Boundary layer wave clouds over Kansas

May 2nd, 2020 |

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with plots of pilot reports of turbulence and AIRMET boundaries [click to play animation | MP4]

GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed widespread boundary layer wave clouds across much of Kansas and far eastern Colorado on 02 May 2020. Although there was a temporary outage of pilot report data from 18-19 UTC, there was one pilot report of light turbulence over Hays, Kansas (KHYS) at an altitude of 6500 feet at 2041 UTC. An AIRMET for the potential of turbulence below 7000 feet had been issued at 14 UTC. There was a hint of some wave interference, which may have enhanced turbulence potential.

There was also a subtle signature of these waves seen in GOES-16 Low-level Water Vapor (7.3 µm) images (below).

GOES-16 Low-level Water Vapor (7.3 µm) images, with plots of pilot reports of turbulence and AIRMETs boundaries [click to play animation | MP4]

GOES-16 Low-level Water Vapor (7.3 µm) images, with plots of pilot reports of turbulence and AIRMETs boundaries [click to play animation | MP4]

Transverse banding over California

February 4th, 2020 |

GOES-17

GOES-17 “Red” Visible (0.64 µm) and Near-Infrared “Cirrus” (1.37 µm) images, with pilot reports of turbulence [click to play animation | MP4]

1-minute Mesoscale Domain Sector GOES-17 (GOES-West) “Red” Visible (0.64 µm) and Near-Infrared “Cirrus” (1.37 µm) images (above) displayed widespread “transverse banding” — elongated cirrus elements oriented perpendicular to the ambient jet stream flow — that was migrating southward across California on 04 February 2020. This satellite signature is an indicator of potential turbulence, which in this case did indeed result in several pilot reports of light to moderate turbulence.

One of the pilot reports over Salinas, California at 2150 UTC (below) indicated Clear Air Turbulence (CAT) at an altitude of 30,000 feet — this suggests that the aircraft might have been flying just above or below the actual cirrus bands.

GOES-17 "Red" Visible (0.64 µm) image with a pilot report of Clear Air Turbulence at 2150 UTC [click to enlarge]

GOES-17 “Red” Visible (0.64 µm) image with a pilot report of Clear Air Turbulence at 2150 UTC [click to enlarge]

Severe turbulence over Arizona and New Mexico

February 3rd, 2020 |

GOES-16 Mid-level Water Vapor (6.9 µm) images, with pilot reports of turbulence [click to play animation | MP4]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with pilot reports of turbulence [click to play animation | MP4]

GOES-16 (GOES-East) Mid-level Water Vapor (6.9 µm) images (above) showed numerous orographic waves over eastern Arizona and western New Mexico on 03 February 2020. There were several high-altitude pilot reports of turbulence across that region, including severe turbulence associated with mountain waves at 43,000 feet and at 39,000 feet (below). The turbulence encounter at 39,000 feet noted an aircraft speed fluctuation of +/- 20 knots, along with a drop in altitude of 1600 feet.

GOES-16 Mid-level Water Vapor (6.9 µm) image, with pilot report of severe turbulence at 43,000 feet [click to enlarge]

GOES-16 Mid-level Water Vapor (6.9 µm) image, with pilot report of severe turbulence at 43,000 feet [click to enlarge]

GOES-16 Mid-level Water Vapor (6.9 µm) image, with pilot report of severe turbulence at 39,000 feet [click to enlarge]

GOES-16 Mid-level Water Vapor (6.9 µm) image, with pilot report of severe turbulence at 39,000 feet [click to enlarge]

 

Interesting circular contrail over South Dakota

January 29th, 2020 |

Multi-panel images of all 16 ABI spectral bands from GOES-16 [click to play animation | MP4]

Multi-panel images of all 16 ABI spectral bands from GOES-16 [click to play animation | MP4]

Multi-panel images of all 16 ABI spectral bands from GOES-16 (GOES-East) (above) revealed an interesting circular contrail over northeastern South Dakota on 29 January 2020. A signature of this contrail was evident in all 16 bands — visible, near-infrared and infrared. This feature was likely formed by a military aircraft performing training exercises over the area.

A sequence of GOES-16 ABI spectral band images covering that same 1751-2001 UTC time period (below) provided a larger view of the circular contrail — whose diameter was about 10-12 miles — along with a linear contrail located about 30 miles to the southwest.

Sequence of GOES-16 ABI spectral band images [click to play animation | MP4]

Sequence of GOES-16 ABI spectral band images [click to play animation | MP4]

A toggle between GOES-16 “Red” Visible (0.64 µm) and Near-Infrared “Cirrus” (1.37 µm) images at 1911 UTC (below) showed that the darker signature seen in the Visible imagery was a shadow cast by the higher-altitude contrail onto the top of the low-altitude stratus clouds. A similar northwestward shadow offset (of about 5 miles) was apparent with the linear contrail feature.

GOES-16

GOES-16 “Red” Visible (0.64 µm) and Near-Infrared “Cirrus” (1.37 µm) images at 1911 UTC [click to enlarge]

The southwestward shift of the higher-altitude contrail (with respect to the surface shadow) was not due to parallax — this webapp shows that the direction of parallax shift over that region would be northwestward for cloud features at altitudes of 15,000 feet and 30,000 feet (below).

Parallax correct vectors (green arrows) and magnitudes (red. in km) for cloud features at 15,000 feet and 30,000 feet over the CONUS domain [click to enlarge]

Parallax correct vectors (green arrows) and magnitudes (red. in km) for cloud features at 15,000 feet and 30,000 feet over the CONUS domain [click to enlarge]

Plots of rawinsonde data from Aberdeen, South Dakota (below) showed an increase in moisture during the day within the 500-300 hPa layer — due to its relatively slow southeastward propagation, the circular contrail likely existed within the lower portion of that layer (where wind speeds were less).

Plots of rawinsonde data from Aberdeen, South Dakota [click to enlarge]

Plots of rawinsonde data from Aberdeen, South Dakota [click to enlarge]

A signature of the circular contrail was seen in all 3 of the GOES-16 Water Vapor spectral bands — weighting functions derived using rawinsonde data from Aberdeen, South Dakota (below) showed either primary or secondary peaks within the 500-300 hPa layer.

GOES-16 Water Vapor weighting functions derived using rawinsonde data from Aberdeen, South Dakota [click to enlarge]

GOES-16 Water Vapor weighting functions derived using rawinsonde data from Aberdeen, South Dakota [click to enlarge]

Thanks go out to Jay Trobec (@trobec), KELOLAND TV in Sioux Falls, for alerting us about this interesting example.