A sequence of VIIRS True Color Red-Green-Blue (RGB) images from NOAA-20 and Suomi NPP viewed using RealEarth (above) showed the volcanic ash plume from an eruption of Mount Etna in Italy on 24 December 2018.

A toggle between NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images (below) revealed a colder cloud plume at higher altitude along the southern edge of the tan/brown volcanic ash plume. A thermal anomaly or “hot spot” (dark black pixels) could be seen at the snow-covered volcano summit.

The volcanic plume could be quantitatively analyzed using Suomi NPP VIIRS Ash Probability, Ash Height, Ash Loading and Ash Effective Radius products from the NOAA/CIMSS Volcanic Cloud Monitoring site at 1154 UTC (below).

Since the bulk of the volcanic plume was high in ash content with minimal water or ice cloud, a good signature was seen using Meteosat-11 Split Window (11-12 µm) Brightness Temperature Difference images (below).

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Himawari-8 “Clean” Infrared Window (10.4 µm) images (above) showed the volcanic cloud from an eruption of Anak Krakatau in Indonesia on 22 December 2018. Two distinct pulses were evident: the first began around 1340 UTC, with the second starting around 1520 UTC. At times the cloud-top infrared brightness temperatures were -80ºC or colder (violet enhancement) — which roughly corresponded to altitudes around 15-16 km on rawinsonde data from nearby Jakarta (WIII) (below). The eruption process appears to have played a role in generating a tsunami that was responsible for over 400 fatalities — via a partial collapse of the southern flank of the volcano which then triggered an undersea landslide (visualization).

After sunrise, the volcanic cloud was evident in Himawari-8 “Red” Visible (0.64 µm) images (below) — a toggle between Visible and Infrared images at 0110 UTC showed an example of one of the cold overshooting tops.

At the onset of the eruption, multi-spectral retrievals from the NOAA/CIMSS Volcanic Cloud Monitoring site showed Ash Height values of 12-14 km and Ash Loading values of 9-10 g/m2 (below). However, after about 1.5 hours the extremely high water and ice content of the volcanic cloud prevented further retrievals of such parameters.

A toggle between NOAA-20 VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images viewed using RealEarth (below) showed the volcanic cloud at 0610 UTC on 23 December.

A comparison of Infrared Window images from NOAA-20 VIIRS (11.45 µm) and Himawari-8 AHI (10.4 µm) at 0610 UTC (below) demonstrated the advantage of improved spatial resolution — the minimum cloud-top infrared brightness temperature of the overshooting top feature was significantly colder on the 375-m resolution VIIRS image (-87ºC, darker shade of violet) than on the corresponding AHI image with 2-km resolution at satellite sub-point (-74.2ºC).

There was also a significant amount of lightning associated with this volcanic cloud:

#Krakatoa/#Krakatau #lightning update: Rough counts have had peak values of 90 lightning events per minute detected around the volcano! Between ~1430 UTC 22 Dec and ~1900 UTC 23 Dec, there have been tens of thousands of lightning events detected by GLD360. pic.twitter.com/iekphVjsD2

— Chris Vagasky (@COweatherman) December 23, 2018

Here’s the @WWLLN lightning strike detection map for #Krakatau on Dec 23: 10856 strokes. Remarkable. pic.twitter.com/6xxdYSgjmu

— Simon Carn (@simoncarn) December 24, 2018

A comparison of Himawari-8 Visible and Infrared images showed the persistent volcanic cloud following sunrise on 23 December (below). The pulsing overshooting tops continued to exhibit infrared brightness temperatures as cold as -80ºC at times.

===== 24 December Update =====

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images (above) provided a detailed view of the volcanic cloud at 0550 UTC on 24 December.

A long animation of Himawari-8 “Clean” Infrared Window (10.4 µm) images spanning over 48 hours from the onset of the eruption (below) showed the remarkably persistent volcanic cloud, with pulsing overshooting tops anchored over Anak Krakatau.

