CIMSS Satellite Blog, CIMSS

Severe thunderstorms over Wyoming and South Dakota

By Scott Bachmeier • 28 June 2020

GOES-16 (GOES-East) “Red” Visible (0.64 µm) images with time-matched plots of SPC Storm Reports (above) displayed clusters of thunderstorms that moved across eastern Wyoming and western South Dakota on 28 June 2020. Numerous overshooting tops were seen, along with cloud-top gravity waves and a couple of Above-Anvil Cirrus Plumes (reference | VISIT training). These storms produced hail as large as 2.25″ in... Read More

GOES-16 “Red” Visible (0.64 µm) images, with SPC Storm Reports plotted in red [click to play animation | MP4]

GOES-16 (GOES-East) “Red” Visible (0.64 µm) images with time-matched plots of SPC Storm Reports (above) displayed clusters of thunderstorms that moved across eastern Wyoming and western South Dakota on 28 June 2020. Numerous overshooting tops were seen, along with cloud-top gravity waves and a couple of Above-Anvil Cirrus Plumes (reference | VISIT training). These storms produced hail as large as 2.25″ in diameter and wind gusts as high as 83 mph.

A longer sequence of GOES-16 “Clean” Infrared Window (10.35 µm) images that extended for several hours after sunset (below) showed that some overshooting tops exhibited cloud-top infrared brightness temperatures as cold as -70ºC (darker black enhancement).

GOES-16 “Clean” Infrared Window (10.35 µm) images, with SPC Storm Reports plotted in cyan [click to play animation | MP4]

The tropopause temperature in 00 UTC rawinsonde data from Rapid City, SD was -63ºC (below) — so the overshooting tops of -70ºC were likely about 1 km above the local tropopause / equilibrium level.

Plot of rawinsonde data from Rapid City, SD [click to enlarge]

Plot of 00 UTC rawinsonde data from Rapid City, SD [click to enlarge]

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Exploring the effects of GOES-17 parallax over Alaska

By Scott Bachmeier • 27 June 2020

GOES-17 (GOES-West) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (above) displayed the formation of an orographic rotor cloud downwind (north-northeast) of the Kigluaik and Bendeleben Mountains in the Seward Peninsula of Alaska on 27 June 2020. Even though the highest terrain in those mountain ranges was only 3700-4700 feet... Read More

Topography, GOES-17 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-17 (GOES-West) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (above) displayed the formation of an orographic rotor cloud downwind (north-northeast) of the Kigluaik and Bendeleben Mountains in the Seward Peninsula of Alaska on 27 June 2020. Even though the highest terrain in those mountain ranges was only 3700-4700 feet (1.1-1.4 km), the coldest cloud-top infrared brightness temperatures within the rotor cloud feature were around -50 to -51ºC.

A plot of rawinsonde data from Nome (below) showed the strong southwesterly winds that existed within most the troposphere on that day. The tropopause temperatures were around -51ºC at altitudes of 9.4-9.6 km — indicating that these high-altitude rotor clouds were forced by vertically-propagating waves initiated by interaction of the anomalously-strong southerly/southwesterly lower-tropospheric flow with the west-to-east oriented mountain ranges.

Plot of rawinsonde data from Nome, Alaska [click to enlarge]

Comparisons of topography and Visible/Infrared images from Suomi NPP and GOES-17 around 1320 UTC and 2140 UTC are shown below. Since there is generally very little parallax offset associated with imagery from polar-orbiting satellites (such as Suomi NPP), the rotor cloud appeared closer to the topography that helped to force development of that cloud feature.

Topography, Suomi NPP VIIRS Visible (0.64 µm) and GOES-17 “Red” Visible (0.64 µm) images around 1320 UTC [click to enlarge]

Topography, Suomi NPP VIIRS Infrared Window (11.45 µm) and GOES-17 “Clean” Infrared Window (10.35 µm) images around 1320 UTC [click to enlarge]

Topography, Suomi NPP VIIRS Visible (0.64 µm) and GOES-17 “Red” Visible (0.64 µm) images around 2140 UTC [click to enlarge]

Topography, Suomi NPP VIIRS Infrared Window (11.45 µm) and GOES-17 “Clean” Infrared Window (10.35 µm) images around 2140 UTC [click to enlarge]

Plots of GOES-17 parallax correction vectors and displacements (in km) for a 30,00-feet (9.1 km) cloud feature at select points over the Alaska region (from this site) are shown below. For such a cloud feature over the Seward Peninsula, the parallax offset would be about 40 km (25 miles) — which closely corresponded to the offset seen between the GOES-17 and Suomi NPP images shown above.

Plots of GOES-17 parallax correction vectors and displacements (in km) for a 30,000-foot (9.1 km) cloud feature at select points over the Alaska region [click to enlarge]

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Ice in Hudson Bay

By Scott Bachmeier • 25 June 2020

GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed the subtle motion of ice in the southwestern portion of Hudson Bay, Canada on 25 June 2020. A slower version of the animation is available here.According to the Ice Concentration Departure from Normal map issued by the Canadian Ice Service on 22 June (below),... Read More

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed the subtle motion of ice in the southwestern portion of Hudson Bay, Canada on 25 June 2020. A slower version of the animation is available here.

According to the Ice Concentration Departure from Normal map issued by the Canadian Ice Service on 22 June (below), except for the narrow sliver of above-normal nearshore ice, most of the ice coverage and concentration seen on the GOES-16 imagery was normal.

Ice concentration departure from normal [click to enlarge]

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Mesoscale Convective Vortex in Texas

By Scott Bachmeier • 23 June 2020

As a nocturnal Mesoscale Convective System dissipated over North Texas around sunrise on 23 June 2020, 1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) revealed a Mesoscale Convective Vortex (MCV) — which then aided the development of new thunderstorms across northeast Texas during the subsequent afternoon and evening hours.SPC Mesoscale Analysis products at 13 UTC and 16... Read More

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

As a nocturnal Mesoscale Convective System dissipated over North Texas around sunrise on 23 June 2020, 1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) revealed a Mesoscale Convective Vortex (MCV) — which then aided the development of new thunderstorms across northeast Texas during the subsequent afternoon and evening hours.

SPC Mesoscale Analysis products at 13 UTC and 16 UTC (below) showed that the MCV was moving into an environment characterized by low wind shear and instability — which helped the MCV persist as it moved eastward during the day.