On 23 April 2019, a Ground Systems update resulted in a change to the ‘brightness’ (in the form of dimming) of the GOES-16 Band 2 (0.64 µm) visible imagery (as noted in this calibration events log).  The  calibration coefficients used for this band were determined in the lab before the launch. (Other calibration information is collected on-orbit.) GOES-R Advanced Baseline Imager (ABI) visible imagery have been compared to visible imagery from polar-orbiting satellites in the past several years (see this page), and GOES-R ABI Band 2 (0.64 µm) radiances were consistently larger than measurements from Suomi NPP and NOAA-20 using the Visible-Infrared Imaging Radiometer Suite (VIIRS).

ABI calibration coefficients for GOES-16 were modified on 23 April, using plausible values from pre-launch lab measurements. Thus, Band 2 radiances decreased by about 6.9%. This will have an impact on the computed albedo as shown above: the later date (after the calibation change) is slightly darker than the earlier (before the calibration change). This change means that Band 2 radiances and albedo are more closely aligned with values from other satellites. A similar toggle over Texas is shown below.

Note: A similar change for GOES-17 was implemented at 1540 UTC on 27 April 2019.

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On 30 April, JMA Himawari-8 “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.4 µm) images (above) showed the formation of the first known pyrocumulonimbus (pyroCb) cloud of the 2019 Northern Hemisphere wildfire season. The pyroCb developed within the warm sector of an approaching midlatitude cyclone (surface analyses) in the Russian Far East, between still-ice-covered Lake Bolon and the Amur River. The cloud-top infrared brightness temperature first reached the -40ºC “pyroCb threshold” at 0310 UTC; note that the pyroCb cloud top appears warmer (darker shades of gray) than those of surrounding thunderstorms in the Shortwave Infrared images — a characteristic of enhanced solar reflection off the smaller ice crystals that are found in pyroCb cirrus anvils.

A faster animation revealed the rapid northeastward run of the large pyroCb-producing fire on Shortwave Infrared imagery.

In a sequence of three VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP as viewed using RealEarth (above), the coldest cloud-top infrared brightness temperature of the pyroCb was -59ºC — which closely corresponded to the tropopause temperature on 00 UTC rawinsonde data from Habarovsk (below), located just southwest of the fire region.

Here’s the aerosol index from N20 OMPS pic.twitter.com/x3T12mi5ml

— Colin Seftor (@colin_seftor) April 30, 2019

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A sequence of VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images from Suomi NPP and NOAA-20 as viewed using RealEarth (above) showed “Storm Hannah” as it approached Ireland and the United Kingdom on 26 April 2019. The midlatitude cyclone had peaked in intensity as a Hurricane Force low around that time (surface analyses).

EUMETSAT Meteosat-11 Water Vapor (6.25 µm) images (below) showed winds gusting to 40-65 knots at several sites in southern Ireland and southern England, as the dry slot air stream moved across the region. In Ireland the peak wind gust was 66 knots at Mace Head, with 64 knots at Shannon — wind gusts in southern England included 71 knots at Aberderon, 68 knots at Pembrey Sands and 52 knots at Valley.

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EUMETSAT Meteosat-8 Visible (0.8 µm) images (above) and Infrared Window (10.8 µm) images (below) showed Category 4 Cyclone Kenneth (12 UTC JTWC advisory) making landfall along the northeast coast of Mozambique (north of Pemba FQPB: surface observations) on 25 April 2019. Kenneth had been moving over warm water and through an environment of low deep-layer wind shear, factors favorable for its rapid intensification (ADT | SATCON). After making landfall, Kenneth rapidly weakened to Category 1 intensity by 18 UTC — but Metop-A ASCAT winds of 40-49 knots were still sampled along the coast on the rear periphery of the storm. The slow inland movement of the remnants of Kenneth combined with copious amounts of tropical moisture as depicted by MIMIC TPW posed a concern for potential flooding problems.

VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images from Suomi NPP and NOAA-20, viewed using RealEarth (below), provided higher-resolution views of Kenneth a few hours prior to landfall. This was the strongest tropical cyclone landfall on record for the northern portion of Mozambique, as discussed here.

GCOM-W1 AMSR2 Microwave (89 GHz) image (below, courtesy of William Straka, CIMSS) showed the eye and spiral band structures near the Mozambique coast at 1030 UTC on 25 April. The evolution of the eye since its initial formation on 23 April was evident in the MIMIC TC product.

A longer animation of Meteosat-8 Infrared images (below) during the later half of its storm track showed the formation of an eye as Kenneth began its period of rapid intensification on 24 April. Cloud-top infrared brightness temperatures were -90ºC and colder (yellow pixels embedded with darker shades of purple) during the 1030-1800 UTC period on 24 April. Note that the center of Kenneth passed just north of the island of Grande Comore soon after the eye had developed — at Prince Said Ibrahim International Airport FMCH in Moroni, southeast winds gusted to 65 knots at 21 UTC 0n 24 April as the southern eyewall passed over the island.

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images (below, courtesy of William Straka, CIMSS) showed Kenneth at 2232 UTC on 24 April, shortly before the tropical cyclone had reached Category 4 intensity. Ample illumination from the Moon — in the Waning Gibbous phase, at 73% of Full — provided an excellent example of the “visible image at night” capability of the VIIRS Day/Night Band.

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