===== 25 December Update =====

In a toggle between NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 0710 UTC on 25 December (above), a few -90ºC pixels could be seen embedded within the darker purple area of the overshooting top on the Infrared image. Note that there was some westward parallax shift of the image features, due to the scene being near the edge of the VIIRS scan.

The coldest pixels on another NOAA-20 VIIRS Infrared image at 1810 UTC (below) were still within the -80 to -87ºC range.

An updated long animation of Himawari-8 Infrared images (below) continued to show periodic bursts of cold pixels within overshooting tops above the eruption site.

===== 28 December Update =====

An updated long animation of Himawari-8 Infrared images (above) revealed that the volcanic thunderstorm — which had persisted over the eruption site nearly continuously since 1350 UTC on 22 December — underwent its final pulse around 0640 UTC on 28 December, and was no longer seen after 0900 UTC. The volcanic thunderstorm began its transition from being nearly continuous to a phase of discrete discontinuous pulses after about 0500 UTC on 27 December; the last image with cloud-top infrared brightness temperatures of -80ºC or colder was 2110 UTC on that day.

NOAA-20 captured one of the final convective pulses around 0620 UTC on 28 December (below), when the coldest cloud tops were in the -50 to -55ºC range (yellow to orange enhancement).

Here it is…a loop of #lightning from 2:30am MT 22 Dec until 2:30am MT 28 December from #Krakatau/#Krakatoa detected by GLD360. A truly incredible event. pic.twitter.com/nvStqoMaAC

— Chris Vagasky (@COweatherman) December 28, 2018

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A meteor entered the Earth’s atmosphere over the Bering Sea (east of Kamchatka) on 18 December 2018. Himawari-8 “Red” Visible (0.64 µm) images (above) showed a bright streak at 23:50 UTC — and a dark-colored debris trail was also evident northwest of this bright streak, which subsequently drifted northeastward. Signatures of the meteor were also captured with the Terra satellite.

A warm thermal anomaly was apparent (at the southern end of the bright streak) on the 2350 UTC Himawari-8 Shortwave Infrared (3.9 µm) image (below).

GOES-17 was only scanning the Full Disk at 15-minute intervals, so the initial bright meteor streak that was seen with Himawari-8  was not not captured; however, the dark meteor debris cloud drifting northeastward could be followed on Visible imagery (below).

* GOES-17 images shown here are preliminary and non-operational *

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Preliminary Damage Results for Port Orchard Tornado have been released. Survey finds EF-2 #tornado damage from Tuesday December 18th. Details in graphic and at: https://t.co/fnaZxgYG6U #wawx #PortOrchardTornado pic.twitter.com/jxpsBgkmgC

— NWS Seattle (@NWSSeattle) December 19, 2018

* GOES-17 images shown here are preliminary and non-operational *

A rare December tornado occurred in Port Orchard, Washington on 18 December 2018. GOES-17 “Red” Visible (0.64 µm) images (above) and “Clean” Infrared Window (10.3 µm) images (below) showed the thunderstorms that moved eastward across the area in the wake of the passage of an occluded front earlier in the day.

Due to the relatively large GOES-17 satellite viewing angle (or zenith angle) of 56.38 degrees, there was a modest amount of parallax error in terms of the actual location of cloud-top features associated with the tornado-producing storm. A toggle between GOES-17 Visible and Infrared images at 2147 UTC with SPC tornado reports plotted at their actual and “parallax-corrected” locations (assuming a mean storm-top height of 8 km) are shown below — note how the parallax-corrected tornado plot location more closely aligns with top the parent thunderstorm.

A comparison of VIIRS Infrared Window (11.45 µm) images from Suomi NPP (Washington overpass time: 2042 UTC) and NOAA-20 (Washington overpass time: 2132 UTC) is shown below. The coldest cloud-top infrared brightness temperatures on the VIIRS images were -42ºC (bright green enhancement), which corresponded to altitudes of 7-8 km on 00 UTC rawinsonde data from Quillayute, Washington (plot).

A toggle between NOAA-20 VIIRS Infrared Window (11.45 µm) images at the local overpass times of 1952 UTC and 2132 UTC, viewed using RealEarth (below), provided a closer view of the convection.

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