Severe Thunderstorms with Above-Anvil Cirrus Plumes over Texas

March 22nd, 2019 |

GOES-16 "Clean" Infrared Window (10.3 µm) images, with SPC storm replorts plotted in cyan [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm, left) and “Clean” Infrared Window (10.3 µm, right) images, with SPC storm reports plotted in red/cyan [click to play animation | MP4]

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images before sunset (above) and Infrared images after sunset (below) revealed Above-Anvil Cirrus Plume (AACP) features associated with severe thunderstorms that were producing large hail (SPC storm reports) over the Texas Panhandle on 22 March 2019.

GOES-16

GOES-16 “Clean” Infrared Window (10.3 µm) images, with SPC storm reports plotted in cyan [click to play animation | MP4]

A plot of 00 UTC rawinsonde data from Amarillo, Texas (below) showed that the Equilibrium Level (EL) and the tropopause was around 11 km — where the air temperature was near -60ºC, which is highlighted by a red enhancement on the Infrared imagery.  The calculated Maximum Parcel Level was around 13 km — where the air temperature was near -50ºC, which is highlighted by a yellow enhancement on the Infrared imagery; the MPL was the likely altitude of the AACP. Note on the 0245 UTC and 0258 UTC images that two of the hail reports were located near the colder (darker red to black) pixels of overshooting tops, which were close to the southern end of the warmer (brighter yellow) pixels of the AACP.

Plot of 00 UTC rawinsonde data from Amarillo, Texas [click to enlarge]

Plot of 00 UTC rawinsonde data from Amarillo, Texas [click to enlarge]

As pointed out on the Satellite Liaison Blog, some of the accumulating hail remained on the ground during the overnight hours — and the next morning, a hail swath signature was evident on GOES-16 Visible and Near-Infrared “Snow/Ice” (1.61 µm) imagery (below); the longest swath stretched for a distance of about 40 miles. The hail appeared as shades of white in the Visible imagery, and as darker shades of black in the Snow/Ice imagery (since ice is a strong absorber of radiation at the 1.61 µm wavelength). Note how the darker signature of wet soil (water is also a strong absorber at 1.61 µm) persisted on Near-Infrared  imagery even after the brighter signature of the melting hail swath disappeared on Visible imagery. Accumulating hail occurred over portions of Interstate 27 between Amarillo and Canyon, and Interstate 40 between Wildorado and Bushland; one trained storm spotter reported that the hail was several inches deep just northwest of Amarillo (Local Storm Reports).

GOES-16 "Red" Visible (0.64 µm) and Near-infrared "Snow/Ice" (1.61 µm) imagery [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and Near-infrared “Snow/Ice” (1.61 µm) imagery [click to play animation | MP4]

As the morning sun was beginning to warm the soil, GOES-16 Land Surface Temperature images at 1402 and 1502 UTC or 9:02 and 10:02 AM local time (below) depicted temperatures up to 10ºF cooler within the hail swath compared to adjacent bare ground.

GOES-16 Land Surface Temperature product at 1402 and 1502 UTC [click to enlarge]

GOES-16 Land Surface Temperature product at 1402 and 1502 UTC [click to enlarge]

With ample illumination from the Moon (in the Waning Gibbous phase, at 92% of Full) a “visible image at night” was provided by the Suomi NPP VIIRS Day/Night Band (0.7 µm), which showed the hall swath at 0748 UTC or 2:48 AM local time — a toggle between that Day/Night Band image and an early morning GOES-16 Visible image is shown bellow.

