Severe convection « CIMSS Satellite Blog

Severe thunderstorms exhibiting Above-Anvil Cirrus Plumes over the Dakotas

July 4th, 2020 | Scott Bachmeier

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed two severe thunderstorms along the North Dakota / South Dakota border region, which exhibited Above-Anvil Cirrus Plumes (reference | VISIT training).

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

A longer animation of GOES-16 Visible images with plots of time-matched SPC Storm Reports is shown above, with GOES-16 Infrared images shown below.

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

Pulsing overshooting tops were seen whose cloud-top infrared brightness temperatures were in the -70 to -78ºC range — according to a plot of 00 UTC rawinsonde data from Aberdeen, South Dakota (below), this represented a 1-2 km overshoot of the Most Unstable (MU) air parcel’s Equilibrium Level (EL).

Plot of 00 UTC rawinsonde data from Aberdeen, South Dakota [click to enlarge]

Several hours later, another thunderstorm that produced damaging winds in southwestern North Dakota exhibited a residual Above-Anvil Cirrus Plume in central North Dakota as the storm was dissipating, seen in Suomi NPP VIIRS Infrared Window (11.45 µm) and Day/Night Band (0.7 µm) images at 0915 UTC (below). Coldest cloud-top infrared brightness temperatures in the overshooting top region were in the -60 to -66ºC range, while within the warmer AACP feature extending eastward they were in the -52 to -55ºC range.

Suomi NPP VIIRS Infrared Window (11.45 µm) and Day/Night Band (0.7 µm) images [click to enlarge]

Posted in GOES-16, Severe convection, Suomi NPP, VIIRS | No Comments »

Severe thunderstorms over Wyoming and South Dakota

June 28th, 2020 | Scott Bachmeier

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]

Posted in GOES-16, Severe convection | No Comments »

Stereoscopic views of severe convection over Nebraska

June 8th, 2020 | Scott Lindstrom

GOES-16 (left) and GOES-17 (right) Band 2 (0.64 µm) Visible imagery, 2140 UTC on 8 June 2020 through 0130 UTC 9 June 2020

Strong convection developed over Nebraska late in the afternoon of June 8th (SPC Storm reports are here). Mesoscale domains from both GOES-16 and GOES-17 viewed this developing convection, enabling fine spatial and temporal-scale viewing of the convection. (Past Mesoscale domain sectors can be searched at this website; this website shows locations in the past year.)

The stereoscopic mp4 animation (created using geo2grid and ffmpeg; a similar blog post on this technique is here) above captures the convective development near 2200 UTC on the 8th, and follows the storm evolution through sunset. To view the imagery in three dimensions, cross your eyes until three images are present, and focus on the image in the middle.

A 2-panel comparison of GOES-17 and GOES-16 Visible images during the period 2230-0208 UTC is shown below, with time-matched plots of SPC Storm Reports. The images are displayed in the native projection of each satellite.

"Red" Visible (0.64 µm) images from GOES-17 (left) and GOES-16 (right) [click to play animation | MP4]

“Red” Visible (0.64 µm) images from GOES-17 (left) and GOES-16 (right), with SPC Storm Reports plotted in red [click to play animation | MP4]

Posted in GOES-16, GOES-17, Severe convection | No Comments »

Derecho in South Dakota

June 7th, 2020 | Scott Lindstrom

GOES-16 ABI Band 13 (10.3 µm) infrared imagery, 1901 6 June 2020 – 0656 7 June 2020 (Click to play mp4 animation)

Portions of the High Plains and intermountain states experienced a climatologically rare Derecho event oni 6-7 June 2020. (Here is a preliminary write-up on this event from the National Weather Service in Rapid City SD; the forecast office in Boulder discussed the event here.). The GOES-16 Clean window infrared (10.3 µm) animation, above, (Click here for the same animation as an animated gif) shows rapid development over western South Dakota late in the afternoon of 6 June. The swath of wind reports is shown in this graphic from the Storm Prediction Center.

Several satellite-based thermodynamic estimates keyed in on South Dakota as a region where instability was noteworthy. The GOES-16 All-Sky Convective Available Potential Energy (available here), shown below from 2026 UTC on 6 June when values were greatest, for example, showed a persistent corridor of instability across South Dakota.

GOES-16 ‘All-Sky’ estimates of Convective Available Potential Energy, 2026 UTC on 6 June 2020 (Click to enlarge)

NUCAPS estimates of 700-500 mb lapse rates, below (from this site), show pronounced instability upstream of South Dakota at 1945 UTC, when Suomi-NPP overflew the region. (Most of the soundings used to produce the lapse rate information were from successful infrared retrievals as shown in this graphic).

700-500 mb Lapse Rates derived from Suomi NPP NUCAPS soundings, 1945 UTC on 6 June 2020 (Click to enlarge)

Surface moisture had pooled over western South Dakota. That is shown in the plot below of surface dewpoints showing very unusual (for South Dakota) mid-60s dewpoints! Further evidence of the unusual moisture amounts over the high Plains (for early June) is in this sounding from Rapid City at 0000 UTC on 7 June (source); Precipitable Water is at 1.2″! This value is unusual for the location and time of year, as shown here (Source).

Surface Dewpoints, 2100 UTC on 6 June 2020 over South Dakota and surrounding states (Click to enlarge)

GOES-17 Full-Disk imagery (at 10-minute time-steps) captured an oblique view of the developing convection. (The ‘PACUS’ sector with 5-minute imagery terminates in west-central South Dakota so is not used here; A GOES-17 Mesoscale sector was not in place for this event, although a GOES-16 one was).