The GOES-16 (GOES-East) Total Precipitable Water product (above) showed a northerly/northwesterly flow of tropical moisture toward New England during the day on 24 July 2018, with TPW values in the 1.0 to 1.6 inch range moving toward the region. As this moist air moved over relatively cool water — as indicated by Aqua MODIS Sea Surface Temperature values generally in the 60s F on the previous day (below) — areas of marine boundary layer fog/stratus developed.

1-minue Mesoscale Domain Sector GOES-16 “Red” Visible (0.64 µm) images (below) revealed interesting patterns in the resulting marine layer fog/stratus — for example, bow shock waves along the eastern edges of Nantucket Island and Cape Cod, and narrow clear swaths to the lee of some of the smaller islands off the coast of Maine.

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Suomi NPP VIIRS Shortwave Infrared (3.75 µm), Near-Infrared (1.61 and 2.25 µm) and Day/Night Band (0.7 µm) images (above) showed thermal signatures and the bright glow of wildfires in the Athens, Greece area at 0005 UTC or 3:05 am local time on 24 July 2018. The 2 largest fires were burning in the vicinity of Kineta and Mati.

Similar images from an overpass of the NOAA-20 satellite 50 minutes later are shown below.

Over 70 deaths have resulted from these fast-moving wildfires, which were driven by strong winds (below).

VIIRS images courtesy of William Straka, CIMSS.

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GOES-16 “Clean” Infrared Window (10.3 µm) images (above) revealed a well-defined “warm trench” signature (ring of brighter red enhancement) surrounding the cold overshooting top (cluster of pixels enhanced as black to lighter shades of gray) of a thunderstorm in far eastern Colorado during the nighttime hours on 22 July 2018. This warm trench appears to be a ring of compensating subsidence immediately surrounding the vigorous overshooting top; the cold/warm (overshooting_top/warm_trench) “delta-T” on the 0412 UTC image was 16.4ºC (-85.5ºC / -67.1ºC). Just to the south, at 0453 UTC there was a northerly peak wind gust to 45 knots or 52 mph at KITR (Burlington Colorado: plot | text) as the updraft supporting the overshooting top collapsed — but no other SPC storm reports were seen in that area.

A 250-meter resolution Terra MODIS Infrared Window (11.0 µm) imageat 0402 UTC (below) with a slightly different color enhancement showed similar delta-T values (-81ºC/-67ºC) with the overshooting top / warm trench. The diameter of the warm trench was approximately 30-40 miles.

A plot of 00 UTC rawinsonde data from North Platte, Nebraska (below) showed a tropopause temperature of -73ºC at an altitude of 15.7 km or 51,500 feet — so the much colder infrared brightness temperatures seen on GOES and MODIS imagery were indicative of a very robust overshooting top that penetrated the tropopause a significant distance.

The GOES-16 Cloud Top Height product at 0412 UTC (below) indicated values of 54,000 ft / 49,000 ft for the cold overshooting top / warm trench features — however, note that the resolution of this infrared-derived product is 10 km (and the accuracy is within 1500 feet).

Another interesting (and yet-to-be-explained) feature was an arc of warming cloud-top infrared brightness temperatures that was seen propagating southwestward toward the overshooting top / warm trench signature. A larger-scale view (below) showed this wave feature moving from southwestern Nebraska at around 02 UTC to southern Colorado/Kansas by 10 UTC.

This cloud-top wave feature was also apparent on GOES-16 Upper-level Water Vapor (6.2 µm) images (below) — at times the wave was tracked by Derived Motion Winds at speeds of 20-30 knots (0252 UTC | 0337 UTC | 0922 UTC). According to rawinsonde data from Dodge City, Kansas (plot | data) as well as North Platte, winds with a northerly to easterly component were only found at altitudes of 20 km or higher!

Special thanks to NWS Grand Rapids forecasters Brett Borchardt and TJ Turnage for bringing this case to our attention!

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Landsat-8 False Color Red-Green-Blue (RGB) images viewed using RealEarth (above) is zoomed in (final image) to show a large iceberg (snow and ice appear as cyan) near the island community of Innaarsuit, Greenland (shades of light green) on 20 July 2018. Media stories about this iceberg can be found here and here.

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