Hurricane-Force low over the Aleutian Islands

December 29th, 2018 |
Water Vapor images from GOES-17 (6.9 µm, left) and GOES-15 (6.5 µm, right) [click to play animation | MP4]

Water Vapor images from GOES-17 (6.9 µm, left) and GOES-15 (6.5 µm, right) [click to play animation | MP4]

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

A mid-latitude cyclone moved northward over the far western Aleutian Islands late in the day on 28 December 2018, intensifying to a Hurricane Force low pressure system by 06 UTC on 29 December (surface analyses). A comparison of GOES-17 and GOES-15 (GOES-West) Water Vapor images (above) highlighted the improved spatial resolution of the GOES-17 data (2 km at satellite sub-point, vs 4 km for GOES-15). The view from GOES-15 was more oblique, since it was positioned at 128º W longitude (compared to 137.2º W longitude for GOES-17). GOES-17 is scheduled to become the operational GOES-West satellite in January 2019.

A toggle between GOES-17 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images at 1100 UTC is shown below. Although the satellite viewing angle was large, good detail could still be seen.

GOES-17 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images at 1100 UTC [click to enlarge]

GOES-17 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images at 1100 UTC [click to enlarge]

A sequence of Suomi NPP VIIRS Visible (0.64 µm), Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images (below) showed the storm as it was intensifying — the peak surface wind gust at Shemya Eareckson Air Station (PASY) was 66 knots at 1024 UTC. Since the Moon was in the Waning Gibbous phase (at 60% of Full), there was ample illumination to provide a useful “visible image at night” with the VIIRS Day/Night Band at 1403 UTC (4:03 AM local time).

Suomi NPP VIIRS Visible (0.64 µm), Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm), Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

A time series plot of hourly surface weather data from Shemya during the time period of the GOES-17/15 Water Vapor image comparison is shown below, along with a more detailed time series that included Special Reports in addition to the standard Hourly Reports..

Time series plot of surface weather data from Shemya Eareckson Air Station [click to enlarge]

Time series plot of Hourly surface weather data from Shemya Eareckson Air Station [click to enlarge]

Time series plot of Hourly and Special surface weather data from Shemya Eareckson Air Station [click to enlarge]

Time series plot of Hourly and Special surface weather data from Shemya Eareckson Air Station [click to enlarge]

Eruption of Mount Etna in Italy

December 24th, 2018 |

VIIRS True Color RGB images from NOAA-20 (at 1110 and 1220 UTC) and Suomi NPP (at 1200 UTC) [click to enlarge]

VIIRS True Color RGB images from NOAA-20 (at 1110 and 1220 UTC) and Suomi NPP (at 1154 UTC) [click to enlarge]

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.

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 1250 UTC [click to enlarge]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 1250 UTC [click to enlarge]

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).

Suomi NPP VIIRS Ash Probability, Ash Height, Ash Loading and Ash Effective Radius at 1154 UTC [click to play enlarge]

Suomi NPP VIIRS Ash Probability, Ash Height, Ash Loading and Ash Effective Radius at 1154 UTC [click to play enlarge]

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).

Meteosat-11 Split Window (11.12 µm) Brightness Temperature Difference images [click to play animation]

Meteosat-11 Split Window (11.12 µm) Brightness Temperature Difference images [click to play animation]

Eruption of the Anak Krakatau volcano in Indonesia

December 22nd, 2018 |

Himawari-8

Himawari-8 “Clean” Infrared Window (10.4 µm) images, with hourly plots of surface reports from Jakarta (station identifier WIII) [click to play animation | MP4]

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).

Plots of rawinsonde data from Jakarta, Indonesia [click to enlarge]

Plots of rawinsonde data from Jakarta, Indonesia [click to enlarge]

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.

Himawari-8 "Red" Visible (0.64 µm) images. with hourly plots of surface reports [click to play animation | MP4]

Himawari-8 “Red” Visible (0.64 µm) images, with hourly plots of surface reports from Jakarta (station identifier WIII) [click to play animation | MP4]

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.

Himawari-8 Ash Height retrievals [click to play animation]

Himawari-8 Ash Height retrievals [click to play animation]

Himawari-8 Ash Loading retrievals [click to play animation]

Himawari-8 Ash Loading retrievals [click to play animation]

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.

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 0610 UTC [click to enlarge]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 0610 UTC [click to enlarge]

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).

Infrared Window images from NOAA-20 VIIRS (11.45 µm) and Himawari-8 AHI (10.4 µm) [click to enlarge]

0610 UTC Infrared Window images from NOAA-20 VIIRS (11.45 µm) and Himawari-8 AHI (10.4 µm) [click to enlarge]

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


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.

Himawari-8

Himawari-8 “Red” Visible (0.64 µm, top) and “Clean” Infrared Window (10.4 µm, bottom) images [click to play animation | MP4]

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

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images [click to enlarge]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images [click to enlarge]

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.

Himawari-8

Himawari-8 “Clean” Infrared Window (10.4 µm) images, with hourly surface report plots from Jakarta WIII {click to play animation | MP4]

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

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images [click to enlarge]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images [click to enlarge]

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.

NOAA-20 VIIRS Infrared Window (11.45 µm) image [click to enlarge]

NOAA-20 VIIRS Infrared Window (11.45 µm) image [click to enlarge]

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.

Himawari-8

Himawari-8 “Clean” Infrared Window (10.4 µm) images, 22-25 December [click to play MP4 animation]

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

Himawari-8 "Clean" Infrared Window (10.4 µm) images, 22-28 December [click to play MP4 animation]

Himawari-8 “Clean” Infrared Window (10.4 µm) images, 22-28 December [click to play MP4 animation]

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).

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images [click to enlarge]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images [click to enlarge]



Satellite signatures of a meteor in the Bering Sea

December 18th, 2018 |

Himawari-8

Himawari-8 “Red” Visible (0.64 µm) images [click to play animation | MP4]

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).

Himawari-8 "Red" Visible (0.64 µm) and Shortwave Infrared (3.9 µm) images at 2350 UTC [click to enlarge]

Himawari-8 “Red” Visible (0.64 µm) and Shortwave Infrared (3.9 µm) images at 2350 UTC [click to enlarge]

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 "Red" Visible (0.64 µm) images [click to play MP4 animation | MP4]

GOES-17 “Red” Visible (0.64 µm) images [click to play animation | MP4]

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