NASA Worldview imagery of Terra (launched in 1999 and still producing imagery!) MODIS true-color imagery, above, from this link, shows an ellipsoidal feature to the southeast of Guam with cloud development along its southern flank. Terra was passing west of Guam at about 0045 UTC on 20 May 2023, with the rising sun in the eastern sky (Terra orbits for that day over the western Pacific are here, taken from this site). Sunglint in visible imagery is caused by reflection of solar energy off the ocean’s surface; the concentration — brightness — of the sunglint is related to the ocean state. If the ocean surface is completely flat, reflection would be in one region that would be very bright, and the surrounding ocean where winds are light would be dark. Beyond the region of light winds, the sea would appear bright. Thus, changes in the sunglint apparent above are likely related to changes in the windspeed over the ocean in the region.

Cloud debris exists near the center of this ellipse, and it’s reasonable to assume this is a dying convective feature, and that the ellipse outlines the outward-propagating downdraft. The animation of Himawari Clean Window infrared (Band 13, 10.4 µm) and visible imagery (Band 3, 0.64 µm), below, from 0010 to 0100 UTC on 20 May, shows motion cloud features consistent with that theory.

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1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) showed Tropical Depression Two as it developed over the northern Gulf of Mexico on 01 June 2023. The low-level circulation center became exposed late in the day, as deep convection remained focused to the northeast of the disturbance center — cloud-top infrared brightness temperatures of the thunderstorm overshooting top pulses were as cold as -65ºC at 2322 UTC (below).

Although TD Two was forecast to move southward across warmer water associated with the Gulf of Mexico Loop Current (Sea Surface Temperature | Ocean Heat Content), modest amounts of deep-layer wind shear from the CIMSS Tropical Cyclones site (below) did not favor a large amount of intensification.

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1-minute Mesoscale Domain Sector GOES-18 (GOES-West) “Clean” Infrared Window (10.3 µm) images (above) are shown with and without an overlay of GLM Flash Extent Density and contours of Lightning Cast Probability from 1530-1915 UTC on 01 June 2023 — the time period covering outdoor graduation ceremonies at the Air Force Academy in eastern Colorado. LightningCast provided good lead time, with Probability values over the Air Force Academy first reaching 75% at 1619 UTC — the first pixel of Flash Extent Density (FED) over the Academy location was at 1815 UTC (with FED becoming more frequent and widespread over that area after 1851 UTC).

Air Force Academy Graduation

Thunderbirds and lightning!

Thanks to Vicki Rusinak Caldwell for sending this to me! #COwx #Lightning #AFA pic.twitter.com/QjPLyAvw1b

— Kody Wilson (@kodythewxguy) June 1, 2023

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GOES-16 (GOES-East) Shortwave Infrared (3.9 µm) and Fire Power derived product images during the 5-day period from 27 May – 31 May 2023 (above) showed the thermal signature of wildfires burning in far southern Nova Scotia — which forced the evacuation of 40% of the residents in the area southwest of Shelburne (near airport identifier CWOS). 3.9 µm infrared brightness temperatures occasionally reached 135ºC (not far below the 137.71ºC saturation temperature of the GOES-16 ABI Band 7 detectors), with Fire Power values exceeding 2700 MW at times (the Fire Power derived product is a component of the Fire Detection and Characterization Algorithm). On 28 May, strong westerly winds within the warm sector of a midlatitude cyclone caused a rapid eastward expansion of the fire’s thermal signature.

A sequence of GOES-16 True Color RGB and Nighttime Microphysics RGB images during 27-31 May from the CSPP GeoSphere site (below) showed the varying daytime smoke transport along with the fire’s nocturnal thermal anomaly (darker shades of purple) during that same 5-day period.

In a toggle between NOAA-20 VIIRS True Color RGB and False Color RGB images valid at 1700 UTC on 31 May (below), individual smoke plume point sources could be seen in the True Color RGB image, while the fire burn scar (darker shades of brown) and active fires (brighter shades of pink) were evident in the False Color RGB image. VIIRS data used to create these images were downloaded and processed via the CIMSS/SSEC Direct Broadcast ground station.

During the preceding nighttime hours, a toggle between Suomi-NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.74 µm) images (below) showed the nocturnal glow and thermal signature of the fires at 0626 UTC on 31 May.

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