Suomi NPP VIIRS Day/Night Band (0.7 µm) image at 0748 UTC and GOES-16 "Red" Visible (0.64 µm) image at 1427 UTC [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) image at 0748 UTC and GOES-16 “Red” Visible (0.64 µm) image at 1427 UTC [click to enlarge]

Above-Anvil Cirrus Plume (AACP) over Argentina

November 3rd, 2018 |

An Above-Anvil Cirrus Plume (AACP) was observed over northern Argentina on 03 November 2018 during the RELAMPAGO-CACTI field experiment — radar indicated that the plume was 2-3 km above the top of the main thunderstorm anvil. A comparison of GOES-16 (GOES-East) “Red” Visible (0.64 µm), Near-Infrared “Snow/Ice” (1.61 µm) and “Clean” Infrared Window (10.3 µm) images (below) showed that the plume exhibited a colder appearance compared to the underlying anvil (which is explained by the temperature profile from 12 UTC Cordoba rawinsonde data). GOES-16 was actually scanning the AACP at 14:38:41 UTC — very close to the time of the radar image. The plume-producing thunderstorm was located south of Cordoba (identifier SACO).

GOES-16 "Red" Visible (0.64 µm), Near-Infrared "Snow/Ice" (1.61 µm) and "Clean" Infrared Window (10.3 µm) images [click to enlarge]

GOES-16 “Red” Visible (0.64 µm), Near-Infrared “Snow/Ice” (1.61 µm) and “Clean” Infrared Window (10.3 µm) images [click to enlarge]

Animations of GOES-16 Visible vs Snow/Ice and Visible vs Infrared are shown below. The southern storm also produced a smaller AACP at 1445 UTC.

GOES-16 "Red" Visible (0.64 µm), Near-Infrared "Snow/Ice" (1.61 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images [click to play animation | MP4]

GOES-16 "Red" Visible (0.64 µm) and "Clean" Infrared Window (10.3 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images [click to play animation | MP4]

Views of the convection across that region were provided by Terra MODIS (1457 UTC), Aqua MODIS (1736 UTC), Suomi NPP VIIRS (1742 UTC) and NOAA-20 VIIRS (1832 UTC) True Color Red-Green-Blue (RGB) images from RealEarth (below)True Color RGB images from Terra MODIS (1457 UTC), Aqua MODIS (1736 UTC), Suomi NPP VIIRS (1742 UTC) and NOAA-20 VIIRS (1832 UTC) [click to enlarge]

True Color RGB images from Terra MODIS (1457 UTC), Aqua MODIS (1736 UTC), Suomi NPP VIIRS (1742 UTC) and NOAA-20 VIIRS (1832 UTC) [click to enlarge]

Moisture Changes as viewed in the Cirrus Channel

March 14th, 2018 |

GOES-16 ABI Band 3 (0.86 µm) Reflectance, hourly from 1632-1932 UTC on 14 March 2018 (Click to enlarge)

Skies were clear over much of the southern Plains on 14 March 2018, as noted in the animation above that shows hourly GOES-16 ABI Channel 3 (0.86 µm) Imagery. Differences in absorption/reflectance between water and land yield excellent discrimination between lakes and land over Oklahoma and adjacent states.  GOES-16 ABI “Cirrus Channel” (Band 4, at 1.38 µm) shows little reflectance in the area over Oklahoma, except where cirrus clouds are present over western Oklahoma.  The rest of Oklahoma is dark because water vapor in the atmosphere is absorbing energy at 1.38 µm. An animation — also at hourly intervals — is shown below.  This uses the default enhancement in AWIPS, with reflectance values between 0 and 50 shown.

GOES-16 ABI Band 4 (1.37 µm) Reflectance, hourly from 1632-1932 UTC on 14 March 2018 with default AWIPS Enhancement (Click to enlarge)

If you alter the Band 4 enhancement to change the bounds from 0-50 (the default) to 0-2 (!), as was done in the animation below showing data every 5 minutes, a gradient in reflectance becomes apparent, and surface features — specifically lakes — over central Oklahoma that are initially present slowly become obscured as the gradient moves to the east. This gradient shows differences in moisture. The atmosphere that is moving into eastern Oklahoma from central Oklahoma is slightly more moist.  (Compare the morning sounding at Amarillo, for example, with a total precipitable water of 0.38″ to the morning sounding at Little Rock, with a total precipitable Water of 0.14″)

GOES-16 ABI Band 4 (1.37 µm) Reflectance, from 1632-1947 UTC on 14 March 2018 with default AWIPS Enhancement modified as described in text (Click to animate)

GOES-16 data includes channel differences and level 2 products that also confirm the slow increase in moisture. The Split Window Difference field, shown below with the default enhancement (Click here to see the same animation with the Grid MidRange Enhanced enhancement), and the Total Precipitable Water, at bottom, show a slow increase in moisture. These increases were above the surface: surface dewpoints in this region (source) were not increasing greatly.

