High cloud shadow over eastern Iowa

June 18th, 2018 |

It’s always good to get a question that lends itself well to the “What the heck is this?” blog category. The answer, as is often the case, relies on an examination of imagery from a variety of GOES-16 ABI bands.  To begin, note the darker feature seen on 1-minute Mesoscale Domain Sector GOES-16 “Blue” Visible (0.47 µm), “Red” Visible (0.64 µm) and Near-Infrared “Vegetation” (0.86 µm) images (below), which was moving northeastward across eastern Iowa and passing just to the west of Waterloo (KALO) on the morning of 18 June 2018.

GOES-16 "Blue" Visible (0.47 µm), "Red" Visible (0.64 µm) and Near-Infrared "Snow/Ice" (1.61 µm) images

GOES-16 “Blue” Visible (0.47 µm, left), “Red” Visible (0.64 µm, center) and Near-Infrared “Vegetation” (0.86 µm, right) images [click to play animation | MP4]

To explore the initial hypothesis that this might be a shadow from a higher-altitude cloud feature, GOES-16 Near-Infrared “Cirrus” (1.37 µm), Mid-level Water Vapor (6.9 µm) and Upper-level Water Vapor (6.2 µm) images were examined (below), which did indeed reveal a small cloud element aloft that was drifting in the same direction as the darker feature seen above.

GOES-16 Near-Infrared

GOES-16 Near-Infrared “Cirrus” (1.37 µm, left), Mid-level Water Vapor (6.9 µm, center) and Upper-level Water Vapor (6.2 µm, right) images [click to play animation | MP4]

Finally, a comparison of GOES-16 Near-Infrared “Cirrus” (1.37 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.3 µm) images (below) showed that this small (and likely thin) high-altitude cloud exhibited no signature in the Shortwave Infrared, but did exhibit a 10.3 µm brightness temperature as cold as -20ºC (cyan enhancement) at times.

GOES-16 Near-Infrared

GOES-16 Near-Infrared “Cirrus” (1.37 µm, left), Shortwave Infrared (3.9 µm, center) and “Clean” Infrared Window (10.3 µm, right) images [click to play animation | MP4]

12 UTC rawinsonde data from Davenport, Iowa (below) showed southwesterly winds and an air temperature just below -20ºC at an altitude of around 9.6 km.

12 UTC rawinsonde data from Davenport, Iowa [click to enlarge]

12 UTC rawinsonde data from Davenport, Iowa [click to enlarge]

Thanks to Andrew Ansorge (NWS DMX) and Rich Mamrosh (NWS GRB) for alerting us to this interesting feature!

Lava flows continue from Kilauea’s Lower East Rift Zone

June 18th, 2018 |

NOAA-20 VIIRS Day/Night Band (0.7 µm), Shortwave Infrared I04 (3.75 µm), Shortwave Infrared M13 (4.05 µm) and Longwave Infrared (11.45 µm) images [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm), Shortwave Infrared I04 (3.75 µm), Shortwave Infrared M13 (4.05 µm) and Longwave Infrared (11.45 µm) images [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm), Shortwave Infrared I04 (3.75 µm), Shortwave Infrared M13 (4.05 µm) and Longwave Infrared (11.45 µm) images (above) showed signatures of the ongoing lava flows from the Lower East Rift Zone of the Kilauea volcano on the Big Island of Hawai’i at 1225 UTC (2:25 am local time) on 18 June 2018.

Note how the central ribbon of hottest lava flow (which continues its active ocean entry) saturated the I04 3.75 µm image, causing a “wrap-around” effect to display cold brightness temperatures (white pixels) — although the M13 4.05 µm band has a lower spatial resolution, it saturates at much higher temperatures, and sensed brightness temperatures in the 480 to 557 K range. The Infrared images also showed evidence of steam clouds flowing southward over the adjacent offshore waters.

A webcam image from near Kapoho (PGcam) around the time of the NOAA-20 VIIRS images is shown below. The active Fissure 8 is near the center of the image.

Webcam image from near Kapoho [click to enlarge]

Webcam image from near Kapoho [click to enlarge]

VIIRS imagery and webcam capture courtesy of William Straka (CIMSS).

Severe weather in southern Wisconsin

June 16th, 2018 |

GOES-16

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 and surface station identifiers plotted in yellow [click to play MP4 animation]

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) showed the development of thunderstorms over southern Wisconsin during the afternoon and evening hours on 16 June 2018. There were reports of hail, damaging winds and 1 brief tornado (SPC storm reports | NWS MKX summary). The pulsing of short-lived overshooting tops is evident in both Visible and Infrared imagery; above-anvil cloud plumes can also be seen in Visible imagery, drifting southeastward from the more robust overshooting tops. Note at 2000 UTC the boundary that was oriented approximately north-to-south, with widespread cumulus clouds to the west and generally cloud-free conditions to the east: this was a lake breeze boundary that had migrated inland from Lake Michigan. Many of the storms appeared to intensify as they interacted with this boundary.

Severe thunderstorms in North Dakota

June 14th, 2018 |

GOES-16 Mid-level Water Vapor (6.9 µm) images, with SPC storm reports plotted in red [click to play MP4 animation]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with SPC storm reports plotted in red [click to play MP4 animation]

GOES-16 (GOES-East) Mid-level Water Vapor (6.9 µm) images (above) revealed the circulation of a shortwave aloft (500 hPa analyses) that was moving from the northern Rockies to the southern Canadian Prairie Provinces on 14 June 2018. The approach of this shortwave was helping to enhance large-scale forcing for ascent, as an occluded surface low developed over western North Dakota (surface analyses) — at 1630 UTC, SPC issued a Moderate Risk for severe thunderstorms across far northern North Dakota.

A Mesoscale Domain Sector was positioned over that region, providing images at 1-minute intervals; a comparison of “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (below) showed the development of this severe convection, which produced hail as large as 3.0 inches in diameter and 4 tornadoes (NWS Bismarck | NWS Grand Forks). The images include plots of SPC storm reports — just across the US/Canada border, storm reports in southern Saskatchewan/Manitoba can be seen here. Some of these storms exhibited very high radar reflectivity values, as shown here and here.

GOES-16

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

A larger-scale view of 1-minute GOES-16 Visible images (below) showed well-defined parallel inflow feeder bands moving into the southern flank of the storm approaching Minot (KMOT) and Minot Air Force Base (KMIB) during the 1600-1900 UTC time period. Distinct above-anvil plumes were seen with a number of the stronger storms.

1-minute GOES-16

1-minute GOES-16 “Red” Visible (0.64 µm) images, with SPC storm reports plotted in red [click to play MP4 animation]

The corresponding larger-scale view of 1-minute GOES-16 Infrared images (below) extended past sunset, and showed the final tornado that began around 0324 UTC.

1-minute GOES-16

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