storm-top features to the northwest of their true location over the Earth’s surface. The pair of image toggles shown below demonstrate how the “parallax-corrected” (northwest-shifted) location of the hail or wind reports more closely aligns with the cold overshooting top (orange to red enhancement) associated with the strongest storm updraft at that time.

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* GOES-17 images shown here are preliminary and non=operational *

A comparison of GOES-15 (GOES-West), GOES-14, GOES-17 and GOES-16 (GOES-East) Shortwave Infrared (3.9 µm) images (above) showed the thermal anomaly or “hot spot” (dark black to red pixels) associated with the Carr Fire in northern California on 11 August 2018. A GOES-16 Mesoscale Domain Sector was providing images at 1-minute intervals. This comparison demonstrates how fire detection can be affected by both satellite viewing angle and shortwave infrared detector spatial resolution (4 km at satellite sub-point for the GOES-14/15 Imager, vs 2 km for the GOES-16/17 ABI).

A toggle between 30-meter resolution Landsat-8 False Color and Thermal Infrared (10.9 µm) imagery viewed using RealEarth (below) showed new fire activity (clusters of red pixels) along the northeastern edge of the Carr Fire burn scar on the False Color image, as well as smoke plumes drifting northeastward; the heat signatures (brighter white pixels) of smaller fires hidden by the smoke were more clearly ssen on the Thermal Infrared image. As of this date the Carr Fire was the 8th largest and 6th most destructive fire on record in California, and was responsible for 8 fatalities.

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Numerous wildfires burning in southwestern Canada (primarily British Columbia: NOAA HMS fire/smoke product) produced large amounts of smoke, which was subsequently transported eastward across southern Canada and then southward across the Midwestern US during the 09 August – 11 August 2018 period. GOES-16 (GOES-East) Natural Color Red-Green-Blue (RGB) images from the AOS site (above) showed this smoke, portions of which were optically very thick at times (and were able to cast shadows owing to its significant vertical depth).

On 09 August the smoke was most highly concentrated over the Dakotas, as shown in a comparison of GOES-16 Aerosol Optical Depth (AOD), Smoke Detection, “Blue” Visible (0.47 µm) and “Red” Visible (0.64 µm) images (below). While much of the smoke was likely aloft within the middle troposphere, some had been mixed downward into the boundary layer and was restricting the surface visibility to 3-5 miles at many locations.

Note that the hazy signature of the widespread smoke was a bit more apparent in the 0.47 µm Visible imagery than the 0.64 µm Visible imagery, especially during mid-day when the sun-satellite “forward scattering angle” was at a minimum. The AOD and Smoke Detection derived products use data from Visible and Near-Infrared bands — so it they are only available during daytime hours (and only at solar zenith angles less than 60 degrees). The Smoke Detection product was more effective during times of enhanced forward scattering (early and late in the day) — but it also was susceptible to false alarms due to solar reflectance off water surfaces. Additional information on GOES-R Aerosol Detection Products in AWIPS is available here and here.

On 10 August, the smoke was most dense across the eastern Dakotas and Minnesota (below) — and once again, surface visibilities were restricted to 3-5 miles at some locations. On this day pilot reports mentioned flight visibility being restricted to 3 miles at altitudes as high as 12,000 feet.

Finally, on 11 August a north-to-south plume of particularly dense smoke drifted southward across Minnesota and Iowa, as seen in a comparison of GOES-16 Aerosol Optical Depth, “Red” Visible (0.64 µm). Near-Infrared “Cirrus” (1.37 µm) and “Clean” Infrared Window (10.3 µm) images (below). In this case the AOD values were quite high (in excess of 3.0 in northwestern Minnesota), beyond the range of values scaled for display in AWIPS — this led to the swath of black “No Data” values where the smoke was most dense. This plume of thick smoke also exhibited a signature in Near-Infrared “Cirrus” images; higher concentrations of airborne particles that are effective scatterers of light at the 1.37 µm wavelength (such as ice crystals, smoke, volcanic ash, or dust) will be detected using this imagery. Note the lack of a well defined signature on the 10.3 µm imagery — smoke is effectively transparent to radiation at these longer infrared wavelengths.

On a side note, the north-south plume of dense smoke over southcentral Canada and the Midwest US on 11 August was also very apparent from a distance of 983,269 miles (1,582,418.07 km) — 44 times the distance of the GOES-16 satellite — in EPIC Natural Color imagery from the DSCOVR satellite (below).

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