Split Window Difference (10.3 µm – 12.3 µm) from 1632 – 1947 UTC on 14 March (Click to enlarge)

GOES-16 Total Precipitable Water Baseline Product, 1632-1947 UTC on 14 March 2018 (Click to enlarge)

Isolated cirrus cloud feature over Louisiana

November 10th, 2017 |

GOES-16 Visible (0.64 µm) images, with surface station identifiers plotted in yellow [click to play MP4 animation]

GOES-16 Visible (0.64 µm) images, with surface station identifiers plotted in yellow [click to play MP4 animation]

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

An isolated cloud feature moving east-southeastward across Louisiana on 10 November 2017 caught the attention of several people on Twitter — GOES-16 “Red” Visible (0.64 µm) images (above) showed the motion of this cloud during the 1317-2052 UTC period.

In a 3-panel comparison of GOES-16 “Red” Visible (0.64 µm), Near-Infrared “Cirrus” (1.37 µm) and “Clean” Infrared Window (10.3 µm) images (below), the strong signature (bright white) on the 1.37 µm imagery indicated that this feature was a cirrus cloud. The uncharacteristically-warm Infrared brightness temperatures exhibited by this feature were due to the fact that the thin cirrus allowed warmer thermal radiation from the surface to pass through the cloud and reach the satellite detectors.

GOES-16 Visible (0.64 µm, top), Near-Infrared

GOES-16 Visible (0.64 µm, top), Near-Infrared “Cirrus” (1.37 µm, middle) and “Clean” Infrared Window (10.3 µm, bottom) images [click to play MP4 animation]

Rawinsonde profiles from Lake Charles and Slidell, Louisiana at 12 UTC (below) showed the presence of a moist layer aloft (at an altitude around 9.5 km or 31,100 feet) — the cirrus cloud feature likely resided within this moist layer, which would explain why the cloud was slow to dissipate. Air temperatures within this moist layer were in the -40 to -50ºC range, and winds were from the west-northwest at speeds of 30-35 knots (which was consistent with the cloud motion seen on satellite imagery).

Rawinsonde data for Lake Charles and Slidell, Louisiana at 12 UTC on 10 November [click to enlarge]

Rawinsonde data for Lake Charles and Slidell, Louisiana at 12 UTC on 10 November [click to enlarge]

Even with the higher spatial resolution Infrared Window imagery (1 km, vs 2 km at the satellite sub-point for GOES-16) of Terra MODIS (below), the minimum Infrared brightness temperature of the cirrus cloud feature was still a relatively warm -31ºC.

Terra MODIS Visible (0.65 µm), Cirrus (1.375 µm) and Infrared Window (11.0 µm) images [click to enlarge]

Terra MODIS Visible (0.65 µm), Cirrus (1.375 µm) and Infrared Window (11.0 µm) images [click to enlarge]

Another interesting aspect of this small cirrus cloud is that it was casting a shadow to the north (due to the low November sun angle) — and the Terra MODIS Land Surface Temperature product (below) indicated that LST values were about 10 degrees F cooler within the shadow (low to middle 60s F) compared to adjacent sunlit ground (low to middle 70s F). That particular area was not normally cooler in terms of LST values (because of varying vegetation, soil type, a deep lake, etc.), since it did not show up as a cooler feature on the following day.

Terra MODIS Visible (0.65 µm) image and Land Surface Temperature product [click to enlarge]

Terra MODIS Visible (0.65 µm) image and Land Surface Temperature product [click to enlarge]

Additional images and ground-based photos of the cirrus cloud feature can be found on this AccuWeather blog.